A tandem-flow assembly for the chemiluminometric determination of hydroquinone

A direct chemiluminescent procedure for determination of hydroquinone based on the emergent flow methodology known as multicommutation or tandem-flow is presented for first time. The manifold was based on a set of three channels and three solenoid valves; and, the determination was performed at 60degreesC and at flow-rate of 7.5 ml min(-1). The complete cycle lasted 35 s, which resulted in a sample flow trough of 103 h(-1). The chemical process was the hydroquinone oxidation with the system sulphuric acid-potassium permanganate; and the light emission was clearly enhanced by the presence of quinine sulphate and benzalkonium chloride reaching a detection limit of 30 Rg l(-1). The dynamic int…

Selective chlorine determination by gas diffusion in a tandem flow assembly and spectrophotometric detection with o-dianisidine

Abstract A fast, selective, sensitive and automated method for determination of free chlorine in industrial formulations and water samples is proposed. The automation of the flow assembly is based on the “tandem flow” approach, which uses a set of solenoid valves acting as independent switches. The operating cycle for obtaining a typical analytical transient signal can easily be programmed by means of friendly software running in the Windows environment. The manifold is provided with a gas diffusion unit which permits the removal of interfering species as well as concentrating the chlorine. The determination of chlorine is performed on the basis of the oxidation of o-dianisidine as the colo…

Simultaneous dissolution profiles of two drugs, sulfadiazine-trimethoprim and amitriptyline-perphenazine, in solid oral dosage forms by a FIA manifold provided with a single spectrophotometric detector

The simultaneous determination of two dissolution profiles with the aid of a Flow Injection Analysis assembly has been applied to: (a) sulfadiazine-trimethoprim in tablets and (b) amitriptyline-perphenazine in sugar coated pills. The selected combinations are drugs which have overlapping UV-vis spectra. The officially proposed procedure from the pharmacopoeias has been adapted for the FIA methodology and derivative spectrophotometry and zero crossing. Preliminary experiments on the suitability of the simultaneous determination of both drugs were performed. The empirical profiles were adjusted by regression analysis using different approaches. The 3-parameter plot method was finally selected…

Simultaneous Determination of Adrenaline and Noradrenaline by First Derivative Spectrophotometry in a Fia Assembly

Abstract This article deals with the design of an unsegmented-flow injection manifold for the simultaneous determination of adrenaline and noradrenaline two structurally related compounds with overlapping spectra. An FIA manifold is proposed for the simultaneous determination in which the sample solution is directly injected into a carrier-reagent stream of aqueous NaOH. The selected wavelengths (first derivative) were 394 and 342 nm, for noradrenaline and adrenaline, respectively with an integration time of 0.4 s. The calibration graphs are linear over the range 2.0–30 ppm for both drugs. The method is applied to different synthetic mixtures of both drugs.

Oxidation of adrenaline and noradrenaline by solved molecular oxygen in a FIA assembly.

A simple and effective procedure is proposed for the study and simultaneous determination of adrenaline and noradrenaline. The fluorimetric determination of both substances is performed in a flow injection assembly and by oxidation of both drugs with the solved molecular oxygen. The influence of different parameters is empirically studied and the interpretation of the reaction mechanism is also added. The determination of adrenaline is monitored at 450 nm and the outputs at 520 nm correspond to the adrenaline and noradrenaline global amount; for both lectures lambda(exc) 329 nm. The influence of temperature is relevant and analytical determination occurred at 55 degrees C by immersing the s…

Extractive Spectrophotometric Determination of Ondansetron by Ion-Pair Formation with Bromocresol Green

Abstract An empirical spectrophotometric procedure for the determination of the antiemetic ondansetron is carried out. The method is based on the formation of a 1:1 ion pair with bromocresol green in the pH range over 3.2 – 4.4, extraction into chloroform layer and spectrophotometric measurement at 420.8 nm. The calibration graph is linear over the range 0.1 – 20 μg ml−1 ondansetron, with a relative standard deviation of 2.7%; the influence of foreign substances is also studied. The method is applied to ondansetron determination in human urine.

Continuous flow-injection-atomic absorption spectrometric method for the determination of Ondansetron

Abstract A flow-injection procedure for the indirect determination of the new drug Ondansetron is proposed. The method is based on the reaction of the drug in an oxidative solid-phase reactor included in the flow assembly. The reactor was made by lead dioxide physically entrapped by polymerization; the released lead(II) was monitored by atomic absorption spectrometry at 217.0 nm. The procedure gave a linear calibration graph up to 20 μg ml−1 of Ondansetron with a sample throughput of 338 samples h−1.

Some observations on the spectrophotometric determination of nitrite using ergonovine-p-dimethylaminobenzaldehyde

Abstract The system ergonovine maleate-p-diethylaminobenzaldehyde in sulfuric acid media is applied to the kinetic-spectrophotometric determination of nitrite ions with competitive precision. The reaction rate is strongly enhanced by the presence of nitrite or ferric ions, being the nitrite in the “promoting” role of the reaction. Linear calibration plots are obtained for nitrite concentration ranges 0.3–2.4 ppm or 0.66–6 ppb. The influence of foreign compounds is also established.

Inhibition of the system luminol-H2O2-Fe(CN)63− chemiluminescence by the Mn(II) indirect determination of isoniazid in a pharmaceutical formulation

A flow injection procedure for the indirect chemiluminescent determination of isoniazid is proposed. The method is performed in a flow-injection manifold provided with a solid-phase reactor. The reactor was made from manganese dioxide physically entrapped by polymerization; the redox reaction isoniazid-manganese dioxide released Mn(II) which was monitored through its inhibitory effect on the reaction between luminol and hydrogen peroxide in presence of potassium hexacyanoferrate (III). The procedure resulted in a linear calibration graph over the range 5-15 mg/L of isoniazid with a sample throughput of 43 samples/h. The influence of foreign compounds was studied and the method was applied t…

Enhanced chemiluminescent determination of chloramphenicol and related nitro compounds by ‘on-line’ photochemical reaction

The viability of tandem photochemical reaction-chemiluminescence detection was studied for a heterogeneous family of nitro compounds using chloramphenicol as a test substance. The 'on-line' chemical photodegradation of chloramphenicol was performed in a flow injection assembly by using a photoreactor consisting of a 725 cm x 0.5 mm id piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol was detected by oxidizing photo-fragments from the parent compound and their subsequent reaction with a luminol-Co(II) system. The calibration graph was linear up to 3 x 10(-5) mol l-1 chloramphenicol, the limit of detection was 3 x 10(-9) mol l-1, the relative s…

Theoretical prediction of the chemiluminescence behaviour of the ergot alkaloids

Abstract The present manuscript is dealing with the application of molecular connectivity calculations to predict the chemiluminescent behaviour of ergot alkaloids when they react with common strong oxidants in liquid phase. Twenty compounds were theoretically studied by means of a discriminant equation formerly published, being 19 of them predicted as chemiluminescent with a high probability. Empirical confirmation of the chemiluminometric behaviour is performed with the few soluble and commercially available ergot alkaloids. On the basis of these results, a new FIA-direct chemiluminescent method is proposed for the determination of the ergot presenting the higher light emission, the pharm…

Molecular connectivity as a relevant new tool for predicting analytical behavior: A survey of chemiluminescence and chromatography

Abstract We present a critical presentation and discussion on molecular connectivity applied to analytical fields, giving special attention to predicting the chemiluminescent behavior of pharmaceuticals and pesticides. Molecular connectivity has been largely applied to predict the therapeutic effects of pharmaceuticals and rarely to predictions in analytical chemistry – basically to chromatographic processes and recently to liquid-phase chemiluminescence.

