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trifluoroacetylacetone. Chromium is an essential element in human diet and appears to be associated
with glucose metabolism and/or insulin response. The concentrations of interest are well below 1 ng/g
and consequently there are a limited number of analytical techniques available for such assays. About 3
g of urine was spiked with an appropriate amount of a Cr-enriched standard and 50 µl of magnesium
50
nitrate. The mixture was evaporated to dryness at 90°C, 100 µl concentrated nitric acid was then added,
and heating continued. When nearly dry, the residue was treated with 50 µl aliquots of hydrogen
peroxide, and again heated until the dry residue was white. The residue was then dissolved in 50 µl of 6
M hydrochloric acid, and again evaporated to dryness. The residue was redissolved in 50 µl of 1 M
hydrochloric acid and 1 ml of 1 M ammonium acetate buffer, and 100 µl of trifluoroacetylacetone
added. The mixture was then heated in capped tubes at 70°C for 1.5 hours and the chelate then extracted
with n-hexane. The excess reagent was removed by washing with 0.1 M NaOH, and the hexane layer
washed with water. After evaporating to dryness, the residue was taken up in 25 µl of hexane and an
appropriate aliquot of the resulting solution injected onto the column. The GC employed was the
Finnigan Model 9610 and the mass spectrometer the Finnigan MAT Model 4000. The detection limit of
the method was found to be 0.03 ng/g. By the nature of the analysis, the method is highly specific i.e.
due to the combination of the chelating, gas chromatographic and mass spectrometric selectivity). The
technique can also be used in tracer procedures that are employed to follow metabolic pathways in
nutrition studies.

GC/MS Tandem Systems in Environmental Analysis

As many environmental contaminants have relatively low molecular weights and often involve organic
chlorine or phosphorus compounds, they are often relatively volatile, and so they lend themselves to
measurement by GC/MS tandem systems. The most important and frequently monitored environmental
samples are those taken from the many and various sources of water. Water is not only an essential
domestic requirement but is also the main means by which polluting materials are removed from the
land. It follows, that a water analysis can