TUBULAR DETECTORS FOR FLOW-INJECTION POTENTIOMETRIC DETERMINATION OF TETRAFLUOROBORATE IN ELECTROPLATING BATHS

PVC tetrafluoroborate tubular electrodes without an inner reference so lution, based on tetraoctylammonium as the ion exchanger and 2-nitroph enyloctyl ether as the mediator solvent, were constructed. The general operating characteristics of the tubular detectors were evaluated by a single line flow-injection system with low sample dispersion and com pared to those of corresponding conventionally-shaped electrodes, dete rmined in batch conditions. In flow-injection analysis (FIA), the dete ctor response was linear in the concentration range between 4 X 10(-6) and 10(-1) M, with a mean slope of 59.2 +/- 0.9 mV/dec in the pH rang e between of 2.7 and 11.5. The reproducibility of the detector potenti als was approximately 0.2 mV during a day of continuous operation. The membrane used showed a high degree of selectivity. The tubular detect ors remained operational over a long period of time (approximately 36 months) and had a response time that enabled a sampling rate of 360 h( -1). The electrodes were later used in the determination of tetrafluor oborate in concentrated electrolytic baths for which a high dispersion FIA system was developed. The analyses of seven baths with different compositions presented results with mean recovery values of 98.8% with a coefficient variation of 1.9%.