FI-chemiluminometric study of thiazides by on-line photochemical reaction

The present manuscript deals with a simple and sensitive flow-injection method for the chemiluminescent determination of thiazides. The method is based on the on-line photodegradation and chemiluminescent determination of the resulting photo-fragments. The on-line photodegradation is performed in basic medium by using a photoreactor consisting of a 550 cm long x 0.8 mm ID piece of PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. The determination of the photo-irradiated thiazides is performed by a chemiluminescent oxidative reaction with Ce(IV) in sulphuric acid medium. A heterogeneous group of thiazides (indapamide, metolazone, hydroflumethiazide, chlorthalidone and be…

Flow Methods in Pharmaceutical Analysis

Fluorimetric determination of captopril by flow injection analysis

A flow injection analysis procedure is proposed for the determination of captopril. The sample solution was directly injected into the carrier-reagent stream which was prepared by a solution of ceric ions in 0.25 M sulfuric acid. The procedure is based on the fluorimetric monitoring of the formed Ce(III). Chemical, FIA, and instrumental parameters were optimized and the procedure is applied to the captopril determination in pharmaceutical formulations with competitive precision and adequate accuracy.

Enhanced flow-injection–chemiluminometric determination of sulphonamides by on-line photochemical reaction

Abstract The viability of the tandem photochemical reaction-chemiluminescence detection has been studied for an heterogeneous group of sulphonamides (sulphamethoxazole, sulphadiazine, sulphamerazine, sulphamethoxypyridazine, sulphacetamide, sulphadimidine, sulphanilamide, sulphathiazole and sulphaguanidine) using sulphamethoxazole (whose chemiluminescent behaviour has not been previously reported) as a test substance. The ‘on-line’ photochemical-reaction of sulphonamides provides an enhancing influence on the chemiluminometric response of the drugs during their oxidation by potassium permanganate in sulphuric acid medium (sulphamethoxazole, sulphacetamide, sulphadimidine and sulphanilamide …

Study of various indicating redox systems on the indirect flow-injection biamperometric determination of pharmaceuticals

Abstract The reversible redox couples (Fe(III)/Fe(II); Ce(IV)/Ce(III); Fe(CN) 6 3– /Fe(CN) 6 4− ; I 2 /I − ; Br 2 /Br − and VO 3 − /VO 2+ ) were studied as indicating redox systems for biamperometric determination of paracetamol in a flow injection assembly. Considering the selectivity of assayed systems against excipients and antioxidants that typically are presented in pharmaceutical formulations (e.g. sucrose, glucose, ascorbic acid and hydrogen sulphite) the systems Fe(III)/Fe(II) and VO 3 − /VO 2+ were selected for the determination of the drug. The sample was injected into a carrier which merged with the oxidant stream where the drug was oxidised by excess oxidant. The observed signal…

Prediction of the chemiluminescent behavior of pharmaceuticals and pesticides.

The present paper deals with the first attempt to apply molecular connectivity calculations to predict a chemical property with analytical usefulness: the chemiluminescent behavior of substances when reacted with common oxidants in a liquid phase. Preliminary evidence when searching for new direct CL methods consisted of the examination of analyte reaction with a wide range of oxidants and media. This task, which results in time-consuming and trial-and-error expensive procedures, is necessary due to ensure empirical or theoretical rules for CL prediction are available. On the other hand, in quantitative structure-activity relationship studies, molecular connectivity is a topological method …

Photo-induced chemiluminescence-based determination of diphenamid by using a multicommuted flow system

This manuscript deals with the application of molecular connectivity calculations to predict the photo-induced chemiluminescent behaviour of the family of herbicides grouped as amides. Several compounds of this group were theoretically studied by means of a general discriminant equation formerly obtained, being 18 of them (plus eight from the chloroacetanilide sub-group) predicted with a high probability as photo-induced chemiluminescent. Empirical confirmation of the chemiluminometric behaviour was performed with some few commercially available amide herbicides. On the basis of these results, a new multicommutation-photo-chemiluminescent method is proposed for the determination of the diph…

SIGNAL PROCESSING ALGORITHM FOR SCHLIEREN EFFECT CORRECTION IN FLOW ANALYSIS

Due to the radial refractive index gradients that sometimes develop in flow cells during the travelling of the samples through them, the absorbance records obtained in such conditions have a strange shape, particularly at low analyte levels. To correct this phenomenon, called Schlieren effect, a simple and reliable signal processing algorithm is described in correlation to the detector characteristics of noise. The algorithm is illustrated in nitrite and nitrate determinations with proflavin from more real samples. It has a solid theoretical support and involves the subtraction from the sample records of a smoothed signal, acquired by working with a blank solution.

Determination of promethazine hydrochloride with bromophenol blue by a turbidimetric method and flow injection analysis

Abstract A flow injection analysis procedure for the turbidimetric determination of promethazine is proposed. The sample solution is injected directly into the carrier reagent stream, which is composed of 1.16 × 10 −3 M bromophenol blue at pH 1.20. The calibration graph is linear over the range 25–197 ppm of promethazine. The influence of some foreign substances was also investigated. The method is applied to promethazine determination in a pharmaceutical formulation.

Flow-injection spectrophotometric determination of amino acids based on an immobilised copper(II) -zincon system

Abstract The flow-injection spectrophotometric determination of different amino acids was carried out by reaction with copper(II) ions entrapped in a polymeric material and filling a packed-bed reactor; the released copper(II), complexed with the amino acid, reacted with zincon in a basic medium producing a blue colour that was monitored at 600 nm. The method was applied to determine the contents of different amino acids in pharmaceutical formulations. The calibration graph for glycine was linear over the range 0.5–20 μg ml −1 with a relative standard deviation of 0.8% ( n = 6) at 10 μg ml −1 and a sample throughput of 108 h −1 .

New flow-multicommutation method for the photo-chemiluminometric determination of the carbamate pesticide asulam

This paper deals with a straightforward automated method for the determination of asulam in water based on the use of a flow manifold including three computer-controlled solenoid valves. The method involves irradiating on an aqueous solution of asulam in glycine buffer at pH 8.3 with UV light during 90 s, then follows the oxidation with potassium permanganate in a sulphuric medium and chemiluminescence-based detection of the resulting photoproducts. The limit of detection thus achieved is 40 mug l(-1). The detector response is linear up to a 5 mg l(-1) asulam concentration and the throughput is 30 samples h(-1). In parallel tests, oxidation with alkaline ferricyanide was also assessed and t…

Spectrophotometric and Fluorimetric Determination of 9-Amino Acridine by Flow Injection Analysis

Abstract The spectrophotometric and fluorimetric determination of 9-amino acridine is carried out by means of the FIA procedures and on the basis of its own color or fluorescence. The methanol used as a carrier stream resulted in a significative increase in sensitivity and sample throughput. The method is applied to the drug determination in pharmaceutical formulations.

Fluorometric determination of diphenhydramine by flow-injection analysis

A sensitive, rapid and simple flow injection procedure for the determination of diphenhydramine has been designed based on a fluorometric approach. An aqueous solution of diphenhydramine is injected into a carrierreagent stream containing Ce(IV) in dilute sulphuric acid and the fluorescence intensity of the Ce(III) produced is monitored. Chemical, FIA and instrumental variables were optimized. Analytical features of the method are: linear range 0.2–2 ppm, precision 0.7%, sample throughput 80/h. The influence of some foreign substances which can be found in typical pharmaceutical samples containing diphenhydramine was also investigated. The diphenhydramine content of a pharmaceutical prepara…

On-line photoreaction and fluorimetric determination of diazepam.

Determination of levamisole hydrochloride with HgI(2-)4 by a turbidimetric method and flow-injection analysis.

