Speciation of chromium

This subject is reviewed more in detail in the chapter on speciation by P.E. Gardiner and H.T. Delves. 

Speciation of Cr in biomaterials means differentiation between the various species of the element. In fact this can be understood in two ways. Firstly speciation can be studied by separating the proteins and analyzing the amount of Cr in them. Secondly it can consist of a search for the oxidation state in which Cr is transformed or bound to macromolecular compounds. These studies are difficult because of the variety of chemical compounds in biological materials which interact with Cr. 

Several speciation procedures for Cr(lll) and Cr(VI) can be found in the literature. They are based on the distinction between cationic Cr(lll) and anionic Cr(VI) forms. 

Mianzhi and Barnes (1983) describe a method that starts with two distinct samples of the biological fluid. One is treated with polydithiocarbamate (PDTC) resin at pH 5, which binds the Cr(VI), the second is treated with polyacrylamidoxime (PAAO) resin, also at pH 5, to bind the Cr(lll). The resins are subsequently digested in HNO3 and the Cr content is measured by ICP-OES. 

Minoia et al. (1983) used a liquid anion exchanger Amberlite LA 1 or LA 2 in isobutyl methyl ketone and 6 mol/L HCI mixture, which was added to the aqueous biological specimen (in casu urine). After extraction of the anions, centrifugation and separation of both phases, all Cr(VI) was bound to the organic phase, whereas Cr(lll) was present in the aqueous phase. 

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Ahern et al. [ 195] have discussed the speciation of chromium in seawater. The method used coprecipitation of trivalent and hexavalent chromium, separately, from samples of surface seawater, and determination of the chromium in the... 

Howe JA, Loeppert RH, DeRose VJ, Hunter DB, Bertsch PM. Localization and speciation of chromium in subterranean clover using XRF, XANES, and EPR spectroscopy. Environ. Sci. Technol. 2003 37 4091 1097. 

Nico. R S. Werner, M. Anastasio, C. Marcus, M. A. Chemical Speciation of Chromium in Ambient Aerosol Particles. Proceedings of the 233rd American Chemical Society National Meeting, Chicago, IE, March 25-29, 2007. 

Nakayama, E., Kuwamoto, T., Surubo, S.T. and Fujinaga, T., 1981. Chemical speciation of chromium in seawater. Anal. Chim. Acta, 30 401-404. 

Chromium (Cr+6) TT luminescent bacteria are exposed to assess the influence of pH speciation of chromium on toxicity response. B (Villaescusa et ah, 1997)... 

Barnowski, C., Jakubowski, N., Stuewer, D. and Broekaert, J.A.C. (1997) Speciation of chromium by direct coupling of ion exchange chromatography with inductively coupled plasma mass spectrometry. J. Anal. At. Spectrom., 12, 1155-1161. 

Sophisticated analytical procedures for the speciation of chromium (Prokisch et al., 1995) and platinum (Michalke et al., 1997) in the soil solution or soil extracts have also been described. 

Difficulties have been observed in the preservation of samples for speciation of chromium. Chromium speciation in seawater was determined on board ship shortly after samples had been collected (Abollino et at., 1991). Some samples were frozen, and analysed later in a laboratory. However, significantly lower concentrations of Crvl were observed in these latter samples. Thus, sea-going analytical methods for the determination of Crm and total chromium are of particular importance (Mugo and Orians, 1993). The volatile trifluoroacetyl-acetone derivative of Crm was formed and then concentrated by extraction into toluene. Chromium was determined by means of a gas chromatograph equipped with an electron capture detector. Total chromium was determined as Cr111 after reduction. The detection limits were 0.062 and 0.255 nmol dm 3 total chromium. A useful method was described for sampling natural water in the field, and for the preservation of Crm and Crvl species for subsequent analyses in a laboratory (Cox and McLeod, 1992). Water samples were drawn through small columns packed with activated alumina, which had been prepared previously. Chromium species were retained on the columns. 

Girard, L. and Hubert, J. (1996) Speciation of chromium (VI) and total chromium determination in welding dust samples by flow injection analysis coupled to atomic absorption spectrometry. Talanta, 43,1965-1974. 

Pantsar-Kallio, M. and P.K.G. Manninen. 1996. Speciation of chromium in waste waters by coupled column ion chromatography-inductively coupled plasma mass spectrometry. J. Chromatogr. A 750 ... 

Yang, W.P., ZJ. Zhang, and W. Deng. 2003. Speciation of chromium by in-capillary reaction and capillary electrophoresis with chemiluminescence detection. J. Chromatogr. A 1014 203-214. 

Dogutan, M., H. Filik, and I. Tor. 2003. Preconcentration and speciation of chromium using a melamine based polymeric sequestering succinic acid resin Its application for Cr(VI) and Cr(IH) determination in... 

