Characterisation of a transparent optical test strip for quantification of water hardness |
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Authors: | L.F Capitá n-Vallvey,M.D Ferná ndez-Ramos,F Santoyo-Gonzá lez |
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Affiliation: | a Department of Analytical Chemistry, Faculty of Science, University of Granada, Avda. Fuentenueva s/n, Granada 18071, Spain b Department of Organic Chemistry, University of Granada, Granada 18071, Spain |
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Abstract: | An optical and reversible test strip that uses an ion-exchange mechanism which responds equally to calcium and magnesium and makes it possible to determine water hardness is described. The transparent test strip, made of a polyester sheet, has a circular polymeric film of plasticised poly(vinyl chloride) (PVC) that contains all of the reagents necessary to produce an equal response to calcium and magnesium, namely, a cation-selective neutral ionophore, such as 4,13-[bis(N-adamantylcarbamoyl)acetyl]-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane, a chromoionophore, such as lipophilised Nile Blue, and potassium tetrakis (4-chlorophenyl)borate as a lipophilic salt, which it is evaluated by absorbance measurement at 655 nm in a standard photometer.All experimental variables that influence test strip response, especially in terms of selectivity and response time, have been studied. The sensor responded linearly to hardness up to 14,800 mg l−1, in activities, expressed as CaCO3. The detection limit is 1.9 mg l−1 as CaCO3, the reproducibility intermembrane at a medium level of the range was 7.0%, as R.S.D., of and 2.6% as intramembrane. The procedure was applied to the determination of hardness in different types of waters (tap, well, mineral and spring) validating results against a reference procedure. This proposed method is quick, inexpensive, selective and sensitive and uses only conventional instrumentation. |
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Keywords: | Hardness determination Optical test strip Ionophore-chromoionophore system Water analysis |
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