Determination of sulfur-containing antibiotics using high-performance liquid chromatography with integrated pulsed amperometric detection

• Published in: Drug development research Vol. 53; no. 4; pp. 268 - 280
• Main Authors: Hanko, Valoran P., Lacourse, William R., Dasenbrock, Catherine O., Rohrer, Jeffrey S.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 01.08.2001; Wiley-Liss
• Subjects: amperometry; Analysis; Antibacterial agents; antibiotics; antibiotics, sulfur‐containing; Antibiotics. Antiinfectious agents. Antiparasitic agents; Biological and medical sciences; electrochemical detection; General pharmacology; high-performance liquid chromatography; HPLC; integrated pulsed amperometric detection; IPAD; Medical sciences; PAD; Pharmacology. Drug treatments; purity; stability; sulfur-containing; Electrochemical analysis; Cefradine; Chemical stability; β-Lactams; HPLC chromatography; Dissolution; Antibiotic; Cephalosporin derivatives; Analysis method; Reproducibility; Analytical method; Amperometry; Dosage form; Tablet; Antibacterial agent; Cefapirin; Sulfur; Physicochemical properties; Quantitative analysis
• ISSN: 0272-4391; 1098-2299
• DOI: 10.1002/ddr.1196

Sulfur‐containing antibiotics (e.g., ampicillin, penicillin, lincomycin, cephalosporin, and sulfanilamide) are a general class of compounds that have antibacterial properties. Some of these antibiotics lack a strong chromophore, and consequently are poorly detected using absorbance detection. The presence of oxidizable sulfur within an antibiotic’s molecular structure allows its direct detection by pulsed amperometry. Pulsed amperometry is an electrochemical detection method that uses a pulsed potential‐time waveform at a noble metal electrode surface to electrocatalytically oxidize analytes in proportion to concentration. The current for sulfur compounds on a gold (Au) electrode is caused by the desorption of the analyte previously adsorbed at the oxide‐free Au surface. Current integration in conjunction with rapidly changed voltage potentials is termed integrated pulsed amperometric detection (IPAD). Recent publications using high‐performance liquid chromatography (HPLC) with IPAD have demonstrated the capability to measure sulfur antibiotics. Our investigations of HPLC‐IPAD showed poor long‐term peak area reproducibility for these drugs. In this article, we present a new IPAD waveform that we demonstrate has good long‐term (>2 months) peak area reproducibility (4–5% relative s.d.). We show that a broad spectrum of sulfur‐antibiotic chemical structures can be detected, and we compare IPAD to absorbance detection. For nonchromophoric sulfur‐containing antibiotics, IPAD showed greater sensitivity than absorbance detection. The lower limits of detection, linearities, and peak area precision are compared for both IPAD and absorbance detection methods using seven antibiotics representing a diversity of chemical structures, including one nonsulfur‐containing antibiotic. The stabilities of cephradine and cephapirin were monitored using both IPAD and absorbance detections. Cephradine showed high chemical stability in aqueous ambient conditions at 10 μg/ml, whereas cephapirin showed a decomposition rate of 10% per day by both detection techniques. Some decomposition products could only be detected by IPAD. High recoveries were demonstrated for two antibiotics (sulfamethoxazole and trimethoprim) in a pharmaceutical tablet formulation. For the same formulation, the feasibility of conducting a dissolution study was also demonstrated. IPAD is a good primary detection method to complement or replace absorbance detection for nonchromophoric sulfur‐containing antibiotics and their sulfur‐containing impurities and decomposition products. HPLC‐IPAD is also a good confirming technique for sulfur antibiotics with chromophoric properties, and their impurities and decomposition products. Drug Dev. Res. 53:268–280, 2001. © 2001 Wiley‐Liss, Inc.