| Summary: | 碩士 === 國立中山大學 === 化學系研究所 === 106 === Recently, the detection of harmful substances in foods becomes important because of food safety issues have become more serious. Chromium is an universal metal element. The most toxic Cr species is Cr(VI), a carcinogen, whereas Cr(III) has been considered a micronutrient. Hence, the assessment of chromium species in food is very important. This study will use High-Performance Liquid Chromatograph (HPLC) combine with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to analyze chromium species in foods.
First research, speciation and detection of chromium in wines and beverages was carried out using C18 reversed phase HPLC and ICP-MS in tandem. Isocratic elution using 0.5 mM TBAP, 0.1 mM EDTA and 3% (v/v) methanol at pH 6.9 as mobile phase separated Cr(III) and Cr(VI) in less than 4 min. The determination of chromium by ICP-MS is associated with spectral interferences from 40Ar12C+, 40Ar13C+, etc. Therefore, spectral interferences in ICP-MS at chromium m/z 52 and m/z 53 were reduced using NH3 in Dynamic Reaction Cell system (DRC). The detection limits of Cr(III) and Cr(VI) were 0.06 ng mL-1and 0.07 ng mL-1, respectively. The accuracy of the method has been validated by two river NIST SRMs, NIST SRM 1643c and NIST SRM 1643e. And, the spike recovery was in the range of 99%-101% to demonstrate that the proposed method had good feasibility and accuracy.
Second research, speciation of chromium in rice sample was carried out C8 microbore reversed phase column with membrane desolvation sample introduction system (ARIDUS) coupled with ICP-MS. This study was expected that using ARIDUS to remove the interference of solvents and volatiles to get lower detection limit. Isocratic elution using 0.2 mM TBAP, 0.15 mM EDTA and 10% (v/v) methanol at pH 6.9 as mobile phase separated Cr(III) and Cr(VI) in less than 6 min. Spectral interferences in ICP-MS at chromium m/z 52 and m/z 53 were reduced using NH3 in the DRC. The detection limits of Cr(III) and Cr(VI) were 0.05 ng mL-1and 0.07 ng mL-1, respectively. The established method was applied to determine chromium species present in NIST SRM 1573a Tomato Leaves and rice sample. Chromium species were extracted from all solid sample using microwave heating with 1% (v/v) HF and 1 mM EDTA in mobile phase. HPLC-ARIDUS-DRC-ICP-MS results showed good agreement with total chromium concentrations in extracts obtained by ICP-MS analysis. The spike recovery was in the range of 96%-104% to illustrate that the proposed method had good accuracy and feasibility.
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