Optimization of a bipotentiometric flow injection analysis system for simultaneous determination of calcium and chloride ions in natural waters

Abstract

The experimental optimization by the modified simplex method of a bipotentiometric flow injection analysis (FIA) system, constituted by two different ion selective electrodes (ISEs) placed in series, for the simultaneous determination of calcium and chloride in waters is reported. The response function used was a weighted linear combination of three variables, chosen to achieve maximization of the calcium electrode sensitivity, minimization of the interference of the calcium signal on the chloride response and maximization of the sampling rate. The optimized system is able to determine calcium in the range 5 3 10 25 -5 3 10 23 mol l 21 with a sensitivity of ca. 27 mV decade 21 and chloride in the range 2 3 10 24 -2 3 10 22 mol l 21 , the maximum value tested, with a sensitivity of ca. 55 mV decade 21 . The repeatability found was 1.9 and 0.6%, respectively, at 2 3 10 24 and 2.2 3 10 23 mol l 21 (8 and 90 mg l 21 ), for calcium determinations, and 1.8 and 1.2%, respectively, at 3.4 3 10 24 and 8.3 3 10 24 mol l 21 (12 and 29 mg l 21 ), for chloride determinations. A sampling rate of 40 h 21 was obtained. The influence of the ionic strength on the results is discussed. The relative accuracy of the bipotentiometric FIA system was demonstrated by determination of the contents of both ions in natural waters in parallel with ASTM certified methods.

Electro‐driven extraction of inorganic anions from water samples and water miscible organic solvents and analysis by ion chromatography

“…The measurement of trace anionic contaminants in pure water samples is critical to the success of industrial processes such as semiconductor production and power plant operation . There are several methods reported in the literature for determination of inorganic anions, including spectrophotometry , ion selective electrode analysis , flow injection analysis , and CE . Ion chromatography (IC) is an effective analytical method with higher sensitivity for simultaneous determination of anions .…”

Continuous and simultaneous determination of anions and cations in rainwater by ion chromatography

“…There are many methods for determining these ions, such as spectrophotometry, 1,2 ion-selective electrode analysis, 3,4 atomic absorption spectrometry, 5 atomic emission spectrometry, 6,7 oscillopolarographic titration, 8,9 capillary electrophoresis, 10,11 flow injection analysis 12 and chemiluminescence analysis. 13 However, most of these methods cannot determine anions and cations simultaneously.…”