Abstract This paper is concerned with the use of ion-association compounds in the analysis of pharmaceutical samples by FIA. The usual extraction into an organic phase is avoided by using turbidimetric detection. Determination of levamisole with HgI2−4 has been developed as a practical example: the experimental variables were optimized by the modified simplex method. The calibration graph is linear over the levamisole concentration range 7–32 μ g ml . The reproducibility (rsd) and injection sample rate are 0.9% and 80/hr, respectively.

Flow-injection spectrofluorimetric determination of paracetamol

Abstract A flow-injection spectrofluorimetric determination of paracetamol is reported, based on the oxidation of the analyte with potassium hexacyanoferrate(III) immobilized on an anion-exchange resin, the fluorescence being enhanced with N,N′-dimethylformamide. Concentrations of paracetamol in the range 0.04–17.60 mg l−1 are determined with a relative standard deviation of 1.5%. The injection rate is 25 samples h−1. The influence of foreign species and the determination of paracetamol in several pharamaceutical formulations are also reported.

Chemiluminometric determination of the pesticide 3-indolyl acetic acid by a flow injection analysis assembly

Abstract A new method is proposed for the chemiluminescent determination of the pesticide 3-indolyl acetic acid by means of an flow injection analysis system. The chemiluminescence emission is obtained by oxidation of the analyte with Ce (IV) in nitric acid and presence of β-cyclodextrine. The continuous-flow method allows the determination of 159 samples h−1 of 3-indolyl acetic acid in an interval of concentrations over the range 0.5–15.0 mg l−1. The limit of detection was 0.1 μg l−1 and the R.S.D. (n, 17) at 2.0 mg l−1 of the pesticide level was 2.7%. The method was applied to water samples.

Photochemical Derivatization and Fluorimetric Determination of Promethazine in a FIA Assembly

Abstract The flow injection fluorimetric determination of promethazine is carried out by on-line photoderivatization. The PTFE tubing is helically coiled around the lamp. An analytical procedure is proposed by using aqueous solution as carrier stream: the calibration graph is linear over the range 0.05 - 20 ppm. The influence of foreign compounds is studied and the method is applied to promethazine determination in pharmaceutical formulations.

Determination of Amitriptyline with Bromocresol Purple and Flow Injection Analysis

Abstract The study of some amitriptyline-dye systems was carried out in order to determine the best precipitate for the turbidimetric determination of amitriptyline using FIA. The reagent selected was bromocresol purple. The chemical and FIA variables were optimized. The calibration graph was linear over the concentration range 30.0–200.0 ppm of amitriptyline hydrochloride. Some interfering substances were also investigated.

FIA-fluorimetric determination of adrenaline in pharmaceutical formulations by oxidation with molecular oxygen

The fluorimetric determination of adrenaline is carried out in a continuous-flow assembly and by means of the molecular dissolved oxygen. The sample solution merges with an NaOH stream, then the resulting mixture is heated at 73 °C and led to the flow-cell of the fluorimeter. The flow-assembly is very simple and the procedure is quick (107 samples h−1) reproducible (R.S.D. 0.6%), selective and suitable to be applied to determination of adrenaline in formulations. Calibrations graph are linear over the ranges 0.05–15 and 20–40 mgl−1.

High-pressure flow-injection assembly. Indirect determination of glycine by atomic absorption spectrometry.

A procedure for the determination of glycine is described. The method is based on the reaction of the analyte with finely powdered, solid copper(II) carbonate in a continuous-flow assembly. The optimum experimental conditions of pH, temperature, sample volume, flow-rate, column length and internal diameter, and the linear range of calibration, were studied. Interference from foreign substances that accompany this amino acid in pharmaceutical formulations was studied, and the method was applied to the determination of glycine.

Automated simultaneous triple dissolution profiles of two drugs, sulphamethoxazole-trimethoprim and hydrochlorothiazide-captopril in solid oral dosage forms by a multicommutation flow-assembly and derivative spectrophotometry.

This article deals with the simultaneous determination of three dissolution profiles with the aid of the new and emerging continuous-flow methodology known as multicommutation. This methodology is based on a flow network of a set of solenoid valves controlled by the computer and acting as independent multicommutators to allow the easy and automated control of flowing solutions. The obtained three dissolution profiles from one dosage form are the whole formulation profile or "global profile" recommended by pharmacopoeias, and, at same time, are recorded two "individual" profiles from two drugs present in the formulation. This is the second attempt to obtain simultaneously three dissolution p…

In situ generation of Co(II) by use of a solid-phase reactor in an FIA assembly for the spectrophotometric determination of penicillamine

[EN] A flow injection analysis (FIA) manifold for the determination of penicillamine in pharmaceutical preparations is proposed. The manifold includes a solid-phase reactor for the in situ production of the derivatizing reagent, Co(II) ion, which forms a coloured complex with penicillamine in an alkaline medium. The reactor is prepared by natural immobilization of cobalt carbonate on a polymer matrix, which endows it with a high mechanical and microbiological stability. The cobalt released by passage of a 5 x 10(-4) Mol l(-1) sulphuric acid stream at a flow-rate of 2.3 ml min(-1) is merged with a volume of 314 mu l of sample containing penicillamine in ammonium-ammonia buffer at pH 9.5 to m…

Immobilization of Hexacyanoferrate (III) for a Flow Injection-Spectrophotometric Determination of Promazine

Abstract An automated flow injection method for the determination of promazine is described. The method is based on the oxidation of promazine by hexacyanoferrate (III) and spectrophotometric monitorization of oxidized drug. The chemical and FIA variables were optimized. The calibration graph was linear over the concentration range 2,5–25 ppm of promazine hydrochloride. Some interfering substances were also investigated. The method was applied for the determination of promazine in pharmaceutical formulations.

Determination of the herbicide benfuresate by its photo-induced chemiluminescence using flow multicommutation methodology.

The present paper deals with an analytical strategy based on coupling photo-induced chemiluminescence in a multicommutation continuous-flow methodology for the determination of the herbicide benfuresate. The solenoid valve inserted as small segments of the analyte solution was sequentially alternated with segments of the NaOH solution for adjusting the medium for the photodegradation. Both flow rates (sample and medium) were adjusted to required time for photodegradation, 90 s; and then, the resulting solution was also sequentially inserted as segments alternated with segments of the oxidizing solution system, hexacyanoferrate (III) in alkaline medium. The calibration range from 1 microg L(…

Spectrophotometric determination of promethazine by flow injection analysis and oxidation by CeIV

A flow injection analysis (FIA) procedure is proposed for the determination of promethazine. The sample solution is directly injected into the carrier-reagent stream which comprises a solution of ceric ions in a sulphuric acid medium. The absorbance at 514 nm from the red colour developed by the oxidation of promethazine is measured. Effects of foreign substances have been investigated and the procedure has been applied to the determination of promethazine in a pharmaceutical formulation (tablets).

FIA-spectrophotometric determination of N-substituted phenothiazine derivatives by oxidation with a solid-phase reactor of manganese dioxide incorporated in polyester resin beads

Abstract The determination of several N -substituted phenothiazine derivatives was carried out by the reaction of the drug with managanese dioxide entrapped in a polymeric material in a packed-bed reactor; the oxidized drug was monitored at λ max . The calibration graph is linear over the range 5–50 μg/ml of phenothiazine derivatives with a relative standard deviation of 0.5–1% (at 10 μg/ml) and sample throughput of 40–48 h −1 . The influence of foreign compounds was studied and the method was applied to the determination of six different phenothiazine derivatives in pharmaceutical formulations.

