Voltammetric studies of pinazepam and BrTDO accumulation at the HMDE surface

The interfacial and redox behaviour of pinazepam and BrTDO was studied at a hanging mercury drop electrode (HMDE). The results obtained suggested that electron transfer is preceded by adsorption; a Frumkin - type adsorption process was established for both compounds. The limiting value of the surface concentration indicates that the average surface occupied per adsorbed molecule is 2.80 and 3.15 nm2. Determination of pinazepam and BrTDO can be performed (down to the 10−9M level) by using adsorption as a preconcentration step prior to determination by differential pulse voltammetry in 0.04 M Britton-Robinson buffer at pH 4.0 and 5.0 with preconcentration potentials of −0.50 and −0.60 V, respectively. The detection limits were found to be 2.8 × 10−10M (6 min preconcentration) for pinazepam and 2.2 × 10−10M (8 min preconcentration) for BrTDO, and the relative standard deviation for 6.10 × 10−8M pinazepam (6 min) was 2.7% and for 8.2 × 10−8M BrTDO (8 min) 1.5%. Applicability to human serum analysis is illustrated.