Chromium can act either as an essential micronutrient or a chemical carcinogen, depending on its
oxidation state. Of the two most stable chromium oxidation states, Cr(VI) is a known carcinogen, while
Cr(III) is an essential element. Determination of total Cr cannot therefore be used to evaluate food
safety of dairy products, as speciation is required for accurate assessment of potential toxicity. In this
study, total Cr was determined by DRC-ICP-MS after mineralisation of freeze-dried milk samples.
Chromabond NH2 ion-exchange columns were used to separate Cr(VI) from Cr(III). During the
separation process, Cr(VI) was selectively adsorbed onto the Chromabond NH2 column. The retained
Cr(VI) was subsequently eluted with two column volumes of 2 M HNO3 and diluted to a final volume
of 10 mL. After separation, the Cr(VI) was quantified by DRC-ICP-MS, using O2 as the reactive gas, to
alleviate polyatomic ion interference. An O2 gas flow rate of 0.85 ml/min and a high-pass rejection
parameter q (Rpq) ¼ 0.5, provided the best compromise signal-to-noise ratio. The method was
validated through determining the recovery in milk samples spiked with Cr(VI). The recoveries were
quantitative and ranged from 96.4 to 99.2%. A whole milk powder reference material (NIST SRM
8435) was used to evaluate the accuracy of the total Cr quantification method. The observed value
showed concordance with the certified value. The limits of detection (LOD) were 0.091 and 0.085 mg/L
for total Cr and Cr(VI), respectively. These findings are important for the determination of maximum
residue levels (MRLs) of Cr(VI) in dairy products.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1001492 |
| Date | 22 January 2009 |
| Creators | Ambushe, AA, McCrindle, RI, McCrindle, CME |
| Publisher | The Royal Society of Chemistry |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | (c) The Royal Society of Chemistry |
| Relation | Journal of Analytical Atomic Spectrometry |
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