HPLC online reductive scanning voltammetric detection of diquat, paraquat and difenzoquat with mercury electrodes

To establish an electrochemical HPLC detection system which is suitable for the voltammetric characterisation of unknown contaminants and food compone nts at working potentials lower than -1 V, a modified flow-through cell for the use of a hanging mercury drop electrode (HMDE) is described. The intro duction of silanised glass capillaries and a new flow-channel design provid e a high HMDE lifetime, which is recommended in HPLC detection. As test sys tem the herbicides diquat, paraquat and difenzoquat and ethylviologen as in ternal standard were measured using differential pulse voltammetry (DPV) de tection to improve selectivity. Spiked water samples were analysed with vol tammetric and UV-detection and results agreed well.