Meropi M. Timotheou-Potamia

Continuous-flow chemiluminescence determination of isoniazid by oxidation with N-bromosuccinimide

A rapid and precise continuous-flow method is described for the determination of isoniazid (0.050-20.0 micrograms ml(-1)) based on the chemiluminescence produced during its reaction with N-bromosuccinimide in alkaline medium. The emission intensity is greatly enhanced by the presence of ammonia. The procedure is automated and samples can be analysed at a rate of 112 solutions per hour with a relative error of about 2%. When applied to tablets, the method is relatively free from interferences from common excipients and co-existing compounds. The results obtained for the assay of commercial preparations compared well with those obtained by an official chemical method and demonstrated good accuracy and precision.

Continuous-flow chemiluminometric determination of tetracyclines in pharmaceutical preparations and honey by oxidation with N-bromosuccinimide

A continuous flow chemiluminometric method for determining 0.050-3.00 micrograms cm-3 of tetracycline, 0.50-5.00 micrograms cm-3 of oxytetracycline, 0.50-7.00 micrograms cm-3 of doxycycline and chlorotetracycline and 0.30-3.00 micrograms cm-3 of demeclocycline in pharmaceutical preparations and honey is described. The method is based on the chemiluminescence produced by the action of N-bromosuccinimide on tetracyclines in alkaline solution. The emission intensity is greatly enhanced by the presence of ammonia. The procedure is automated and solutions can be analysed at a rate of 130 h-1 with a relative error of about 2%. During evaluation of possible interferences of the method, recoveries from solutions with common excipients and other concomitant compounds were in the ranges 97.8-104.0 and 96.6-109.4%, respectively. Recoveries of various tetracyclines from commerical formulations and honey samples were in the ranges 95.2-103.7 and 89.2-106.6%, respectively. The results obtained for the assay of commerical pharmaceutical preparations compared well with those obtained by an official method and demonstrated accuracy and precision (< or = 5%).

Continuous-flow chemiluminometric determination of dihydralazine, rifampicin and rifamycin SV by oxidation with N-bromosuccinimide

Abstract A continuous-flow chemiluminometric method for the determination of dihydralazine sulphate (2.00–30.0 μg ml −1 ), rifampicin (0.0200–1.00 μg ml −1 ) and rifamycin SV (0.00500–1.00 μg ml −1 ) is described. The solutions are allowed to stand for about 4 h in alkaline solution before measurement in order to degrade to chemiluminogenic products. The method is based on the chemiluminescence produced during oxidation of these products by N -bromosuccinimide in alkaline medium. The emission intensity is greatly enhanced by the presence of ammonia. The procedure is automated and solutions can be analysed at a rate of 105 h −1 with a relative error of 1–3%. The method was evaluated by carrying out an interference study with common excipients and other co-existing compounds, by a recovery study and by the analysis of commercial formulations. The results obtained compared well with those obtained by an official method and demonstrated good accuracy and precision.

Kinetic-Potentiometric determination of ascorbic acid, biotin, pyridoxine hydrochloride and thiamine hydrochloride with N-bromosuccinimide

Abstract A kinetic-potenitometric method is proposed for the determination of ascorbic acid, biotin, pyridoxine hydrochloride and thiamine hydrochloride. The vitamin reacts with N -bromosuccinimide and the rate of production of bromide is monitored with a bromide-selective electrode. The method is simple, reliable and relatively free from interferences from common excipients and coexisting vitamins when applied to tablets and injections. The results obtained for the assay of commercial pharmaceutical preparations compare well with those obtained by official chemical methods and demonstrate good accuracy and precision.

Flow-Based Methods with Chemiluminescence Detection for Food and Environmental Analysis: A Review

This paper presents an overview of flow-based methods in food and environmental analysis using chemiluminescence (CL) detection covering the period from 2005 to the present. The review discussses both automated flow methods of analysis [such as flow-injection analysis (FIA), sequential-injection analysis (SIA) and their variants] and separation techniques [liquid chromatography (LC) and capillary electrophoresis (CE) coupled to CL detection]. The most widely used CL reactions are presented together with representative applications in food and environmental analysis (determination of naturally occurring compounds, contaminants, additives as well as determination of inorganic and organic compounds).

Continuous-flow chemiluminometric determination of ammonium ion in fertilizers.

A simple continuous-flow chemiluminometric method for the determination of 0.0540-5.40 mug/ml of ammonium ion is described. The method is based on the chemiluminescence generated during the oxidation of ammonium ion by N-bromosuccinimide in alkaline medium. The emission intensity is greatly enhanced if dichlorofluorescein is also present in the reaction solution. The analysis is automated, requires no sample pre-treatment and solutions can be analysed at a rate of 106 solutions/hr with a relative error of about 2.5%. The method was applied satisfactorily to the determination of ammonium ion in solid and liquid fertilizers.

Chemiluminometric determination of vanillin in commercial vanillin products.

Vanillin, ethylvanillin and 4-hydroxy-3-methoxy-benzylalcohol have been found to chemiluminesce by the action of potassium permanganate in sulphuric or polyphosphoric acid media. Both acid media have been compared and sulphuric acid allows the sensitive determination of 0.15-10.0, 0.010-1.0 and 0.0030-0.30microg mL(-1) of vanillin, ethylvanillin and 4-hydroxy-3-methoxy-benzylalcohol with limits of detection equal to 0.045, 0.0030 and 0.00090microg mL(-1), respectively. Recoveries of vanillin from commercial vanillin products are within the range of 95-109%. Comparison with results from the official method shows differences within the range of 0.5-3.0%. The chemiluminogenic reaction mechanism is also discussed.

Catalytic/kinetic potentiometric determination of organic iodine-containing compounds

Abstract A kinetic method is described for the determination of microgram amounts of various organic iodine-containing compounds, based on their catalytic effect on the cerium(IV)/arsenic(III) reaction. The time required for a 15-mV change in potential is inversely proportional to the compound concentration.

Chemiluminometric and Fluorimetric Determination of Folic Acid

Abstract Folic acid was found to inhibit the chemiluminogenic reaction of N‐bromosuccinimide with dichlorofluorescein in alkaline medium. The analyte has also been determined after generation of a fluorescing compound by the action of hexacyanoferrate(III) or N‐bromosuccinimide in alkaline medium. Both procedures were further investigated and an attempt to propose the corresponding mechanisms was also made. The chemiluminogenic procedure allows the determination of folic acid within the range 6.0 to 114 µg/ml with limits of detection and quantification equal to 2.0 and 6.0 µg/ml, respectively and rsd at 11.4 µg/ml equal to 1.0% (n=12) while the fluorogenic procedure allows the determination of folic acid within the range 0.022–1.10 µg/ml with limits of detection and quantification equal to 0.002 and 0.005 µg/ml, respectively and rsd at 0.022 µg/ml equal to 0.7 (n=10). The methods are compared and successfully applied to commercial preparations containing folic acid.

Kinetic study of N-bromosuccinimide reactions and kinetic determination of pyridoxine using a bromide-selective electrode

The bromide released by the alkaline hydrolysis of N-bromosuccinimide and its reactions with bromide, pyridoxine and thiamine have been studied potentiometrically using a solid-state bromide-selective electrode to monitor the consumed or produced bromide ion. Potential-time indications are obtained using a microcomputer-controlled potentiometric system. The overall rate constants and the activation energies have been calculated. A kinetic-potentiometric procedure for the determination of pyridoxine in the presence of thiamine in pharmaceutical preparations, based on its reaction with N-bromosuccinimide, is presented.