Flow injection biamperometric determination of chloramphenicol and related nitro compounds by on-line chemical photodegradation

An unsegmented continuous-flow assembly for the determination of chloramphenicol is proposed. The determination is based on the on-line photodegradation of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor consisting of a 697 cm long x 0.8 mm ID piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol is detected by photolytic cleavage of nitrite from the:parent compound as well as by organic oxidizing photofragments, and their subsequent reaction with iodide ion, which is monitored biamperometrically. Triiodide thus formed is detected in excess iodide solution by polarizing two platinum electrodes at 100 mV. The calibration graph is linear up to 8 mg l(-1) chloramphenicol; the Limit of detection is 0.05 mg l(-1), the relative standard deviation is 0.4% (for 25 replicates of 10 mg l(-1) drug) and the throughput 68 samples h(-1). The proposed method was used to determine chloramphenicol in commercially available pharmaceutical formulations and human urine. (C)2000 Elsevier Science B.V. All rights reserved.