X. R. Zhang

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.

Chemiluminescence flow-injection analysis of captopril applying a sensitized rhodamine 6G method☆

A flow-injection analysis with chemiluminescence detection is described for the determination of captopril based on the photochemical reaction with cerium(IV) in sulphuric acid medium yielding a strong chemiluminescent signal which can be sensitized by some fluorescers. The proposed procedure has a linear application range of 1 x 10(-6) - 2 x 10(-4) M (r = 0.997) with a detection limit of 2 x 10(-7) M, an RSD of 2.8% at 1 x 10(-6) M captopril, and a sample measurement frequency of 500 h-1. The method was used for the simple and rapid determination of captopril in a pharmaceutical preparation.

Arsenic speciation in serum of uraemic patients based on liquid chromatography with hydride generation atomic absorption spectrometry and on-line UV photo-oxidation digestion

Abstract An on-line method was developed for the speciation of arsenic species in human serum, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB) and arsenocholine (AsC). The method is based on cation-exchange liquid chromatography (LC) separation, UV-photo-oxidation for sample digestion and continuous hydride generation (HG) atomic absorption spectrometry (AAS) for the measurement of arsenic in the LC eluent. By developing the technique of argon segmented flow in the post-column eluent, an substantial improvement in Chromatographic resolution for the separation of these four arsenic species was obtained. The LC separation, photo-oxidation, hydride generation and AAS measurement could be completed on-line within 10 min. The detection limits were 1.0, 1.3, 1.5 and 1.4 μg/l of arsenic for MMA, DMA, AsB and AsC, in serum respectively. The concentration of the 4 species was determined in serum samples of patients with chronic renal insufficiency. Only AsB and DMA were significantly detected by the present method. The main part of arsenic in human serum is AsB. No MMA, AsC and inorganic arsenic were detected in these 6 samples.

Chemiluminescence determination of some local anaesthetics

Abstract The analytical possibilities of the Chemiluminescence observed from some local anaesthetics on acidic permanganate treatment are investigated. Five drugs belonging to the p-aminobenzoate series gave significant emission and the reagent concentrations for their determination were optimized. The following detection limits were obtained: benzocaine, 30 ng ml−1; butacaine, 20 ng ml−1; butoform, 30 ng ml−1; procaine, 40 ng ml−1 and tetracaine 3 ng ml−1. The application of the reaction to the analysis of some pharmaceutical preparations containing benzocaine and procaine was evaluated.

Chemiluminescence determination of penicillamine via flow injection applying a Quinine–cerium(IV) system

A rapid flow injection method with chemiluminescence detection is described for the determination of penicillamine. The method is based on the chemiluminescence reaction of thiol-containing drugs with cerium(IV) in sulfuric acid medium. Quinine is suggested as a fluorescer for the energy-transferred excitation process. The optimum conditions for chemiluminescence emission were investigated. With peak height as a quantitative parameter, penicillamine can be determined over the concentration range 2–200 µmol l–1 with a detection limit of 15 pmol of original thiol. The method was applied to the determination of penicillamine in a pharmaceutical tablet preparation.

Chemiluminescence determination of tetracyclines based on their reaction with hydrogen peroxide catalysed by the copper ion

A flow injection-based method for the determination of tetracycline, chlortetracycline and oxytetracycline has been proposed. It is based on the reaction of the tetracyclines with hydrogen peroxide, catalysed by the copper ion in ammonia medium. Persulfate was used as a co-oxidizing agent. The procedure allows the determination of 0.025–2.5 nmol of chlortetracycline and 0.25–25 nmol of tetracycline and oxytetracycline (50 µl per injection) by the flow-injection method compared with 0.005–50 µmol l–1 of chlortetracycline and 0.05–500 µmol l–1 of tetracycline and oxytetracycline by the classical batch method. The method is sensitive, selective and easy to operate and can be used for the determination of tetracyclines in pharmaceutical preparations. A discussion on the possible reaction mechanism is presented.

Chemiluminescence detection coupled to liquid chromatography for the determination of penicillamine in human urine

Abstract An on-line liquid chromatography (LC) chemiluminescence detection system is proposed for the determination of penicillamine in human urine. Ion-pair reversed-phase LC using octane sulphonic acid as ion-pairing reagent allows the separation of penicillamine from the urine matrix. The Chemiluminescence reaction of penicillamine with Ce(IV) in sulphuric acid sensitized by quinine is suggested for sensitive penicillamine detection in a post-column mixing set-up. The Chemiluminescence response was linearly related to the concentration of penicillamine in the range 2.0–2000 μmol 1−1 (r = 0.9994, peak height, and 0.9997 peak area, n = 10) with a detection limit ( S N = 3) of 1.0 μ mol 1 −1 (100 pmol per injection). Relative standard deviations were less than 5% (n = 10) for 10–50 μmol 1−1. The excretion rates of penicillamine in human urine of three volunteers after oral penicillamine administration were determined in the present study.

Chemiluminescence determination of tiopronin and its metabolite 2-mercaptopropionic acid in human urine by HPLC coupled with flow injection

SummaryIn previous pharmacokinetic studies tiopronin, a drug used for effective treatment of cystinuria and rheumatoid arthritis, and its metabolite 2-mercaptopropionic acid were analysed by conventional liquid chromatography with pre- and post-column derivatization and UV detection. Now a novel HPLC-coupled chemiluminescence-flow-injection analysis (CL-FIA) method has been developed for the determination of tiopronin and 2-mercaptopropionic acid in urine. The method is based on chemiluminescence from a Ce(IV) oxidation system sensitized by quinine, as proposed earlier by this group, and flow-injection analysis. The method, which has the advantages of high sensitivity and selectivity, simple sample treatment and prompt production of results, has also been preliminarily adapted for pharmacokinetic study of tiopronin in urine.