Antony C. Calokerinos

Flow injection chemiluminometric determination of epinephrine, norepinephrine, dopamine and L-dopa

A method is proposed for the determination of 0.0500-1.00 microgram ml-1 of epinephrine and L-dopa and 0.100-1.00 micrograms ml-1 of norepinephrine and dopamine by their chemiluminogenic oxidation with potassium permanganate in acidic medium, in the presence of formaldehyde, which greatly improves the sensitivity. Flow injection allows the measurement of 80 solutions per hour. The method was also optimized for a continuous-flow system. Comparative results from numerous organic compounds proved the necessity for electron-donating groups on the benzene ring for sensitive chemiluminescent characteristics.

Chemiluminescence determination of captopril based on a Rhodamine B sensitized cerium(IV) method

Abstract A new Chemiluminescence method for the determination of captopril is described. The method is based on the Chemiluminescence reaction of captopril with cerium(IV) in sulphuric acid medium. Rhodamine B is suggested as a fluorescing compound for the energy-transferred excitation. This sensitized-type of Chemiluminescence emission allows quantitation of captopril concentrations in the 0.1–6.0 μM range with a detection limit of 0.037 μM original concentration. The experimental conditions for the reaction are optimized, the possible reaction mechanism is discussed and a direct application on a commercial drug formulation is given.

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.

Determination of quinine and quinidine by continuous-flow chemiluminescence

Abstract A rapid and precise continuous-flow method is described for the determination of quinine and quinidine (5.00–500 μg ml −1 ) which is based on the sensitizing effect of the compounds on the chemiluminescent oxidation of sulphite by cerium(IV). When applied to tablets, the procedure is relatively free from interferences from common excipients. The results obtained for the assay of commercial formulations compared well with those obtained by an official method and demonstrated good accuracy and precision.

Continuous-flow chemiluminometric determination of some tetracyclines

Abstract Chemiluminescene is found to be generated by the action of lucigenin or hexacyanoferrate(III) on tetracyclines. The reaction with lucigenin exhibits chemiluminescence after alkaline degradation of tetracyclines to the corresponding iso derivatives. The reaction with hexacyanoferrate(III) occurs after acidic degradation of tetracyclines to the corresponding anhydro derivatives. The chemiluminescence reaction takes place in alkaline medium, and allows the development of a continuous-flow method for the determination of 0.100–1.20 μg ml−1 tetracycline, 0.100–10.0 μg ml–1 chlortetracycline and 1.00–10.0 μg ml−1 oxytetracycline and doxycycline. When applied to commercial formulations, the procedure was relatively free from interferences from common excipients. The results obtained for the assay of dosage forms compared well with those obtained by the official methods and demonstrated good accuracy and precision.

Chemiluminescence arising from the oxidation of bilirubin in aqueous media

Abstract Novel chemiluminogenic redox reactions of bilirubin in aqueous media are reported. N-bromosuccinimide and sodium hypochlorite were the oxidants which generated the most intense radiation and the corresponding reactions were monitored using a batch chemiluminometer. Consequently, the reaction of bilirubin with N-bromosuccinimide was further investigated using a flow injection analyser and the reaction, with hypochlorite, was further examined by using a continuous flow analyser in order to automate the procedure. The results indicate that both procedures are very sensitive (batch procedure with NaClO: linear range 0.2–20 μg ml−1; 3σ detection limit 50 ng ml−1) since bilirubin at concentrations less than 1 μg ml−1 can be easily and reproducibly measured. Albumin interferes seriously by enhancing the emission.

Determination of thiamine by continuous flow chemiluminescence measurement

The chemiluminescence produced by oxidation of thiamine by ferricyanide in alkaline medium has been investigated by using a simple continuous flow analyser and a procedure developed for the determination of thiamine hydrochloride or nitrate in the range 2.00 x 10(-5)-5.00 x 10(-4)M (equivalent to 6.75-169 mug/ml thiamine hydrochloride) with coefficients of variation <2%. A measurement rate of 112/hr can be obtained. When applied to pharmaceutical formulations, the only interferent among common excipients and coexisting drugs is ascorbic acid. The results obtained for the assay of dosage forms compared well with those obtained by an official method and demonstrated an error <4%.

Continuous-flow chemiluminescence determination of acetaminophen by reduction of cerium(IV)

A rapid and precise continuous-flow method is described for the determination of acetaminophen (1.00–10.0 µg ml–1) based on the chemiluminescence produced by its reaction with cerium(IV) in acidic solution. When applied to tablets, the method is relatively free from interferences from common excipients and co-existing drugs. The results obtained for the assay of commercial pharmaceutical preparations compared well with those obtained by a reference 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%).

Flow-injection chemiluminometric determination of sodium cyclamate

Abstract The sensitizing effect of sodium cyclamate on the chemiluminogenic oxidation of sulphite by cerium(IV) in sulphuric acid allows the determination of the artificial sweetener in the range 1.00–50.0 μg ml −1 . The flow-injection method developed is rapid and precise and allows measurements on up to 100 solutions per hour. Acetonitrile does not alter significantly the analytical characteristics of the method, which can therefore be proposed for the determination of the analyte after liquid chromatographic separation from other sweeteners and possible metabolites.