Abstract
The interfacial and redox behavior of lorazepam at the hanging mercury drop electrode was studied by adsorptive stripping voltammetry. Both linear and differential pulse scan modes were used to record the stripping curves. A critical evaluation of adsorptive accumulation in stripping analysis in which differential pulse voltammetry was used for the measurement step is described. Generally applicable conditions for the method are 0.02 M Britton-Robinson buffer at pH 2.0 with a −0.39 V accumulation potential. The effect of various urine components on the voltammetric response was also studied, and preliminary separation of the drug was found necessary to avoid interference caused by albumin and uric acid. The applicability to human urine analysis is described. The detection limit was 15 ng lorazepam/ml urine (25 s accumulation time) and the mean standard deviation was lower than 3.1% for 316 ng ml −1 samples ( n = 5 and 25 s accumulation time), with a mean recovery of 99%.
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