Simultaneous multiple injection to perform titration and standard additionin monosegmented flow analysis

An automated system to perform titration and standard addition in monosegem ented flow analysis by employing the simultaneous multiple injection is des cribed. The system was controlled by a PC-AT-386 microcomputer through a ho me-made parallel interface, employing a diode array spectrophotometer as de tector. Software was written in QuickBasic 4.5 to control the system and fo r data acquisition. A three-way solenoid valve was used in conjunction with a proportional injector to add the titrant solution or the standard soluti on to the sample, to carry out titration or standard addition, respectively . Only one standard solution was used in each procedure and different quant ities of titrant or standard were added to the sample by controlling the ti me interval in which the solenoid valve was switched on. Titration and stan dard addition curves similar to those of the manual methods were obtained i n both cases, since the sample dispersion was very low due to the air bubbl es of the monosegment. The titration system was evaluated through the deter mination of Fe( II) with a KMnO4 standard solution in pharmaceutical prepar ations. The standard addition process was assessed by determining Cr( VI) i n natural waters and domestic wastewater using the diphenylcarbazide method . The results obtained in both methodologies did not differ significantly f rom the reference methods at a 95% confidence level.