ABSTRACT
A simple, rapid and precise flow injection chemiluminescence (FI-CL) method is proposed for the determination of cefadroxil and is suitable for application to other antibiotics containing phenolic hydroxyl groups. A possible mechanism for this selectivity is suggested. The method is based on the CL-emitting reaction between cefadroxil and potassium permanganate in sulfuric acid medium, enhanced by formaldehyde (HCHO). Under the optimum conditions, calibration graphs over the ranges of 0.05-0.8 and 1.0-10.0 microg ml(-1) were obtained. The proposed method was successfully applied to the determination of cefadroxil in pharmaceutical formulations with no evidence of interference from common excipients. The detection limit (3sigma) of this method is 25 ng ml(-1) (6.9 x 10(-8) mol l(-1)). The relative standard deviation was less than 2% for 0.4 and 4.0 microg ml(-1) cefadroxil (n = 20). The sample throughput was found to be 120 h(-1).
Subject(s)
Anti-Bacterial Agents/analysis , Cefadroxil/analysis , Formaldehyde/chemistry , Pharmaceutical Preparations/analysis , Potassium Permanganate/chemistry , Calibration , Excipients , Flow Injection Analysis , Luminescent Measurements , Pharmaceutical Preparations/standards , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
A novel ultrasonic flow injection chemiluminescence (FI-CL) manifold for determining hydrogen peroxide (H2O2) has been designed and evaluated. Chemiluminescence obtained from the luminol-H2O2-cobalt(II) reaction was enhanced by applying 120 W of ultrasound for a period of 4 s to the reaction coil in the FI-CL system and this enhancement was verified by comparison with an identical manifold without ultrasound. The system was developed for determining ultra-trace levels of H2O2 and a calibration curve was obtained with a linear portion over the range of 10-200 nmol L(-1) H2O2 (correlation coefficient 0.9945). The detection limit (3sigma) and the quantification limit (LOQ) were found to be 1 x 10(-9) and 3.3 x 10(-9) mol L(-1) respectively and the relative standard deviation was 1.37% for 2 x 10(-7) mol L(-1) H2O2 (n = 10). The method was applied to the determination of trace amounts of H2O2 in purified water and natural water samples without any special pre-treatments.
ABSTRACT
Continuous monitoring can be used to detect rhythms, an important aspect of biology. But peaks of concentration are broadened by dispersion so that they overlap their neighbours and obscure high frequency chemoperiodicities. In this study, flow injection was found experimentally to be useful in resolving these. A rhythmically varying pattern of permanganate concentration was measured spectrophotometrically. The rhythm (frequency 0.08 Hz) was observable at a dispersion coefficient of 3.0 but not at 3.9 (when only a single peak was recorded). It was again observable using the same high dispersion manifold but positioned after an injection valve that subsampled the stream at intervals. A design based on this work is proposed for an automated instrument that outputs a time series of concentration measures.
