University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Dichromate

  • IUPAC Name: oxido-(oxido(dioxo)chromio)oxy-dioxochromium
  • Molecular Formula: Cr2O7-2
  • CAS Registry Number: NA
  • InChI: InChI=1S/2Cr.7O/q;;;;;;;2*-1
  • InChI Key: SOCTUWSJJQCPFX-UHFFFAOYSA-N

@ ChemSpider@ NIST@ PubChem

Citations 10

"Flow Injection Extraction-spectrophotometric Determination Of Dichromate With The Tetramethylenebis(triphenylphosphonium) Cation"
Anal. Chim. Acta 1989 Volume 225, Issue 1 Pages 241-246
D. Thorburn Burns, N. Chimpalee and M. Harriott

Abstract: Samples (0.25 ml) were injected into a stream (0.85 mL min-1) of water which was mixed with a stream (0.85 mL min-1) of 1 M H2SO4. This mixture was merged with a stream (0.85 mL min-1) of aqueous 0.5% tetramethylenebis(triphenylphosphonium) bromide in a PTFE reaction coil (20 cm x 0.8 mm), and the resulting ion pair was extracted into CHCl3 in a second PTFE coil (0.4 m x 0.8 mm). The mixture was passed through a phase separator, and the absorbance of the organic phase was measured at 365 nm. The calibration graph was rectilinear for 20 µg mL-1 of Cr2O72-, and the detection limit was 0.44 µg mL-1. The method was applied in the determination of Cr2O72- in steel.
Alloy Spectrophotometry Sample preparation Calibration Phase separator Ion pair extraction

"Sensitivity Enhancement By Potentiometric Flow Injection Analysis Based On Redox Reaction With An Iron(III) - Iron(II) Buffer"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 405-410
Nobuhiko Ishibashi, Toshihiko Imato*, Sumio Yamasaki and Hiroki Ohura

Abstract: For the determination of oxidizing species, the sample solution (200 µL) is injected into water as carrier and the stream is mixed with a reagent solution containing 0.01 M Fe(III) - 0.01 M Fe(II), 0.4 M NaBr and 1.2 M H2SO4 in a 100-cm reaction coil. The resulting solution passes to an oxidation - reduction potential electrode detector (cf. Ibid., 1988, 214, 349) for potentiometric measurement. The transient potential change is rectilinearly related to the concentration. of Cr2O72-, BrO3-, ClO2-, H2O2 or O3 (sensitivities tabulated). Detection limits for the first three species are 0.3 µM, 0.05 µM and 0.1 µM, respectively; the sensitivity towards H2O2 is enhanced by adding 0.5% of (NH4)6Mo7O24 to the reagent solution. A sampling rate of 40 h-1 is attainable. Highly sensitive potentiometric flow injection analysis for oxidative species such as bromate, chlorite, dichromate, hydrogen peroxide and ozone is described, using an Fe(III)-Fe(II) potential buffer containing bromide. The method is based on detection of large transient potential changes of an oxidation-reduction potential electrode which appear in short period after mixing a sample with the potential buffer. This large transient potential change is due to bromine generated by the reaction of the sample with bromide in the potential buffer. Anal. sensitivities obtained by the transient change of potential are enhanced 25-350-fold compared with that using the change in equilibrium. potential. Detection limits of 5 x 10^-8 M for bromate, 1 x 10^-7 M for chlorite and 3 x 10^-7 M for dichromate were obtained by using a 0.01 M Fe(III)-0.01 M Fe(II) potential buffer containing 0.4 M NaBr and 1.2 M H2SO4. For the determination of hydrogen peroxide, the addition of ammonium molybdate to the potential buffer accelerates the generation of bromine caused by the reaction of hydrogen peroxide with bromide and thus enhances the sensitivity.
Potentiometry Redox

"Pulse Coulometric Titration In Continuous-flow"
Analyst 1994 Volume 119, Issue 8 Pages 1835-1838
Anastas Dimitrov Dakashev and Veselina Todorova Dimitrova

