Using a calcium electrode to measure mercury in aqueous solutions

Small specific-ion electrodes and computer signal processing have been developed, making it possible to measure the uptake or release of ions from concentrated cell suspensions by monitoring the changes in activity in the suspending solution. The effect of mercury chloride on calcium-selective electrode output was measured. A rapid and reversible depression of calcium electrode voltage by mercury was observed, showing that the electrode could be used to measure mercury concentrations. Mercury levels were determined in solutions of coelomocytes from Glycera dibranchata in seawater and of red blood cells from Raja erinacea and rectal gland cells from Squalus acanthias in elasmobranch Ringers solution. The calcium-selective electrode could be used to measure mercury concentrations of 10 uM to greater than 2 mM. Since the calibration curve is sensitive to calcium concentration, it is necessary that the calcium concentration in the solution is known and constant.