Improved detection limits and sensitivities of potentiometric titrations.
Zero-current ion fluxes through polymer membranes of ion-selective electrodes (ISEs) may lead to biased endpoints of potentiometric titrations. The bias is eliminated, and the sensitivity of the end-point detection is improved through reducing transmembrane ion fluxes by an appropriate choice of the inner solution. Surprisingly, ISE membranes that have a significant primary ion flux toward the inner solution show much larger sensitivities than expected by titration theory; however, depending on the experimental conditions, their application may bias the endpoint. With the optimal systems, endpoint detection is now possible with total sample concentrations below 10(-6) M, as demonstrated by the titration of EDTA with a Pb2+ solution.
Peper
S
S
Department of Chemistry, Auburn University, Alabama 36849, USA.
Ceresa
A
A
Bakker
E
E
Pretsch
E
E
D004492:Edetic Acid / Q000032:analysis; D023381:Endpoint Determination; D017736:Ion-Selective Electrodes; D007854:Lead / Q000032:analysis; D009566:Nitrates / Q000032:analysis; D011199:Potentiometry / Q000379:methods; D012680:Sensitivity and Specificity
D009566:Nitrates; D007854:Lead; C017461:lead nitrate; D004492:Edetic Acid