食鹽廣泛用於食品工業及日常烹調，會因環境污染而殘留重金屬進而造成健康危害。衛生福利部於「食品中污染物質及毒素衛生標準」訂有食鹽中重金屬限量。早期檢驗方法受限於當時檢測技術，檢驗方法須因應元素特性，以不同前處理搭配對應之儀器進行分析，故分散為汞之檢驗、砷之檢驗及銅、鉛及鎘之檢驗等3篇檢驗方法。為增加檢驗效益，本研究優化及整併上述方法，建立以感應耦合電漿質譜儀（ICP-MS）同步分析食鹽中銅、砷、鎘、汞及鉛等5種元素之檢驗方法。將食鹽檢體經微波酸輔助消化，利用現行ICP-MS可耐受少量鹽類特性，省略離子交換樹脂繁瑣耗時之除鈉步驟，另以含鹽硝酸溶液配製檢量線，使能與檢液匹配並搭配多重內標校正，增加結果準確性。檢量線之線性範圍為0～25 ng/mL，其判定係數皆大於0.9996。定量極限部分，銅及砷均為0.05 mg/kg，鎘、汞及鉛則均為0.02 mg/kg；選擇空白食鹽檢體執行添加回收試驗，結果顯示，銅、砷、鎘、汞及鉛之平均回收率介於97.7～115.2%之間，變異係數皆小於10%，均符合本署「食品化學檢驗方法之確效規範」。另檢驗6件市售食鹽檢體，結果均未超過法規限值。本研究所建立之檢驗方法簡單、快速，符合現今檢驗趨勢，可應用於食鹽中重金屬含量之檢驗。

Edible salt is widely used in the food industry and daily cooking. Because residues of heavy metals in salt from pollutant accumulation may cause health hazards for human beings, the Ministry of Health and Welfare (Taiwan) regulates the maximum levels of metals in salt based on “Sanitation Standard for Contaminants and Toxins in Food”. Due to immature technology development, three standard methods are announced for the determination of diverse elements such as mercury (Hg), arsenic (As), copper (Cu), lead (Pb), and cadmium (Cd) in edible salt. In other words, different processing methods and instruments are employed in the analysis of metals in edible salt according to their characteristics. To enhance the analytical throughput, this study proposed a method combining inductively coupled plasma-mass spectrometry (ICP-MS) with microwave digestion for simultaneous determination of five heavy metals, i.e., Hg, As, Cu, Pb, and Cd, in edible salt. In view of high tolerance to saline matrix in current ICP-MS instrumentation, the sample processing involving removal of sodium-rich matrix can be eliminated. The accuracy of the analytical results was further improved by multi internal standard addition and matrix matching. The linear range of the calibration curve was from 0 to 25 ng/mL and every coefficient of determination was greater than 0.9996. The limits of quantification for Cu and As were 0.05 mg/kg, and those for Cd, Hg, and Pb were 0.02 mg/kg. The spike recoveries for Cu, As, Cd, Hg, and Pb were ranged from 97.7 to 115.2%, and every coefficient of variation was less than 10%. All obtained results were satisfied with the “Guidelines for the Validation of Food Chemical Analysis Methods” launched by the Food and Drug Administration (Taiwan). The analytical results of six commercial edible salt were also in compliance with regulations. Obviously, the method developed in this study was prevailing, simple, fast, and capable of accurate determination of heavy metals in in edible salt.