Abstract: A suitable volume of a standard analyte solution or a solution of unknown analyte concentration was diluted to 25 mL with a reagent-generating solution containing 96.4 g of iron(III) ammonium sulfate, 112 mL of 96% H2SO4 and 87.5 mL of 85% H3PO4 per litre. The solution was passed continuously, at a constant flow rate, through a single-channel flow system consisting of consecutively joined generator and detector cells (diagram given). In the generator cell, the Fe(II) titrant was electrochemically generated in rectangular impulses of definite duration and different current magnitude. The analyte/titrant mixture then passed to the detector cell, and peaks were recorded corresponding to an excess of titrant generation, from which the concentration of the analyte was calculated (equation given). The described coulometric titration method was used to measure solution of K2Cr2O7, KMnO4, cerium(IV) sulfate and NH4VO3 from 0.1-10 milliequivalents/l, with RSD (n = 4-8) of 6.4-1.6%.
Coulometry Titrations

"Automation Of The Determination Of Hydrogen Peroxide, Dichromate, Formaldehyde And Bicarbonate In Milk By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1992 Volume 344, Issue 3 Pages 123-127
J. F. Cerdán, M. Peris-Tortajada, R. Puchades and A. Maquieira

Abstract: Automatic flow injection spectrophotometric methods for the determination of the preservatives, H2O2, dichromate, formaldehyde and bicarbonate in milk are described. The methods are based on reaction with vanadium pentoxide, diphenylcarbazide, fuchsine - SO2 and alizarin, respectively. Sample pre-treatment techniques suitable for online use, viz, dialysis and paper and membrane filtration, are discussed. Calibration ranges and coefficient of variations are tabulated for the four analytes. Recoveries were quantitative and sample throughput was 60 h-1. Automatic flow injection methods for the determination of H2O2, dichromate, formaldehyde, and bicarbonate in dairy products are based on reactions with V2O5, diphenylcarbazide, fuchsine-SO2, and alizarin, respectively. Sample pretreatment (paper and membrane filtration, dialysis) is discussed extensively for online incorporation. The usefulness of these methods was tested by applying them to different commercial samples, satisfactory results being obtained in all instances.
Cow Sample preparation Spectrophotometry Filtration Dialysis

"Capillary Batch Injection Analysis And Capillary Flow Injection Analysis With Electrochemical Detection. A Comparative Study Of Both Methods"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 2 Pages 189-193
U. Backofen, F.-M. Matysik, W. Hoffmann, H.-J. Ache

Abstract: Capillary batch injection analysis (CBIA) and capillary flow injection analysis (CFIA) in combination with electrochemical or optical detection methods were studied and compared with respect to their performance. Despite the differences in tech. equipment both techniques share the same idea of reliable transport and washout of nanoliter samples over sensing surfaces. The amperometric and potentiometric CBIA responses were studied under various experimental conditions in order to optimize the CBIA set-up. The dispersion of the sample solution relative to that of the cell electrolyte had a remarkable effect on the hydrodynamic characteristics of CBIA. Dispersion in CFIA was investigated using on column UV-detection for electroosmotic flow (EOF) conditions as well as for gravity flow conditions. For a 75 µm capillary the relative band broadening of the sample plug under gravity flow was twice as large as under EOF. Dispersion in a system that involves a chemical reaction between the sample and the carrier solution, namely CrO72- and Fe2+ was investigated by amperometric detection and exploited for the determination of microsamples.
Amperometry Potentiometry Spectrophotometry Electrophoresis Capillary Electroosmotic flow

"Indirect Determination Of Carbonate, Dichromate And Oxalate By Atomic Absorption Spectrometry In A Flow System Using An Online Preconcentration Technique"
Anal. Sci. 1994 Volume 10, Issue 4 Pages 687-690
F. T. ESMADI and A. S. ATTIYAT