Photo‐Induced Chemiluminometric Determination of Acrolein in a Multicommutation Flow Assembly

Abstract This paper deals with the determination of acrolein based on a strategy provided with a sensitive detection, the chemiluminescence; a “clean chemical” analyte treatment, the on‐line UV‐irradiation; and, a simple and quick automated system, the emergent multicommutation continuous‐flow methodology. The pesticide solution is irradiated (stopped‐flow) for 30 s; then, the resulting solution is introduced to the flow‐cell after being alternated with segments of the stream formed by potassium permanganate in strong acid solution and ethanol segments. The calibration range, from 1 to 1 mg l−1, resulted in a linear behavior over the range 5–100 µg l−1 and fitting the linear equation: I=75.…

Direct flow injection chemiluminescence determination of salicylamide

Abstract A new direct flow injection chemiluminescence method is proposed for the determination of salicylamide, based upon the oxidation of the drug by potassium permanganate in dilute sulphuric acid. The calibration graph is linear over the range 20 ng ml−1 (30 limit of detection)–8 μg ml−1 salicylamide, with a relative standard deviation (n=50, 0.5 μg ml−1) of 1.7%. The average sample insertion rate is 142 h−1. The influence of relevant foreign compounds is found to be relatively slight. The method is applied to the determination of salicylamide in a pharmaceutical formulation and human urine.

Quantitative colorimetric-imaging analysis of nickel in iron meteorites.

A quantitative analytical imaging approach for determining the nickel content of metallic meteorites is proposed. The approach uses a digital image of a series of standard solutions of the nickel-dimethylglyoxime coloured chelate and a meteorite sample solution subjected to the same treatment as the nickel standards for quantitation. The image is processed with suitable software to assign a colour-dependent numerical value (analytical signal) to each standard. Such a value is directly proportional to the analyte concentration, which facilitates construction of a calibration graph where the value for the unknown sample can be interpolated to calculate the nickel content of the meteorite. The…

Theoretical prediction of the photoinduced chemiluminescence of pesticides

Although it is relatively easy to find chemiluminescent (CL) molecules working on the field of direct liquid phase (especially employing strong oxidants), the molecules found as chemiluminescent are normally very weak CL compounds for developing suitable analytical CL-procedures. Therefore, it is mandatory to develop new strategies to enhance in a simple way the native chemiluminescence of such a compounds, and even to increase the number of compounds to be determined by direct chemiluminescence. Photoinduced chemiluminescence (Ph-CL) results in a simple and easily on-line accessible strategy to solve these disadvantages. In the present paper, molecular connectivity, a topological method wh…

Entrapment of FePO4 in a polymeric matrix and their application to FIA-spectrophotometric determination of thioridazine and chlorpromazine in pharmaceutical formulations

Determination of Phenol by Preconcentration‐Direct Chemiluminescence in a FIA Assembly

Abstract The determination of phenol in water samples is proposed with the aid of a flow‐injection system. The analytical procedure is based on the direct chemiluminometric emission by oxidation of the analyte with potassium permanganate in acidic medium. The flow assembly is provided with a solid‐phase reactor filled with a resin type XAD‐4 for analyte preconcentration. A large study of potential interferences, namely, amino acids reaching water through degradation of organic matter; metals and inorganic metal ions typically present in water interfering with the CL emission of the parent compound, was performed. The calibration graph was linear over the phenol concentration range 1.0–20.0 …

Flow injection biamperometric determination of metronidazole with on-line photodegradation

Abstract The determination of metronidazole is performed in a flow injection assembly, provided with a 40 W low pressure mercury lamp and a home-made biamperometric flow-cell furnished with two platinum electrodes polarized at 100 mV. The sample solution after being irradiated is inserted into a pure water stream. It then merges with an in situ mixed solution containing potassium iodide in sulphuric acid. The calibration graph was linear over the range 0.2–8.0 mg l −1 metronidazole; the 3 σ limit of detection was 0.008 mg l −1 ; the relative standard deviation was 0.6% (for 4 mg l −1 n  = 13) and the sample throughput 50 h −1 . The influence of foreign compounds is slight and the method is …

On-line photochemical derivatization and flow-injection spectrophotometric determination of ergonovine maleate

Abstract A flow-injection manifold is proposed for the on-line photochemical derivatization of ergonovine maleate with application to pharmaceutical formulations. The procedure is based on the reaction with p-dimethylaminobenzaldehyde in presence of iron(III) and sulphuric acid medium. The reaction rate is improved by irradiation of the solution with a mercury lamp (254.0 nm). The calibration graph is linear over the range 3–74 μg ml−1 ergonovine, with a mid-range R.S.D. of 1.7% and a sample throughput of 34 h−1. The influence of foreign compounds was tested.

Continuous-flow spectrophotometric determination of sulfadiazine by diazotisation with in situ preparation of nitrite

Abstract Nitrite is prepared in situ for the determination of sulfadiazine. The method is based on solid-phase reduction of copperized cadmium of nitrate; the nitrite reagent merges with the sample stream in hydrochloric acid medium and the resulting mixture is injected into the water carrier, pure distilled water, and then merges with the N-(1-naphthyl)ethylendiamine reagent and is measured spectrophotometrically at 542.0 nm. The calibration graph is linear over the range 0.5–50 μg ml−1 sulfadiazine, mid-range R.S.D. = 0.3% (n = 5) and sample throughput 72 h−1. The procedure is applied to sulfadiazine determination in a pharmaceutical formulation and to in vitro dissolution studies of two …

Photo-induced chemiluminescence determination of the pesticide Buminafos by a Multicommutation flow-analysis assembly

Abstract The preliminary experiments in this paper deal with the photo-induced chemiluminescent behaviour of Buminafos family, after the experimental screening tests and several of them resulted positive, the herbicide Buminafos was selected to develop a new analytical method. The determination of Buminafos was performed with the aid of a Multicommutation (a solenoid valve set) assembly. The method involves the on-line photo-degradation of the analyte (stopped flow, 5 s) with the selected suitable medium (0.05% hydrogen peroxide) and its subsequent chemiluminescent oxidation by the potassium permanganate. Sample solution alternated segments with the photo-degradation medium; and, after the …

Spectrofluorimetric determination of emetine by flow injection using barium peroxide and UV derivatization

Abstract The flow-injection spectrofluorimetric determination of emetine was carried out by photoderivatization in the presence of barium peroxide, in a flow-injection assembly in which the PTFE tubing in the injection valve is helically coiled around the lamp. The sample solution merges with a barium peroxidephosphoric acid solution and then the resulting mixture is irradiated; pure distilled water is used as a carrier stream. The calibration graph is linear over the range 0.05–50 μ g ml −1 of emetine dihydrochloride. The influence of foreign compounds was studied and the method was applied to the determination of emetine in injection and human urine samples.

FI-on line photochemical reaction for direct chemiluminescence determination of photodegradated chloramphenicol.

Abstract A new, simple, clean and selective flow injection strategy based on the tandem photochemical reaction-chemiluminescence detection was applied to the determination of chloramphenicol. The determination is based on the on-line photodegradation of the drug in a glycine buffer at pH 8.8 by using a photoreactor consisting of 697 cm×0.5 mm PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. Photodegradated chloramphenicol is detected by direct chemiluminescence of resulting photo-fragments and their subsequent reaction with potassium permanganate in sulfuric acid medium as oxidant. The method allows the chemiluminescence determination of compounds which do not exhibit n…

Analytical strategy photodegradation/chemiluminescence/continuous-flow multicommutation methodology for the determination of the herbicide Propanil

The present paper is dealing with an analytical strategy based on coupling photodegradation, chemiluminescence and multicommutation continuous-flow methodology for the determination of the pesticide Propanil, a common herbicide. The pesticide solution is inserted as small segments sequentially alternated with segments of the solution for adjusting the suitable medium for the photodegradation. Both flow-rates (sample and medium) are adjusted to required time for photodegradation, 2.0 min; and then, the resulting solution is also sequentially inserted as segments alternated with segments of the oxidizing solutions system, 1.00 x 10(-4) mol 1(-1) potassium permanganate in 2.00 mol 1(-1) sulphu…

FIA-AAS determination of salicylic acid by a solid-phase reactor of copper carbonate incorporated in polyester resin beads.

