On-line electrochemical reagent production for detection in liquid chromatography and continuous flow systems

The on-line electrochemical production of bromine as a reagent for detection in liquid chromatography is studied. For detection, the excess of bromine after reaction with an analyte in the column effluent is measured amperometrically. Phenolic ethers are used as model compounds. The relations between generating current, reaction time, rate constant, signal and noise are investigated. Rate constants were measured in batch experiments with rotating ring-disk electrodes. Lower and upper limits of detection are predicted. Under favourable conditions, detection limits are shown to be in the subnanogram range. The optimal generating current, with respect to sensitivity and selectivity, is discussed in detail. The determination of opiates (morphine, codeine, noscapine and papaverine) is used an example of the efficacy of the method.