Kaolins, clays, sepiolites, nitrates, carbonates, and so forth are commonly used in the food industry, either as additives or technological contributories in fining and bleaching processes. These materials must be thoroughly controlled as they can contain some heavy metals that must be in very low concentration as they are toxic to humans. Methods using ICP‐OES, AAS, and ICP‐MS for the determination of trace elements are quite tedious and time‐consuming, due to the necessity of a previous sample treatment to extract the analyte in an aqueous matrix, and non‐ecological as this sample treatment implies the use of acids and thermal processes. A robust WD‐XRF method for accurate quantitative determination of Pb, Cd, Ni, Cr, Hg, and As was developed, reaching the following detection limits: 1 mg·kg⁻¹ for Pb and Cd, 2 mg·kg⁻¹ for Cr and As, and 3 mg·kg⁻¹ for Ni and Hg. For that, a thorough study for the optimisation of the sample preparation was undertaken, studying different kind of binders for pellet preparation, as well as the optimisation of the measurement conditions to be able to reach the requirements stated in food regulation. Besides, an exhaustive search of reference materials was also conducted in order to be able to construct appropriate calibration curves. The methodology was validated both by analysing certified reference materials different from the ones used for calibration and by the use of different analytical techniques to get independent results.

中文翻译：

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用于定量痕量分析的WD‐XRF方法的开发和验证：在食品工业中的应用

高岭土，粘土，海泡石，硝酸盐，碳酸盐等在食品工业中通常用作添加剂或在精制和漂白过程中的技术贡献。这些材料必须被彻底控制，因为它们可能包含一些重金属，这些重金属必须以非常低的浓度存在，因为它们对人体有毒。使用ICP-OES，AAS和ICP-MS进行痕量元素测定的方法非常繁琐且耗时，这是因为必须事先进行样品处理才能将分析物从水性基质中提取出来，而且这种方法具有非生态性。样品处理意味着使用酸和热过程。开发了一种可靠的WD‐XRF方法，用于准确定量测定Pb，Cd，Ni，Cr，Hg和As，达到以下检测极限：1 mg·kg ^-1对于Pb和Cd，Cr和As为2 mg·kg ^-1，对于Ni和Hg为3 mg·kg ^-1。为此，对样品制备的最优化进行了彻底的研究，研究了用于颗粒制备的不同种类的粘合剂，以及对测量条件的最优化以能够达到食品法规中规定的要求。此外，还对参考材料进行了详尽的搜索，以便能够构建适当的校准曲线。通过分析与校准所用的认证参考物质不同的认证参考物质，以及通过使用不同的分析技术来获得独立的结果，从而验证了该方法的有效性。