Abstract The determination of salicylic acid was carried out by reaction of the drug with copper carbonate entrapped in a polymeric material in a solid-phase reactor; the released cupric ions were monitored by flame atomic absorption at 324.8 nm. The calibration graph is linear over the range 4.0–75 μg ml −1 of salicylic acid, with a relative standard deviation of less than 1.5% and a sample throughout of 257 h −1 . The influence of foreign compounds was studied and the method was applied to the determination of salicylic acid content in two different pharmaceutical formulations.

Spectrophotometric determination of nalidixic and pipemidic acids in a flow injection assembly with a solid-phase reactor as a highly stable reagent source

Abstract The flow-injection spectrophotometric determination of nalidixic (I) and pipemidic (II) acids were carried out by reaction with Fe(III) ions entrapped in a polymeric material and filling a packed-bed reactor; the released Fe(III) complexed with the quinolone is monitored at 426 nm. The method worked with a high reproducibility, even when using different reactors, days and solutions. Selectivity of the procedure was tested with different foreign compounds found in human urine as well as in pharmaceutical formulations containing both quinolones; no relevant interferences were observed. The calibration graph for (I) was linear over the range 1–250 μg ml −1 with a relative standard dev…

Prediction of the chemiluminescent behaviour of phenols and polyphenols.

Abstract A paper from this laboratory ‘J. Anal. Chem. 73 (2001) 4301’ was recently published and dealing with the first attempt to apply molecular connectivity calculations to predict a chemical property with analytical usefulness; namely, the chemiluminescent behaviour of substances when react with common strong oxidants in liquid phase. In the present work, the usefulness of molecular topology on the search for new chemiluminescent compounds is clearly demonstrated. The proposed discriminant equation, represented a success of 92.7% in the prediction. The present paper is the further step from the cited paper; it is dealing on the application of molecular connectivity calculations (former …

Photochemical-chemiliminometric determination of aldicarb in a fully automated multicommutation based flow-assembly

[EN] A sensitive and fully automated method for determination of aldicarb in technical formulations (Temik) and mineral waters is proposed. The automation of the flow-assembly is based on the multicommutation approach, which uses a set of solenoid valves acting as independent switchers. The operating cycle for obtaining a typical analytical transient signal can be easily programmed by means of a home-made software running in the Windows environment. The manifold is provided with a photoreactor consisting of a 150 cm long x 0.8 mm i.d. piece of PTFE tubing coiled around a 20 W low-pressure mercury lamp. The determination of aldicarb is performed on the basis of the iron(III) catalytic minera…

Chemiluminometric photo-induced determination of Strychnine in a Multicommutation flow assembly

This paper deals on the determination of Strychnine, a potent and dangerous pesticide and the analytical procedure is based on the photo-induced chemiluminescence of the pesticide by means of the Multicommutation continuous-flow methodology. Small segments of the pesticide solution were sequentially alternated with segments of the solution for adjusting the suitable medium for the photodegradation. The required time of UV irradiation was obtained by stopped-flow during 150 s; then, the resulting solution formed alternated segments with the oxidizing solution containing 5 × 10−3 mol l−1 Ce(IV) in 0.6 mol l−1 nitric acid. The calibration range, from 2 μg l−1 to 50 mg l−1, resulted in a linear…

Flow‐Injection Chemiluminescent Determination of Thiamine in Pharmaceutical Samples by On‐line Photodegradation

Abstract A simple, sensitive, and precise method for the determination of thiamine hydrochloride in a flow‐injection system is described. The method is based on the UV irradiation of thiamine in acid medium. Then, the photo‐fragments are oxidized by permanganate in acid medium, and the resultant chemiluminescent intensity is measured. The optimum conditions for the photoreaction and for the chemiluminescence emission were investigated. The method allows the determination of thiamine, over the range 0.05(LOD)–84 mg · l−1, with a throughput of 30 h−1, and a RSD (n, 20) at 20 and 0.5 mg · l−1 of the thiamine level of 2.5 and 1.3%, respectively. The method was applied to pharmaceutical preparat…

Theoretical prediction of the native fluorescence of pharmaceuticals

At present, to search fluorescent compounds or to increase the native fluorescence is an active research line specially and not only with analytical purposes. On some analytical areas and from the early times of applications of fluorescence (mid-fifties) the fluorimeter was defined as the suitable detector for determination of pharmaceuticals and subsequently, this detection mode has been widely applied. Therefore, it is mandatory to develop new strategies to discover or to enhance in a simple way the native fluorescence of organic compounds to increase the number of analytes to be determined by direct fluorescence. In the present paper are studied further applications of a new tool suitabl…

Spectrophotometric determination of chlorhexidine with bromocresol green by flow-injection and manual methods

Abstract A spectrophotometric study of the chlorhexidine/bromocresol green/Triton X-100 system is reported; at pH 5.3, both 2:1 and 1:1 bromocresol green/chlorhexidine complexes are formed. In the manual spectrophotometric method, Beer's law is obeyed for chlorhexidine concentrations of 2.9–32.2 μg ml −1 (r.s.d. 0.4–1.3%); the molar absorptivity is 12 500 l mol −1 cm −1 . In the flow-injection method, the calibration graph is linear for the chlorhexidine range 23.0–83.9 μg ml −1 (r.s.d. 0.8%); the injection is ca. 60 h −1 . Benzocaine, acetylsalicylic acid, ascorbic acid and sucrose are tolerated at 10 −2 −10 −3 M levels. Hibitane 5% was analyzed successfully.

Determination of the flavor enhancer maltol through a FIA — direct chemiluminescence procedure

Abstract A new FIA — direct chemiluminescence method is proposed for the determination of maltol, based upon the oxidation of the food additive by KMnO 4 in sulfuric acid medium at 80°C enhanced by hexadecylpyridinium chloride (HD) and formic acid (HCOOH). The calibration graph is linear over the range 0.5–4.0 mg l −1 of maltol, with a R.S.D. ( n =50, 0.5 mg l −1 ) of 2.9%, LOD ( s / n =3) of 10 mg l −1 and sample throughput of 153 h −1 .

Selective flow-injection biamperometric determination of sulfur-containing amino acids and structurally related compounds

Abstract A simple and selective flow-injection method for the determination of cysteine and methionine is proposed. The method is based on the reaction of the amino acid with chloramine-T and the subsequent reaction of the excess of chloramine-T with an acidic solution of iodide producing a stoichiometric amount of tri-iodide (diminution of the flow-injection analysis (FIA) peak) which is determined biamperometrically using two platinum electrodes polarized at 100 mV. The calibration graph is linear up to 10 μg ml−1 of cysteine and 30 μg ml−1 of methionine; the limit of detection is 0.06 and 0.1 μg ml−1; the repeatability (also as percent of a series of 70 continuous FIA peaks of 5 μg ml−1 …

Determination of diphenhydramine hydrochloride by flow injection with Bromophenol Blue and turbidimetric measurement

The study of a number of diphenhydramine-dye systems was carried out in order to determine the most suitable precipitate for the turbidimetric determination of diphenhydramine using flow injection (FI). The reagent selected was Bromophenol Blue. The chemical and FI variables were optimised. The calibration graph was linear over the concentration range 50-230 p.p.m. of diphenhydramine hydrochloride. A number of interfering substances were also investigated.

