COMPUTERIZED PIPETTES WITH PROGRAMMABLE DISPENSION FOR BATCH INJECTION-ANALYSIS

New computer controlled pipettes are used to establish several dispension patterns and thus to enhance considerably the power of batch injection analysis (BIA). The unique delivery functions offered by these programmable pipettes permit advanced BIA operations with greater versatility and solution handling capability. Particularly attractive are the abilities to induce the dispersion (via prolonged or reversed sample dispensions), to inject simultaneously two (air-segmented) sample/standard solutions, to inject accurately extremely small samples (down to 0.5-mu-l) at different rates, or to perform acid-base titrations. Repetitive oscillations of the dispension greatly improve the contact of reactants, as illustrated for enzymatic reactions. High precision accrues from the highly reproducible (operated-independent) piston movement. Repetitive injections of 1-mu-l solutions are performed with a sample throughput of 300 per hour, with a relative standard deviation of 1.5%. The effect of these novel dispension patterns on the BIA response are evaluated using potentiometric and amperometric detection schemes. Prospects of using these pipettes in other automated analytical systems are discussed.