Chlormequat Selective Electrodes: Construction, Evaluation and Application at Fia Systems

Abstract

A flow injection analysis (FIA) system having a chlormequat selective electrode is proposed. Several electrodes with poly(vinyl chloride) based membranes were constructed for this purpose. Comparative character-ization suggested the use of membrane with chlormequat tetraphenylborate and dibutylphthalate. On a single-line FIA set-up, operating with 1 x 10 -2 mol L -1 ionic strength and 6.3 pH, calibration curves presented slopes of 53.6 ± 0.4 mV decade -1 within 5.0 x 10 -6 and 1.0 x 10 -3 mol L -1, and squared correlation coeffi-cients > 0.9953. The detection limit was 2.2 x 10 -6 mol L -1 and the repeatability equal to ±0.68 mV (0.7%). A dual-channel FIA manifold was therefore constructed, enabling automatic attainment of previous ionic strength and pH conditions and thus eliminating sample preparation steps. Slopes of 45.5 ± 0.2 mV dec-ade -1 along a concentration range of 8.0 x 10 -6 to 1.0 x 10 -3 mol L -1 with a repeatability ±0.4 mV (0.69%) were obtained. Analyses of real samples were performed, and recovery gave results ranging from 96.6 to 101.1%.