Determination of Chromium (Ⅲ) and Chromium (Ⅵ) in Dairy Products by HPLC-ICP-MS
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Abstract:
A method was developed for the simultaneous determination of chromium(Ⅲ) and chromium(Ⅵ) in dairy products by high performance liquid chromatography(HPLC) coupled with inductively coupled plasma-mass spectrometry(ICP-MS). The sample was boiled in EDTA buffer solution, cooled down and centrifuged at 8000 r/min for 10 min to separate the protein. Then the supernatant was filtrated through 0.45 μm filter membrane, and chromium(Ⅲ) and chromium(Ⅵ) were simultaneously extracted. Using NH4NO3 as mobile phase (pH=7.0~7.2), Chromium(Ⅲ) and chromium(Ⅵ) were separated and detected in 4 min by HPLC-ICP-MS at a flow rate of 0.6 mL/min. The effects of various pretreatment conditions on test results were researched. The amount of EDTA should be excessive to eliminate the influence of calcium, magnesium and other elements. The complexation rate of EDTA with Chromium(Ⅲ) was significantly increased by boiling, but the time should not be too long, and 2~3 min was appropriate. The two chromium species had good recoveries and separation effect under pH 7.0~7.2. The results showed that the linear ranges for Chromium(Ⅲ) and chromium(Ⅵ) were between 0.2 and 20 μg/L with linear coefficients more than 0.9995, and the detection limits were 0.034 and 0.066 μg/L. The method had a simple pretreatment procedure, high sensitivity and good accuracy and precision.
