Highly sensitive semi-quantitative field test for the determination of chromium (VI) in aqueous samples |
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Authors: | Wolfgang Frenzel |
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Institution: | (1) Institut für Technischen Umweltschutz, Fachgebiet Luftreinhaltung, Technische Universit?t Berlin, Strasse des 17. Juni 135, D-10 623 Berlin, Germany e-mail: Luftrein@itu101.ut.TU-Berlin.DE, DE |
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Abstract: | A method for the semi-quantitative colorimetric determination of chromium(VI) at sub μg/L levels after sorptive preconcentration
is presented. The method is based on the retention of the reaction product (preformed in liquid phase) between Cr(VI) and
diphenylcarbazide on membrane embedded cation exchange material. The color intensity of the membrane can be correlated to
Cr(VI) concentrations in the range 0.05–50 μg/L (i.e. almost three orders of magnitude lower than the conventional spectrophotometric
procedure) with a detection limit of about 10 ng/L (using 50 mL of sample volume). Due to the visual inspection mode and comparative
color detection the precision is only 30–80% rsd which, however, is regarded as sufficient for screening purposes. Analysis
of real samples including different kinds of waters and extracts of soil and filter collected airborne particulate matter
demonstrated the applicability of the method for fast and species selective screening. Recovery experiments generally gave
reasonably good results, yet also revealed the risk of the conversion of chromium species during sample pretreatment procedures
due to redox reactions.
Received: 1 December 1997 / Revised: 23 February 1998 / Accepted: 10 March 1998 |
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