A test strip for chloride analysis in environmental water.
A disposable and reversible test strip for chloride is proposed. It is based on a polyester strip containing a circular sensing zone, 6 mm in diameter and 9.5 microm in thickness, with all the reagents necessary to produce a selective response to chloride. This sensing zone comprises a plasticized poly(vinyl chloride) (PVC) membrane that incorporates trioctyltin chloride as ionophore and 4',5'-dibromofluorescein octadecyl ester as chromoionophore. The prepared test strip works on a co-extraction system of chloride and hydrogen ions in the sensing zone. This disposable test strip can determine chloride simply by introducing the strip into a water sample containing a pH 2.0 buffer and measuring the absorbance at 534 nm as the analytical signal because the colour changes from red to orange. Experimental variables that influence the sensor response have been studied, especially those related to selectivity and response time. The sensor responds linearly in activities in the range 0.15-24.7 mM. The detection limit is 0.15 mM, the intermembrane reproducibility at a mid-level of the range is 6.4% relative standard deviation (RSD) of log aCl- and the intramembrane reproducibility is 4.5%. The procedure was applied to the determination of chloride in different types of water (tap, well, stream and sea), validating results against a reference procedure. This proposed test system for chloride determination in waters is inexpensive, selective and sensitive and uses only conventional instrumentation.
Department of Analytical Chemistry, University of Granada, Granada 18071, Spain. lcapitan@ugr.es
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Capitán-Vallvey
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Guerrero
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Merelo
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Ramos