Determination of nitrite by inhibition of the chemiluminescence of acriflavine in a flow-injection assembly

The indirect determination of nitrite was performed with a flow-injection assembly on the basis of the inhibition of the analytical output obtained in a luminometer by oxidation of acriflavine. The acriflavine solution merged with the nitrite and the resulting mixture was injected into a pure water stream. This solution merged with the oxidant solution (potassium permanganate in sulfuric acid medium) and the resulting chemiluminiscence was affected (inhibited) by the presence of nitrite after reaction with the aminoacridine. The method was applicable over the range 10–800 μg l−1 of nitrite with a correlation coefficient of 0.9960. The relative standard deviation was 1.4% and the throughput …

Spectrophotometric determination of promazine with an oxidative column in FIA manifolds

Abstract A simple flow-injection spectrophotometric method for the determination of promazine is described. The two proposed procedures are based on the oxidation of analyte with a manganese dioxide column. Concentrations of promazine in the ranges 2–20 and 1–6 are determined with a relative standard deviation of 1.0%. The injection rates are 62 and 80 samples h −1 , respectively. The influence of foreign species and the determination of promazine in a pharmaceutical formulation are also reported.

Immobilization of reagents by polymeric materials. Determination of metamizol

Abstract A method for immobilization of inorganic reagents, based on the dispersion of the reagent into an unsaturated polyester solution is applied to immobilization of lead dioxide. The obtained solid is of application in a flow-injection manifold for indirect atomic absorption determination of metamizol in pharmaceutical formulations. The procedure gives a linear calibration graph up to 6 ppm of metamizol with a relative standard deviation of 1.6% (3.0 mg/l) and a sample throughput of 72 hr−1.

Spectrofluorimetric Determination of Iproniazid and Isoniazid in a FIA System Provided with a Solid-Phase Reactor

Abstract A FIA assembly is proposed for the fluorimetric determination of iproniazid and isoniazid. The oxidation of both drugs is carried out by H2O2. The excess of reagent is destroyed and removed from the flow-injection manifold by means of a metallic copper reactor which acts as catalyst in the decomposition of H2O2 and a home made debubbler. The calibration graphs were linear up to 14 μg ml−1 and 10 μg ml−1 (n=6) for iproniazid and isoniazid, respectively, with limits of detection of 0.008 μg ml−1 and 0.005 μg ml−1. The sample throughput was 24 h−1 for both drugs. The influence of foreign compounds was studied and the procedure was applied to determination of iproniazid and isoniazid i…

‘In situ’ preparation of nitrous acid solutions by photoreduction in a flow assembly for analysis of pharmaceuticals

The solutions of nitrite ion, or nitrous acid, are frequently used as reagent in different analytical procedures and in pharmaceutical analysis. The low stability of the aqueous solutions of this reagent implies the tedious work of freshly prepared solutions every day and being kept in the refrigerator. In this paper, a photoreactor formed by a low pressure mercury lamp and nesting in a continuous-flow manifold is studied, tested, and proposed for the in situ reduction of nitrate solution into nitrite. The conversion into nitrite is reproducible and it has been successfully applied to determination of different drugs, mostly from the sulphonamide family, in an FIA assembly.

Indirect determination of paracetamol in pharmaceutical formulations by inhibition of the system luminol–H2O2–Fe(CN)63− chemiluminescence

After a large drug scanning, the system Luminol-H2O2-Fe(CN)6(3-) is proposed for first time for the indirect determination of paracetamol. The method is based on the oxidation of paracetamol by hexacyanoferrate (III) and the subsequent inhibitory effect on the reaction between luminol and hydrogen peroxide. The procedure resulted in a linear calibration graph over the range 2.5-12.5 microg ml(-1) of paracetamol with a sample throughput of 87 samples h(-1). The influence of foreign compounds was studied and, the method was applied to determination of the drug in three different pharmaceutical formulations.

Use of QSAR methods for predicting the chemiluminescent behaviour of organic compounds upon reaction with potassium permanganate in an acid medium

In previous work, molecular connectivity computations were successfully used to predict the chemiluminescent behaviour of organic compounds upon reaction with common strong oxidants and the native fluorescence too; both of them in a liquid phase. The obtained results were used to develop new analytical procedures to the given compounds. For the first time, connectivity methods were used for a purely analytical purpose. In this work, we went deeper into the knowledge of direct chemiluminescence processes by using molecular connectivity in the form of QSAR methods to predict the chemiluminescence intensity produced by reactions between organic compounds (pharmaceuticals mainly) and potassium …

Photo-induced chemiluminometric determination of Karbutilate in a continuous-flow Multicommutation assembly

The present paper deals with the chemiluminescent determination of the herbicide Karbutilate on the basis of its previous photodegradation by using a low-pressure Hg lamp as UV source in a continuous-flow multicommutation assembly (a solenoid valves set). The pesticide solution was segmented by a solenoid valve and sequentially alternated with segments of the 0.001 mol l(-1) of NaOH solution, the suitable media for the formation of photo-fragments; then it passes through the photo-reactor and was lead to the flow-cell after being divided in small segments which were sequentially alternated with the oxidizing system; 2 x 10(-5) mol l(-1) of potassium permanganate in 0.2% pyrophosphoric acid.…

Photo-Induced Luminescence

The present paper is a critical review dealing with the characteristics, reaction mechanisms and photoproducts, instrumentation and analytical applications of the photo-induced either chemiluminescence or fluorescence. Special attention is paid to the determination of pesticides by continuous-flow methodologies. The paper is divided into several sections covering the most relevant published papers.

Indirect Catalytic Spectrophotometric Determination of Metamizol Following Oxidation by Lead Dioxide Immobilized in A Polyester Resin Bed

Abstract A spectrophotometric-indirect procedure for the determination of metamizol is described. The method is based on the reaction of the drug in a solid-phase (lead dioxide immobilized in a polyester resin bed) in acidic media (perchloric acid 0.01 M as carrier). The lead dioxide reactor provides simultaneously an effective oxidation of the drug and a controlled liberation of Pb(II) which acts as catalyst on the reaction pyrogallol red-potassium persulphate; the oxidation of the red pyrogallol results in a less coloured solution. The decreased red colour (negative FIA peaks) is monitored at 520 nm. The calibration graph is linear in the interval 2–16 ppm in metamizol. The relative stand…

FIA-Chemiluminescence Determination of Acridine Yellow

Abstract The direct determination of yellow acridine is performed by a FIA assembly on the basis of the oxidation of the acridine. The acridine solution is injected into a pure water stream. This solution merges with the oxidant solution (KMnO4 in sulfuric acid medium) and the resulting chemiluminescence allows the method to be applied over the range 0.01–100 mg L−1 of acridine with a correlation coefficient of 0.9997. The relative standard deviation (%) is 1.6 and the sample throughput 60 h−1. The influence of foreign substances is also tested. The new method is applied to the determination of yellow acridine in waste waters.

Flow injection biamperometric determination of chloramine-T in environmental, pharmaceutical and veterinary samples

Abstract A flow injection assembly for the determination of chloramine-T is proposed. The sample (213 μl) is inserted into the carrier, de-ionized water flowing at 4.1 ml min−1. This carrier merges with a mixture of potassium iodide and sulphuric acid, and the resulting solution flows to the flow cell through a reactor 66 cm long. The chloramine-T oxidises the iodide to tri-iodide. The resulting iodide/iodine ratio is biamperometrically tested. The calibration graph is linear up to 65 μg ml−1 chloramine-T; the limit of detection is 0.5 μg ml−1; the relative standard deviation (r.s.d) of the calibration slope is 2.8% for a series of eight independent calibrations. The r.s.d. of a series of 7…

FIA-fluorimetric determination of thiamine.

