Search results for "Detection limit"
showing 10 items of 810 documents
Derivatization of tertiary amphetamines with 9-fluorenylmethyl chloroformate for liquid chromatography: determination of N-methylephedrine.
2000
The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) was evaluated for the derivatization of tertiary amphetamines prior to liquid chromatographic analysis. Conditions for the derivatization were investigated, including the reaction time, the derivatization reagent concentration and the pH, using N-methylephedrine as a model compound. On the basis of these studies, a method for the quantification of N-methylephedrine is presented. The method involves derivatization with FMOC at ambient temperature and separation of the derivatives formed on a LiChrospher C18, 5 μm, 125 × 4 mm id column using acetonitrile–water gradient elution. The proposed procedure shows good linearity, accuracy…
Hard Cap Espresso Machine Extraction of Polyphenolic Compounds from Pulses
2018
A hard cap espresso machine was employed for the extraction of polyphenolic compounds from food samples as dry legumes and pulses. 100 mg of ground dry sample was mixed with a dispersing agent and placed in a refillable stainless steel capsule with a borosilicate filter. A complete polyphenol extraction was achieved by using 150 mL ethanol 50 % (v/v) in water and determined by Folin-Ciocalteu spectrophotometric method. The method provided a limit of detection of 0.4 mg g<sup>-1</sup>. The whole extraction procedure was achieved in less than one minute using the mild extraction conditions of 72°C and 19 bars given by the domestic machine. Fifteen varieties of food samples (3 lent…
Chemiluminometric determination of the pesticide 3-indolyl acetic acid by a flow injection analysis assembly
2005
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.
Determination of mercury in dry-fish samples by microwave digestion and flow injection analysis system cold vapor atomic absorption spectrometry
1997
Abstract Flow injection analysis system cold vapor atomic absorption spectrometry (FIAS-CV-AAS) preceded by a wet digestion in a microwave oven, as a method for measuring mercury in fish was studied. The digestion process and conditions of the FIAS (carrier concentration: HCl 3% v v ; reducing agent: SnCl2 2% w v : filling and injection times: 8 and 25 min, respectively; and sample volumes) were optimized. The analytical parameters of the proposed method (detection limit = 7.7 ng/g; precision intraassay = 6.7%; interassay = 14.0%) demonstrates its adequacy and are similar to the ones (detection limit = 19.4 ng/g; precision intraassay = 11.2%; interassay = 15.9%) obtained using a conventiona…
Flow injection Fourier transform infrared determination of caffeine in coffee
1999
Abstract A fully automatized procedure has been developed for the Fourier transform infrared (FT-IR) spectroscopic determination of caffeine in coffee samples. The method involves the on-line extraction of caffeine with CHCl3. Samples, weighed inside empty PTFE cartridges of 0.5 cm internal diameter (i.d.) and 1.5 ml volume, were humidified with four drops of 0.25 M NH3. The cartridge was installed in a flow manifold, in which samples were extracted in a closed-flow system with 1 ml CHCl3 during 6 min. Four hundred microliters of the extract were introduced in a microflow cell and absorbance measured as a function of time at 1659 cm−1, with a baseline established between 1900 and 830 cm−1, …
Flow injection determination of free and total cholesterol in animal greases using enzymes in non-aqueous media
1998
A non-covalently coimmobilized bienzymic reactor of horseradish peroxidase (HRP) and cholesterol oxidase (COD), operating in a continuous organic flowing stream of 1 × 10–3 M p-anisidine in buffer-saturated (pH 7.0) toluene, has been employed for cholesterol determination in animal greases, such as pig, beef, and chicken fat, and codfish liver oil. The method provides a good linear relationship up to 1.8 × 10–3 M cholesterol and average recoveries of 99.5%, a high sensitivity, with a detection limit of 1 × 10–6 M of cholesterol and a good precision (an interday RSD of 1.8% for the determination of total cholesterol in a codfish oil sample). The method permits the direct spectrophotometric d…
Flow injection-spectrophotometric determination of cresol compounds in water by reaction withp-aminophenol
1993
A spectrophotometric method has been developed for the simultaneous determination ofo-cresol andm-cresol in water by reaction withp-aminophenol (PAP). Three different methodologies have been assayed; (i) batch analysis, after reaction in an alkaline medium in the presence of dissolved molecular oxygen as oxidizing agent, (ii) a stopped-flow procedure, carried out in the presence of KIO4 and (iii) a flow injection method based on the same approach. The batch procedure requires 22 min for the full development of colour witho-cresol and 12 min form-cresol. In the stopped-flow mode, using KIO4 and a reaction time of 12 min, better sensitivity can be obtained for both compounds and limits of det…
A multicommuted flow system with solenoid micro-pumps for paraquat determination in natural waters.
2007
A flow system designed with solenoid micro-pumps is proposed for the determination of paraquat in natural waters. The procedure involves the reaction of paraquat with dehydroascorbic acid followed by spectrophotometric measurements. The proposed procedure minimizes the main drawbacks related to the standard chromatographic procedure and to flow analysis and manual methods with spectrophotometric detection based on the reaction with sodium dithionite, i.e. high solvent consumption and waste generation and low sampling rate for chromatography and high instability of the reagent in the spectrophotometric procedures. A home-made 10-cm optical-path flow cell was employed for improving sensitivit…
o-Dianisidine: a new reagent for selective spectrophotometric, flow injection determination of chlorine
2002
A flow injection analysis (FIA) procedure for the determination of free chlorine in industrial formulations and water samples is proposed. The manifold is provided with a gas-diffusion unit which permits the removal of interfering species and also the preconcentration of chlorine. The determination of chlorine is performed on the basis of the oxidation by o-dianisidine as a chromogenic reagent to a coloured product which can be monitored at 445 nm. The method (for a preconcentration step of 60 s) is linear over the range 0.04-1.00 mg l(-1) of chlorine, the limit of detection is 0.04 mg l(-1), the reproducibility of the procedure (as RSD of the slope) is 3.7% for a series of four independent…
Zwitterionic Sulfonates as m/z Shift Reagents for 5-Methylcytosine Detection in Deoxyribonucleic Acids (DNA) Using Flow Injection Analysis and Electr…
2015
5-Methylcytosine (5-MC) is an important epigenetic modification of DNA. Abnormally high concentrations of this substance appear because of the hypermethylation of cytosine. Therefore, the measurement of the quantity of this compound in mammals is of great importance. Recently, we reported that several imidazolium-based zwitterionic sulfonates form complexes with 5-MC in solution, which can be studied by electrospray ionisation mass spectrometry (ESI-MS). It is shown in this paper that such an association can be utilised for the detection of 5-MC in a DNA sample using high-throughput a flow injection analysis ESI-MS method. A variety of the sulfonate zwitterions have been tested as m/ z shi…