Determination of mercury ion by MEKC with on-column derivatisation and LIF detection

A simple and automatic method for the determination of mercury ion by MEKC with on-column derivatisation and LIF detection is described in the present paper. In this method, solutions of a nonfluorescent rhodamine derivative and mercury ion were injected individually and mixed by applying a short voltage. Subsequently, the mercury ions reacted with the nonfluorescent rhodamine derivative to produce strongly fluorescent product. The resulting product was then removed by EOF and micelles towards the detection window and detected by LIF detector. The experimental conditions in terms of the concentration and injection volume ratios between mercury ion and derivatisation reagent, the mixing time and waiting time for the on-column reaction were optimised. The optimal conditions were determined as follows: the concentration and injection volume ratios between mercury ion and derivatisation reagent were 1:20 and 10:1, respectively; the mixing time was 40 s under the applied voltage of 5 kV; the waiting time was proved unnecessary. The detection limit for mercury ion was 5 x 10(-8) M, and the total analysis time was less than 10 min.