A flow injection-fluorimetric determination of thiamine is reported. The procedure is based on the oxidation of the analyte with potassium hexacyanoferrate(III) immobilized on an anionic exchange resin; the fluorescence is monitored in aqueous basic solution. Concentrations of the vitamin of 0.1-4 ppm have been determined; the relative standard deviation was 1.8%. The injection rate was 28 samples/h. The influence of other substances and the determination of the drug in a pharmaceutical formulation are also reported.

Determination of the Herbicide Fluometuron by Photo‐induced Chemiluminescence in a Continuous‐flow Multicommutation Assembly

Abstract This study was dealing with the chemiluminometric determination of the selective herbicide Fluometuron or 1,1‐dimethyl‐3‐(α,α,α‐trifluoro‐m‐tolyl)urea, (C10H11F3N2O) with a molecular weight 232.29 belongs to the phenyl urea herbicides family. The analytical strategy is based on the continuous‐flow manifold, multicommutation and the analyte pre‐treatment, the photo‐degradation. The optimization of chemical (pH, medium, temperature, and organized media) and hydrodynamic parameters (volume of reagents and flow rate) was performed by univariant and multiparametric simplex procedure respectively. Analytical figures of merit and the effect of foreign substances were studied. The method r…

Flow injection-spectrophotometric determination of metoclopramide hydrochloride.

Abstract The determination of metoclopramide hydrochloride is spectrophotometrically determined by the Bratton-Marshall method in a flow injection assembly. The required nitrite is prepared on-line in the flow assembly by reducing a nitrate solution with the aid of a copperised cadmium solid-phase reactor. The calibration graph is linear over the range 0.5–85 mg l−1, with a relative standard deviation (RSD) of 0.89%, and sample throughput of 51 samples h−1. The method is easy and simple, and it is applied to determination of metoclopramide in some pharmaceutical formulations. The method eliminates the need for frequent preparation of unstable nitrite solutions.

Photoinduced chemiluminescence of pharmaceuticals

Abstract A screening test for the forward development of chemiluminescence systems able to determine pharmaceutical compounds is reported. The test is based on the on-line photodegradation of the drugs by using a photoreactor consisting of 697 cm × 0.5 mm PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. Photodegraded pharmaceuticals are detected by direct chemiluminescence of the resulting photofragments and their subsequent reaction with potassium permanganate in sulphuric acid medium as oxidant. The screening comprised 97 compounds with different molecular structures and relevant members of the most important families of pharmaceuticals are tested (amino acids, carbox…

Three simultaneous dissolution profiles on a solid pharmaceutical formulation by a FIA manifold provided with a single spectrophotometric detector.

This article deals with the simultaneous determination of three dissolution profiles in the same pharmaceutical formulation. The officially proposed procedure from the pharmacopoeias is adapted to the FIA methodology to obtain the officially recommended profile or "global profile", and two "individual" profiles, corresponding to dissolution rate of two different active principles present in the formulation; both drugs have overlapped UV-vis spectra. The simultaneous determination of several profiles is based on the derivative spectra and the zero crossing mathematical procedure for the "individual" profiles of an active principle; the "global" profile of the formulation is obtained from the…

Determination of tannic acid by direct chemiluminescence in a FIA assembly

The determination of tannic acid is performed in a FIA assembly on the basis of the analytical output obtained by oxidation of the acid. The analyte solution was daily prepared in a mixture of quinine as sensitiser and perchloric acid and it was injected into a pure water stream acting as a carrier. This solution merges with the mixture potassium permanganate in perchloric medium and the resulting chemiluminescence is monitored. The method was applied over the range 0.5-20 mg l(-1) of tannic acid with a LOD 100 mug l(-1). The reproducibility was 2.1% and the sample throughput 54 h(-1). The influence of foreign substances was studied and the new method is applied to the determination of tann…

Spectrophotometry: Pharmaceutical Applications

Pharmaceutical analysis is mainly focussed in drug analyses, in raw materials and pharmaceutical formulations, involving the determination of active components, impurities, excipients, content uniformity, solubility, dissolution rate and stability.

Determination of tyrosine through a FIA-direct chemiluminescence procedure.

A new FI-direct chemiluminescence method is proposed for the determination of tyrosine, based on the oxidation of the amino acid by K(3)Fe(CN)(6) in potassium hydroxide medium, at room temperature and enhanced by the presence of beta-cyclodextrin and formic acid. The dynamic range was linear over the range 1.0-10.0 mgl(-1). A large study of the influence of foreign compounds was performed, including amino acids; and, the method showed high selectivity. The reproducibility between days resulted in a rsd (in slope%) of 4.8 and the repeatability with a rsd (n=50, 10.0 mgl(-1)) of 3.1%, the LOD (s/n=3) was 50 mugl(-1) and sample throughput 98 h(-1).

FIA-fluorimetric determination of adrenaline by oxidation with a solid-phase reactor of manganese dioxide incorporated in polyester resin beads

Abstract The FIA-spectrofluorimetric determination of adrenaline was carried out by reaction of the drug with manganese dioxide entrapped in a polymeric material in a solid-phase reactor; the oxidized drug was monitored fluorimetrically at 540 nm (Ioxg. 330.0 nm). The calibration graph for adrenaline was linear over the range 0.5 - 20 μg ml−1 with a relative standard deviation of 2.0% (at 5 ug ml−1) and the sample throughput of 65 h−1. The influence of foreign compounds was studied and the method was applied to the determination of adrenaline content in a pharmaceutical formulation . ∗Present address: Institut of Chemistry, Warsawa University, Bialystok Branch, Bialystok, Poland.

Flow-chemiluminescence: a growing modality of pharmaceutical analysis.

The present article deals with a review of the applications of the chemiluminescence to pharmaceutical analyses by using continuous-flow assemblies. A comprehensive study on the fundamentals of the chemiluminescence is also included.

Application of sequential injection analysis to pharmaceutical analysis.

Sequential injection analysis is a well established tool for automation of pharmaceutical analysis. A short historical background of this technique is given as well as a brief discussion on the basic principles and potentials. The current applications of SIA in the pharmaceutical analysis are also described and discussed. The manifolds developed offer good analytical characteristics and are suitable for analysis of drug formulations, process analysis, drug-dissolution, drug-release testing and functional assays for screening potential drugs. The results obtained are in good agreement with those furnished by the application of the reference methods presented in the pharmacopoeias.

Photo-induced fluorescence of magnesium derivatives of tetracycline antibiotics in wastewater samples

Abstract An analytical strategy, for the determination of tetracyclines (TCs), based on a HPLC system coupled with a photo-reactor followed by post-column derivatization was developed. Higher fluorescence emission after coupling the resulting photo-fragments with magnesium ions was observed for the determination of minocycline (MC), epitetracycline (ETC), tetracycline (TC) and doxycycline (DC). The manifold included a HPLC system with a photo-reactor (PTFE tubing helically coiled around a low-pressure mercury lamp), a mixing T-piece and a fluorescence detector. The derivatization reagent was delivered at 0.5 mL min −1 by a pump. After HPLC separation using a gradient system with a mobile ph…

Flow-injection analysis study of the chemiluminescent behaviour of proflavine and acriflavine

Abstract The chemiluminescent behaviour of the amino acridines like acriflavine, and proflavin is reported. Different strong oxidants (potassium permanganate, cerium(IV), hexacyanoferrate(III), hydrogen peroxide in different media) were tested, and potassium permanganate in sulphuric acid medium was selected. The study of the experimental parameters affecting the oxidation and detection was performed with the aid of a FIA assembly. The calibration graph was applied over the range 0.05–12.0 μg ml −1 of acriflavine (regression coefficient 0.9957, and the calculated relative standard deviation (R.S.D., %) was 0.9; LOD 10 ng ml −1 and the sample throughput 48 h −1 . The study of interfering com…

Cerium(IV) arsenite as a solid-phase reactor for use in flow-injection analysis. Spectrophotometric determination of promethazine

Abstract Cerium(IV) arsenite is used as a strongly oxidizing solid-phase reactor in an unsegmented continuous-flow injection assembly. Its preparation procedure produces particles of uniform size with suitable physico-chemical properties for use in a continuous-flow system. A manifold is proposed for the determination of promethazine in pharmaceutical preparations by spectrophotometric monitoring of the red colour produced by the oxidized drug. A linear calibration graph is obtained over the range 5–400 μg ml −1 of promethazine.

