In the present investigation two modifications of the injection techni
que (flow and batch) for an Hg ion-selective electrode have been appli
ed. The optimal analytical parameters are found: sample volume, carrie
r flow rate, cell volume, tip-electrode distance, stirring rate. A lim
it of detection of 3x10(-7) mol l(-1) for a sample of mercury perchlor
ate of about 0.5 ml is obtained for the flow-injection analysis.