Determination of chromium

The chromium in the substance is converted into chromate or dichromate by any of the usual methods. A platinum indicator electrode and a saturated calomel electrode are used. Place a known volume of the dichromate solution in the titration beaker, add 10 mL of 10 per cent sulphuric acid or hydrochloric acid per 100 mL of the final volume of the solution and also 2.5 mL of 10 per cent phosphorus) V) acid. Insert the electrodes, stir, and after adding 1 mL of a standard ammonium iron)II) sulphate solution, the e.m.f. is measured. Continue to add the iron solution, reading the e.m.f. after each addition, then plot the titration curve and determine the end point. 

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DETERMINATION OF CHROMIUM(III) AND IRDN(III) IN A MIXTURE AN EXAMPLE OF KINETIC MASKING 10.66... 

Determination of chromium as lead chromate (precipitation from homogeneous solution) Discussion. Use is made of the homogeneous generation of chromate ion produced by the slow oxidation of chromium(III) by bromate at 90-95 °C in the presence of excess of lead nitrate solution and an acetate buffer. The crystals of lead chromate produced are relatively large and easily filtered the volume of the precipitate is about half that produced by the standard method of precipitation. 

Davidson, I. W. F. and Secrest, W. L. "Determination of Chromium In Biological Materials by Atomic Absorption Spectrometry Using a Graphite Furnace Atomizer". Anal. 

Ross, R. T., Gonzalez, J. G., and Segar, D. A. "The Direct Determination of Chromium In Urine by Selective Volatilization with Atom Reservoir Atomic Absorption". Anal. Chlm. Acta (1973), 63, 205-209. 

Nakayama et al. [38] described a method for the determination of chromium (III), chromium (VI), and organically bound chromium in seawater. They found that seawater in the Sea of Japan contained about 9 x 10 9M dissolved chromium. This was apportioned approximately as 15% inorganic chromium (III), 25% inorganic chromium (VI), and 60% organically bound chromium. 

Reported concentrations of chromium in open ocean waters range from 0.07 to 0.96 xg/l with a preponderance of values near the lower limit. Methods used for the determination of chromium at this concentration have generally used some form of matrix separation and analyte concentration prior to determination [170-173], electroreduction [174,175] and ion exchange techniques [176,177]. 

Determination of chromium by many of the methods cited above is problematic. Variable and nonquantitative recovery with chelation-solvent extraction... 

The chemiluminescence technique has been used to determine trivalent chromium in seawater. Chang et al. [187] showed Luminol techniques for determination of chromium (III) were hampered by a salt interference, mainly due to magnesium ions. Elimination of this interference is achieved by seawater dilution and utilising bromide ion chemiluminescence signal enhancement (Fig. 5.7). The chemiluminescence results were comparable with those obtained by a graphite furnace flameless atomic absorption analysis for the total chromium present in samples. The detection limit is 3.3 x 10 9 mol/1 (0.2 ppb) for seawater with a salinity of 35%, with 0.5 M bromide enhancement. 

Diphenylcarbazone and diphenylcarbazide have been widely used for the spectrophotometric determination of chromium [ 190]. Crm reacts with diphenylcarbazone whereas CrVI reacts (probably via a redox reaction combined with complexation) with diphenylcarbazide [ 191 ]. Although speciation would seem a likely prospect with such reactions, commercial diphenylcarbazone is a complex mixture of several components, including diphenylcarbazide, diphenylcarbazone, phenylsemicarbazide, and diphenylcarbadiazone, with no stoichiometric relationship between the diphenylcarbazone and diphenylcarbazide [192]. As a consequence, use of diphenylcarbazone to chelate Crm selectively also results in the sequestration of some CrVI. Total chromium can be determined with diphenylcarbazone following reduction of all chromium to Crm. 

A standard contact time of 4 h was found to be necessary for the quantitative coprecipitation of chromium on ferric oxide. The results of triplicate determinations of samples taken from six locations in the Sydney area are listed in Table 5.3. The rsd values for the determinations of chromium (III), chromium (VI), and total dissolved chromium were generally 10.0%, 5.0%, and 5.0% respectively. 

Mugo and Orlans [197] have discussed shipboard methods for the determination of chromium (III) and total chromium in seawater by derivatisation with trifluoroacetylacetone followed by gas chromatography using an electron capture detector. 

Nakayama et al. [201] have described a method for the determination of chromium (III), chromium (VI), and organically bound chromium in seawater. 

Cabon and Le Bihan [711] studied the effects of transverse heated AAS and longitudinal Zeeman effect background correction in sub xg/l determination of chromium, copper, and manganese in seawater samples. 

