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

An unsegmented continuous-flow assembly for the determination of chloramphe nicol is proposed. The determination is based on the on-line photodegradati on of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor con sisting 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 orga nic 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% (fo r 25 replicates of 10 mg l(-1) drug) and the throughput 68 samples h(-1). T he proposed method was used to determine chloramphenicol in commercially av ailable pharmaceutical formulations and human urine. (C)2000 Elsevier Scien ce B.V. All rights reserved.