BATCH INJECTION WITH POTENTIOMETRIC DETECTION

The characteristics and advantages of employing ion-selective electrodes (ISEs) as detectors for batch injection (BI) systems are evaluated. Sharp potential response peaks are obtained for the injection of microliter samples onto the nearby ISE surface. Such dynamic measurements performed in batch systems result in high sample throughput and reproducibility, similar to those of established flow-injection operations. For example, pH measurements can be performed at rates of up to 720 samples per hour. There is no observable carry-over (between samples of low and high concentrations) and the precision is typically 1-2% (relative standard deviations). The applicability of BI-ISE system to chloride and fluoride measurements and for assays of real samples is also illustrated. The effects of various experimental variables on the BI potentiometric response are described. Such use of highly specific detectors offers many prospects for future use of BIA systems. The absence of pumps, injection valves and flow cells greatly reduces the instrumentation costs for rapid automated measurements of discrete ions.