The application of the Chelex 100 resin separation and preconcentration, with the direct use of the resin itself as the final sample for analysis, is an extremely useful technique. The elements demonstrated to be analytically determinable from high salinity waters are cobalt, chromium, copper, iron, manganese, molybdenum, nickel, scandium, thorium, uranium, vanadium, and zinc. The determination of chromium and vanadium by this technique offers significant advantages over methods requiring aqueous final forms, in view of their poor elution reproducibility. The removal of sodium, chloride, and bromide allows the determination of elements with short and intermediate half-lives without radiochemistry, and greatly reduces the radiation dose received by personnel. This procedure was successfully applied in a study of... 

Mattioli G. S. and Bishop F. (1984). Experimental determination of chromium-aluminum mixing parameter in garnet. Geochim. Cosmochim. Acta, 48 1367-1371. 

Peterson, M.L. Brown Jr., G.E. Parks, G.A. (1997) Quantitative determination of chromium valence in environmental samples using XAFS spectroscopy. In Voigt, J.A. Bunker, B.C. Casey,W.H. Wood,T.E. Crossey, L.J. (eds.) Aqueous chemistry and geochemistry of oxides, oxyhydroxides, and related materials. Materials Research Society, Pittsburgh... 

Figure 9.31 (a) Determination of chromium in DNA using flow injection ICP-SFMS (sample loop ... 

J. C. Rodriguez-Garcia, J. Barciela-Garcia, C. Herrero-Latorre, S. Garcia-Martin and R. M. Pena-Crecente, Direct and combined methods for the determination of chromium, copper and nickel in honey by electrothermal atomic absorption spectroscopy, J. Agric. Food Chem., 53(17), 2005, 6616-6623. 

The effects of soil sample preparation procedures for the determination of chromium in soils have been reported [38]. The optimum conditions included the use of an homogeneous sample with a mass of less than 4 kg, a grain diameter of less than 0.25 mm, digestion with a solution of nitric acid plus perchloric acid (3 2) and hydrochloric acid after dry ashing, with the addition of 1% lanthanum or 1% ammonium chloride to eliminate interferences. 

The determination of chromium is also discussed under Multi-Metal Analysis of Soils in Sect. 2.55 (atomic absorption spectrometry), Sect. 2.55 (inductively coupled plasma atomic emission spectrometry), Sect. 2.55 (emission spectrometry), Sect. 2.55 (photon activation analysis), Sect. 2.55 (neutron activation analysis), and Sect. 2.55 (differential pulse anodic stripping voltammetry). 

Prokisch et al. [85] described a simple method for determining chromium speciation in soils. Separation of different chromium species was accomplished by the use of acidic activated aluminium oxide. Polarographic methods have been applied in speciation studies on chromium(VI) in soil extracts [86]. Mi-lacic et al. [88] have reviewed methods for the determination of chromium(VI) in soils. 

Kalembkiewicz and Filar [93] have reported on the effect of the soil sample preparation procedure on the determination of chromium in soils. 

Marques [94] has reviewed literature on chromium speciation in soils. The determination of chromium is also discussed under Multi-Metal Analysis of Soils in Sect. 2.55. 

The error of the AAS determination of chromium in river water with a determined mean concentration of 4.8 (ig L 1 is acceptable for this particular environmental purpose. The highest variance percentage arises as a result of centrifugation. The sampling error arising from river inhomogeneity is relatively small in this particular environmental situation. 

Cox, A., Cook, I.G. and McLeod, C.W. (1985) Rapid sequential determination of chromium (III)-chromium (VI) by flow injection analysis-inductively coupled plasma atomic-emission spectrometry. Analyst, 110, 331-333. 

Nakata, F., Hara, S., Matsuo, H., Kumamaru, T. and Matsushita, S. (1985) Fractional determination of chromium (III) and chromium (VI) via ion chromatography with inductively coupled plasma atomic-emission spectrometric detection. Anal. Sci., 1, 157-160. 

Sperling, M., Xu, S. and Welz, B. (1992) Determination of chromium (III) and chromium (VI) in water using flow injection on-line preconcentration with selective adsorption on activated alumina and flame atomic absorption spectrometric detection. Anal. Chem., 64, 3101-3108. 

Emstberger, H., H. Zhang, and W. Davison. 2002. Determination of chromium speciation in natural systems using DGT. Anal. Bioanal. Chem. 373 873-879. 

Batley, G.E. and J.P Matousek. 1980. Determination of chromium speciation in natural waters by electrodeposition on graphite tubes for electrothermal atomization. Anal. Chem. 52 1570-1574. 

International Standard Organization. 1994. Water quality. Determination of chromium(VI). Spectrometric method using 1,5-diphenylcarbazide. ISO 11083. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

European Standard. 1996. Water quality. Determination of chromium. Atomic absorption spectrometric methods. EN 1233. European Committee for Standardization, Brussels, Belgium. 

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