Determination of cyanide by a flow injection analysis-atomic absorption spectrometric method

A new flow injection analysis (FIA) procedure is proposed for the indirect atomic absorption spectrometric determination of cyanide. The FIA manifold is based on the insertion of the sample into a distilled water carrier, then the sample flows through a solid-phase reactor filled with silver iodide entrapped in polymeric resin beads. The calibration graph is linear over the range 0.2-6.0 mg l-1 of cyanide (correlation coefficient 0.9974), the detection limit is 0.1 mg l-1, the sample throughput is 193 h-1 and the RSD is 0.8%. The method is simple, quick and more selective than other published FIA procedures. The reproducibility obtained by using different solid-phase reactors and solutions …

Multicommutation as a powerful new analytical tool

This review presents the state of the art of the emerging continuous-flow methodology based on solenoid valves. This uses flow networks to deliver sample and reagent solutions by controlling the time of flow through the ON/OFF modes of solenoid valves and takes advantage of existing flow injection analysis (FIA) or sequential injection analysis (SIA) device or manifold configurations. It allows one to insert a single plug of sample (or reagent) into the carrier or carrier-reagent stream, mimicking the approaches of FIA or SIA. In addition to the modes used in FIA and SIA, the methodology provides a different mode, based on delivery of a series of alternating sequential insertions of very sm…

Photochemical derivatization and fluorimetric determination of reserpine in a flow-injection assembly

Abstract The fluorimetric flow-injection determination of reserpine was achieved with the drug being derivatized on-line by photoreaction. PTFE tubing was helically coiled around a germicide lamp located between the injection valve and detector. Two analytical procedures are proposed using either dilute acetic acid or pure methanol as the carrier stream. The influence of foreign compounds was studied and the method was applied to the determination of reserpine in pharmaceutical formulations.

Copper carbonate as a solid-bed reactor for spectrophotometric determination of doxycycline and oxytetracycline in an unsegmented continuous flow assembly

The FIA-spectrophotometric determination of doxycycline was carried out by reaction of the drug with cupric ions entrapped in a polymeric material in a packed-bed reactor: the complex formed was then injected into a manifold with an alkaline solution as carrier. The developed colour was monitored at 395.0 nm. The method was applied to the determination of doxycycline in different pharmaceutical formulations. The calibration graph for doxycycline hyclate was linear over the range 10.0-80.0 mg ml-1 (n = 8) with a relative standard deviation of 1.4% (at 25 mg ml-1) and a sample throughput of 128 h-1. The proposed procedure was also applied to the determination of oxytetracycline in pharmaceuti…

Flow injection biamperometric determination of chloramphenicol and related nitro compounds by on-line chemical photodegradation

Abstract An unsegmented continuous-flow assembly for the determination of chloramphenicol is proposed. The determination is based on the on-line photodegradation of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor consisting of a 697 cm long × 0.8 mm ID piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol is detected by photolytic cleavage of nitrite from the parent compound as well as by organic oxidizing photofragments, and their subsequent reaction with iodide ion, which is monitored biamperometrically. Triiodide thus formed is detected in excess iodide solution by polarizing two platinum electrodes at 100 mV. The calibration…

Quantitative colorimetric analysis of some inorganic salts using digital photography

An analytical imaging approach to the quantitation of dissolved chemical species absorbed in the visible spectral region is reported. The approach uses digital images of a series of standard solutions of the target substance and their processing with appropriate software to assign a numeric value to each standard in terms of color intensity. Such a value is directly proportional to the analyte concentration and allows the construction of a calibration graph. The results thus obtained are compared with those provided by the classical spectrophotometricmethod used to run calibration curves for colored substances. The chemical imaging technique is relative simple and affordable; in fact, it ca…

Flow spectrophotometric determination of ammonium ion

Abstract A flow procedure is proposed for the determination of ammonium ion. The sample in basic medium is forced through a solid-phase reactor containing immobilized AgCl on polymeric pearl beads. The released Ag + , complexed with the ammonia, gives a blue ternary complex with the aid of bromopyrogallol red and 1,10-phenanthroline which is spectrophotometrically monitored at 636 nm. The calibration graph is linear over the range 1–20 μg ml −1 ammonium ion, detection limit ( s / n  = 3)  0.35 μg ml −1 and relative standard deviation (slope) 1.9 % ( n  = 7). The sample throughput is 48 h −1 . The influence of foreign compounds is studied and the procedure is applied to ammonium ion determi…

A Fully Automated Assembly Using Solenoid Valves for the Photodegradation and Chemiluminometric Determination of the Herbicide Chlorsulfuron

Abstract This paper presents a new photochemiluminescent system for the determination of chlorsulfuron in water samples. The light from a low‐pressure mercury lamp is used as a clean, reproducible, and inexpensive “reagent” for the derivation of the pesticide, performed in glycine buffer at pH 9.5. Then, the photo‐products from irradiation are oxidized by permanganate in sulfuric acid solution. The oxidation reaction was favored by using high temperatures. A comparative study and discussion about the use of polyphosphoric acid instead of sulfuric acid in the oxidation reaction is also presented. The use of solenoid valves allows for the easy, complete automation of the process with low samp…

Spectrophotometric determination of adrenaline with an oxidative column in a FIA assembly

Abstract A single channel FIA assembly is proposed for the spectrophotometric determination of adrenaline, the aqueous sample solution is directly injected into the carrier stream leading the sample through a manganese dioxide column at 80°C, and on to the spectrophotometer flow-cell. The calibration graph is linear up to 17 ppm of adrenaline. The influence of other substances has been studied and the method has been applied to the determination of adrenaline in a pharmaceutical formulation.

Simultaneous dissolution profiles of two drugs in pharmaceutical formulations by an FIA manifold

Abstract This article deals with the simultaneous determination of dissolution profiles of two drugs with overlapped spectra, present in the same pharmaceutical formulation. The official procedure for the dissolution profile is adapted to the continuous-flow methodology; the dissolution vessel is connected to an FIA manifold, in which the sample aliquots from the dissolution vessel are treated in order to adjust to the suitable pH and dilution degree to be monitored. The resulting solution is injected into the carrier stream, an acetic acid–acetate buffer at pH 4.3 and forced to the flow-cell of the spectrophotometer. The simultaneous determination of both profiles is based on the first der…

Automated Photo-Induced Fluorescence Determination of Flumetsulam

The present article deals with a new procedure for determination of the herbicide flumetsulam. The fluorimetric procedure is performed on the basis of photo-increased fluorimetric emission of the pesticide solution and by means of a multicommutation continuous-flow assembly. The alkaline solution containing the analyte is irradiated online and then directly forced through the fluorimeter flow cell. The analysis of different samples is completely automated, as the analyte separation was performed online by including a separation cartridge in the manifold. When dealing with solid samples (such as soil samples), the automation was completed by adding to the manifold the corresponding device fo…