Determination of caprolactam by adsorptive voltammetry after separation by thin-layer chromatography

Caprolactam (2-oxohexamethyleneimine) can be determined in wastewaters and natural waters by adsorptive stripping voltammetry after separation of the product of the reaction between caprolactam and p-(N,N-dimethylamino)benzene-p′-azobenzoyl chloride. When a hanging mercury drop electrode is used with an accumulation time of 60 s in stirred solution, caprolactam can be determined from a lower limit of 0.2 μg ml^?1. With a 360-s accumulation time, linear calibration plots are obtained for 8 × 10^?10?8 × 10^?9 mol l^?1 caprolactam. The effect of interfering sample components is eliminated by the TLC separation.