Abstract: Standard solutions of dichromate, oxalate or carbonate and AgNO3 were passed through the flow system. The two solutions were mixed in the mixing coil (5 cm x 1 mm i.d.) and pumped to the precipitating loop where precipitation was allowed to occur for 2 min. The selecting valve first allowed a stream of washing solution of water to pass to the precipitating loop and then the dissolving solution was allowed to pass, dissolving the precipitate and carrying it to the nebulizer for analysis by AAS. Three dissolving agents were evaluated: NH3, HClO4 and H3PO4. The calibration graphs for the three anions were all within the range 0.01-0.22 mM with detection limits of 1-8 µM and RSD of 1-1.3% (details given). The effects of foreign ion are discussed.
Spectrophotometry Preconcentration Indirect

"High-speed Flow Injection Determinations Of Oxidative Agents In Aqueous-solutions Based On Reaction With An Online Generated Leuco Dye"
Chem. Tech. 1990 Volume 42, Issue 7 Pages 304-307
MUÊLLER H. ; HANSEN E. H.

Abstract: In a FIAstar 5020 automatic analyzer. (Tecator) with motor-driven injector loop (60 µL), streams (2 mL min-1) of aqueous thionine violet solution (0.2 mg mL-1) and of EDTA solution (3 g in 100 mL of water, diluted to 200 mL with acetate buffer of pH 4.7) were combined and passed through a glass reaction coil (1 m x 2 mm) under a 250-W high-pressure Hg lamp to reduce the dyestuff to its leuco form. Sample solution [e.g., Cr2O72-, Fe(CN)63-, VO3-, S2O82- or Fe3+] was injected into the stream, and the absorbance was measured at 600 nm in a Corning 252 flow-through photometer with a Hellma 178.012 QS flow-through cell (10 mm; 18 µL). Up to 180 samples h-1 can be analyzed. The limit of detection is ~1 µM. As H2O2 reacts only at concentration. of >10 to 100 mM, the determination of, e.g., 10 µM-S2O82- is possible in a 150-fold excess of H2O2.
Spectrophotometry Automation Tecator Injector EDTA Buffer pH Detection limit

"Direct Reading Of Signals Obtained In Flow Injection Analysis"
Quim. Nova 1982 Volume 5, Issue 2 Pages 51-53
Pasquini, C.;De Oliveira, W.A.;Pasquini, C.

Abstract: A method is described for the direct reading of signals obtained in flow injection analysis which did not depend on the use of a microprocessor but was of simple low-cost construction. Experiments were made with K2Cr2O7 solutions in which routine absorption readings were made at 372 nm with a spectrophotometer, and 240 signals could be obtained per h.
Spectrophotometry Apparatus

"Redox Reactions In Potentiometric Continuous-flow Analysis"
J. Anal. Chem. 1996 Volume 51, Issue 9 Pages 851-854
N. V. Sorokina, Yu. I. Urusov, and O. M. Petrukhin

Abstract: The concentration of H2O2 was determined by the continuous-flow method with a Ag2S/AgI fluoride ISE as a detector and 0.5 M ferrous ammonium sulfate and 0.55 M NaF as the supporting redox electrolyte. Up to 600 samples/h could be analyzed with RSD values depending on the rate of analysis. An analogous method was used for the determination of dichromate and permanganate.
Potentiometry Redox

"Microprocessor-based Instrument For Flow Injection Analysis"
Zhongguo Yaoke Daxue Xuebao 1991 Volume 22, Issue 1 Pages 8-11
Gao Guoqiang, Luo Guoan, Chen Yuying

Abstract: A microprocessor-based instrument for flow injection analysis is described. Processes such as loading and injection of samples, receiving and processing of signals, printing and displaying of results automatically, are controlled. The instrument was applied in the determination of 100 and 800 ppm of K2Cr2O7, coefficient of variation were 1.42 and 1.09%, respectively.
Spectrophotometry Automation Signal processing Computer