Chromium is used in a number of industrial processes and, as noted, has toxicity that is highly dependent on its speciation. The combination of ion chromatography and ICP-MS detection has been used to measure Cr(III) and Cr(VI) in waste water [412]. Ion-pairing HPLC-ICP-MS was used to measure chromium species in seawater [413], Speciation of chromium dyes was also reported by HPLC-ICP-MS [414]. 

R. M. Cespon Romero, M. C. Yebra-Biurrun, M. P. Bermejo-Barrera, Preconcentration and speciation of chromium by the determination of total chromium(III) in natural waters by flame atomic absorption spectrometry with a chelating ion-exchange flow injection system, Anal. Chim. Acta, 327 (1996), 37-45. 

IPC separation of monomethyl and mercuric Hg in biotic samples by formation of their thiourea complexes, coupled to cold vapor generation and atomic fluorescence detection, was successfully validated [18]. The coupling of IPC with atomic absorption spectrometry was also used for online speciation of arsenic compounds employing hydride generation [17]. In the analytical speciation of chromium using in... 

Aguilar, RJ.A. et al. Analytical speciation of chromium in in-vitro cultures of chromate-resistant filamentous fungi. Anal. Bioanal Chem. 2008, 390, 1-8. 

Ambushe, A.A., McCrindle, R.I., McCrindle, C.M.E. Speciation of chromium in cow s milk by solid-phase extraction/dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS). JAAS 24, 502-507 (2009)... 

Work on the speciation of iron and zinc in vegetable products is just beginning (23), and some progress is being made on the speciation of chromium (24) but not enough data have been accumulated to be of interest to the nutritionist. Speciation analysis has produced impressive advances in the toxicology of heavy metals. Similar advances can be expected in trace element nutrition if the diflBculties of methodology can be overcome. 

Other methods of speciation of chromium in water samples lie in the use of anion exchange resins, which were shown by Barnowski et al. [568] to retain both the Cr111 and the CrVI species. This approach has the advantage that chloride ions which could possibly be present are retained and accordingly do not cause spectral interferences, e.g. when determining preconcentrated iron species. 

Pappert E., Flock J. and Broekaert J. A. C. (1999) Speciation of chromium in solid materials with the aid of soft-x-ray spectrometry,... 

There have been several reports [6-10] that describe the speciation of chromium. Many of these reports described the use of DC plasma atomic emission (DCPAE), ICP-AE, and atomic absorption (AA) selective-type detection. UV/VIS detection has also been extensively used. Atomic emission detection has been found to be very promising due to its selectivity and low detection limits. 

Exactly what is the analytical problem and what is the minimum analytical information needed to provide a reasonable answer In this connection it is well to categorize the type of analysis desired oxyhalides in drinking water, arsenic speciation in drinking water, speciation of chromium in plating baths, etc. 

Fig. 2.9 Speciation of chromium in water, (a) Scheme of the configuration (b) flow diagram of the program. 

In its reversed mode, FIA is fully adaptable to Industrial process control [49-51], and to studies of the speciation of various elements In waters [102]. One of the most promising developments in the latter area is the speciation of chromium by means of the configuration depicted in Fig. 6.20. This uses a combined giass-calomel microelectrode incorprorated in the sample stream prior to the simultaneous injection of the reagents (Ce and 1,5-diphenylcarbazide for Cr3+ and Cr(VI). The data obtained for the concentration of these two species, together with the sample pH and the constants corresponding to the equilibria in which both oxidation states are involved, allow the calculation of the concentration of up to nine different chromium species aquo complexes and hydroxylated forms of Cr(III) and ionic, molecular and dimeric forms of Cr(VI) [103]. 

Fig. 15.8 FIA configurations for the off-line speciation of chromium, (a) With a splitting point (A) and a dual-beam detector (a.1) with two cells aligned with the light path (a.2) with a merging point prior to a single flow-cell (a.3). (b) Sequential determination with the aid of a selecting valve. DPC diphenylcarbazide Ox oxidant [Ce(IV)] q flow-rate Vi injection valve L and 0 reactor length and inner diameter V2 selecting valve W waste. (Reproduced from [37] with permission of Elsevier).

A number of analytical methods have been developed to identify and quantitate chromium in environmental media in response to various state, federal and international mandates. Speciation of chromium is important because of marked differences in both toxicity and environmental behavior. Current methodologies have been reviewed (Cornelis 1996 Vitale et al. 1997). 

Baiasoiu CF, Zagury GJ and Deschenes L (2001) Partitioning and speciation of chromium, copper, and arsenic in CCA-contaminated soils influence of soil composition. Sci Total Environ 280 239-255. 

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