Title: Chromium Analysis

Key words: sodium heparin, spectrophotometer, matrix modification, contamination, chromium status, chromium body pool

Date: July 2000

Category: 14. Measurement

Type: Article

Author: Dr van Rhijn

 

Chromium Analysis

Fasted samples (10–12 hours) of urine (second morning sample) and blood (in sodium heparin), with the latter centrifuged & aliquoted, should be stored (lyophilised) at –20oC in sealed plastic bags containing ice to maintain humidity, if analysis is delayed.

Reputable laboratories1 ensure stringent sample preparation (non-powdered gloves), using Cr free containers (plastic cannula or siliconised needles) to prevent contamination2, ultra-pure reagents, acid-washed pipettes and sample cups, in a class-100 laminar flow hood high humidity atmosphere to reduce the build-up of static.

Cr analysis is best performed using a sensitive and specific Zeeman graphite furnace electrothermal atomic absorption spectrophotometer (GFAAS)3, measuring one item at a time by sample heating and vaporising. The results can then be compared with an external quality control reference standard4. Initial GFAAS5 systems, which measured background absorption from the sample matrix proved inaccurate. The improved analysis with Tungsten-halogen correctors has also now been superceded by Zeeman-effect background correction. Matrix modification, using Mg(NO3)2 & Pd(NO3)2 solutions, for the analysis of the microwave-assisted wet acid digested procedure improved measurement accuracy6.

Neutron activation analysis (enrichment by co-precipitation with metal carriers after irradiation) is also used7. Interpretation remains difficult due to low Cr levels in biological tissues8 which do not reflect chromium status or metabolically active chromium body pools9.

References

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2. Veillon, C.. Analytical chemistry of chromium. Sci. Total Environ. 1989; 86: 65 – 68.

3. Pineau, A. et al.. Total chromium in the human lens. Determination with Zeeman electrothermal atomic absorption spectrometry following mineralization in a mini-autoclave. Biol. Trace. Elem. Res. 1992; 32: 139 - 143.

4. Morris, B.W. et al.. Chromium Homeostasis in Patients with Type I (NIDDM) Diabetes. J. Trace Elements. Med. Biol. 1999; Vol. 13, pp. 57 – 61.

5. Horng, C.J. & Lin, S.R.. Determination of urinary zinc, chromium, and copper in steel production workers. Biol. Trace Elem. Res. 1996; 55:3, 307 - 314.

6. Alvarado, J. et al.. Determination of Cd, Cr, Cu, Pb and Zn in human semen by graphite furnace atomic absorption spectrometry after microwave sample dissolution. J. Trace Elem. Electrolytes Health Dis. 1991; 5:3, 173 - 180.

7. Lavi, N. & Alfassi, Z.B.. Determination of trace amounts of cadmium, cobalt, chromium, iron, molybdenum, nickel, selenium, titanium, vanadium and zinc in blood and milk by neutron activation analysis. Analyst. 1990; 115:6, 817 - 822.

8. Stoecker, B.J.. Chromium. In: Ziegler E. & Filer L. Present knowledge in Nutrition. Seventh Edition. ILSI Press. Washington. 1996; Chapter 34 pp 344 – 352.

9. Iyengar, G.V.. Nutritional chemistry of chromium. Sci. Total Environ. 1989; 86: 69 – 74.