Simplex and classical methods for the selection of parameters for the adsorptive stripping voltammetric determination of nitralin. A comparative study

A method for the determination of the herbicide nitralin by adsorptive stripping voltammetry (AdSV) is proposed. This very sensitive method is based on controlled adsorptive preconcentration of the herbicide on a hanging mercury drop electrode (HMDE). Measurements were taken by differential pulse polarography (DPP) after improving with simplex method accumulation conditions, which was compared with those obtained by the classical methods of variable optimization. Using the simplex method means that the sensitivity is significantly increased compared to the sensitivity obtained by the conventional method (slope ratio 3.79). The time and the experiment number are smaller. Using this method the detection limit reached was 0.13 ng ml^-1. Under these conditions the peak current is enhanced 5-fold for 6 × 10^-9 M nitralin solution compared to the peak current from the classical method. The response was linear in the range 5 × 10^-10 to 1 × 10^-6 M, with two different slopes, and the coefficient of variation for a 5 × 10^-8 M nitralin solution (n = 10) was 0.90%.