The reaction of vanadate with diphenylcarbazide
About: This article is published in Naturwissenschaften.The article was published on 1957-01-01. It has received 1 citation(s) till now. The article focuses on the topic(s): Diphenylcarbazide & Vanadate.
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TL;DR: The ITD separation was effective for matrix isolation and reduction of interferences, and potential cationic interferences were not transferred into the anionic Cr(VI) acceptor stream.
Abstract: Chromium speciation by spectrophotometric determination of hexavalent chromium (Cr(VI)) with diphenylcarbazide (DPC) has several problems. These include: (1) the inability to directly detect trivalent chromium (Cr(III)) with DPC, (2) positive interference in Cr(VI) determination by other metal cations and (3) negative interference by any reducing agent present in the sample. These are addressed with an ion transfer device (ITD) in a flow injection analysis system. We previously developed the ITD for electrodialytic separations. Here we separate oppositely charged Cr(III) and Cr(VI) species by the ITD into two different acceptor solutions within ~5 s. The acceptor solutions consist of buffered H2O2 to oxidize the Cr(III) to Cr(VI). Then DPC is added to either acceptor to measure Cr(III) and Cr(VI) spectrophotometrically. The system was optimized to provide the same response for Cr(VI) and Cr(III) with limits of detection (LODs, S/N=3) of 0.5 μg L-1 for each and a throughput rate of 30 samples h-1. The ITD separation was also effective for matrix isolation and reduction of interferences. Potential cationic interferences were not transferred into the anionic Cr(VI) acceptor stream. Much of the organic compounds in soil extracts were also eliminated as evidenced from standard addition and recovery studies.
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...In the present study, we fully optimize the use of ITD based Cr speciation with DPC-based measurement, with special attention to matrix isolation and interference in Cr(VI) measurements by metal cations [25-28] and anions [29,30]....
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84 citations
TL;DR: The mechanism of the classical color reaction between chromate and carbazide has been studied in solution from various physico-chcmical points of view as discussed by the authors, which leads to the conclusion that tlie chromate-carbazidc reaction is a composite one involving preliminary oxidation followed subsequently by complex formation.
Abstract: The mechanism of the classical colour reaction between chromate and carbazide has been studied in solution from various physicochcmical points of view. It has been established from spectral identity that the same red-violet compound is produced in the 3 different reaction systems, chromate-carbazidc, chromate-carbazone and chromous-carbazonc. This leads to the conclusion that tlie chromate-carbazidc reaction is a composite one involving preliminary oxidation followed subsequently by complex formation. Moreover, the actual constituents involved in the reaction have been identified as Cr +2 on the one hand and carbazone on the other, giving rise to an intensely coloured inner complex compound. The inner complex nature of the coloured product was gauged independently from migration studies and from extraction of the coloured compound by non-polar solvents.
37 citations