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

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 characterization suggested the use of membrane with chlormequat tetraphenylborate and dibutylphthalate. On a single-line FIA set-up, operating with 1 2 10 m 2 mol L m 1 ionic strength and 6.3 pH, calibration curves presented slopes of 53.6 - 0.4 mV decade m 1 within 5.0 2 10 m 6 and 1.0 2 10 m 3 mol L m 1 , and squared correlation coefficients > 0.9953. The detection limit was 2.2 2 10 m 6 mol L m 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 decade m 1 along a concentration range of 8.0 2 10 m 6 to 1.0 2 10 m 3 mol L m 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%.