Determination of sulfate ion with 2-aminoperimidine hydrobromide using an optode based on tetrabromophenolphthalein ethyl ester membrane

An optode method for the determination of sulfate ion was developed. The optode membrane is 2-nitrophenyl octyl etherplasticized poly(vinyl chloride) membrane containing tetrabromophenolphthalein ethyl ester. The method is based on formation of an ion associate between the excess of 2-aminoperimidine hydrobromide (Ap) and sulfate ion in the sample solution, and detection of the concentration of the remaining Ap ion by the optode. Under the optimal conditions, a good linear relationship was found to exist between the absorbance of the optode membrane, and concentrations of sulfate ion in a concentration range from 20 to 400 μM. The developed optode method was applied to the determination of sulfate ion in environmental water samples.