The Analytical Biochemistry of Chromium
Sidney A. Katz
1991
Environmental Health Perspectives
The essentiality and carcinogenicity of chromium depend on its chemical form. Oxidation state and solubility are particularly important in determining the biological effects of chromium compounds. For this reason, total chromium measurements are of little value in assessing its nutritional benefits or its toxicological hazards. Aqueous sodium carbonate-sodium hydroxide solutions have been successfully used for extracting hexavalent chromium from a variety of environmental and biological
more »
... while preserving its oxidation state. Typical recoveries are 90 to 105% in samples spiked with both trivalent and hexavalent chromium. Determination of hexavalent chromium after extraction with sodium carbonate-sodium hydroxide solution, coupled with the determination of total chromium after nitric acid-hydrogen peroxide digestion, has been applied to the evaluation of chromium speciation in airborne particulates, sludges, and biological tissues. In general, the bioavailability of an element is determined by its chemical form. Oxidation state and solubility are particularly important factors for bioavailability. For this reason, it is frequently necessary to establish the trace element composition of agricultural, biological, clinical, and environmental materials in both qualitative and quantitative terms. In this reference frame, chromium is of special interest because it is both an essential nutrient and a carcinogen. Dietary deficiency of trivalent chromium has been associated with faulty sugar metabolism in the human, and the inhalation of some moderately insoluble hexavalent chromium compounds has been correlated with increased incidences of lung cancer. Chromium is an essential trace element in the human diet. It is poorly absorbed, and the concentrations of chromium in various tissues and fluids are normally quite low. A quarter of a century ago, Mertz (1) proposed a biochemical role for trivalent chromium (Cr"I') in the metabolism of glucose. Subsequently, a glucose tolerance factor was identified as a complex of trivalent chromium with niacin and three amino acids (2). The available data show trivalent chromium compounds to be less toxic than those of hexavalent chromium (3-5). The carcinogenicity of various hexavalent chromium (CrvI) compounds in human and animal models is well documented. Acute and chronic toxicity problems associated with exposure to hexavalent chromium compounds include ulceration of the skin, perfo-
doi:10.2307/3431132
fatcat:3asejla5fjebpmgjrxj7kwqz5y