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…

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.

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…

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.

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…

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 .

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…

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 …

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 …

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…

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 .

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.

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 …

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…

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).

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.

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…