Division of Science and Engineering for Materials, Department of Chemistry and Bioengineering, Osaka Metropolitan University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan.
Analyst. 2022 Nov 7;147(22):5130-5137. doi: 10.1039/d2an01290a.
Total reflection X-ray fluorescence (TXRF) analysis is conducted to determine trace elements in a sample solution, which is dropped onto a substrate and dried. Therefore, the form of the residue affects the quantitative results. The absorption of X-ray fluorescence (XRF) follows the Lambert-Beer law; the absorption effect of XRF in a thick residue (dotted-type residue) is stronger than that in a thin residue (film-type residue). The absorption effect is particularly remarkable during the determination of low- elements in a high-elemental concentration solution. In this study, we propose a new film-like-residue preparation process based on the freeze-drying method to obtain accurate TXRF results. The sample solution is dropped onto the substrate and inserted into a chamber. The chamber is cooled using liquid nitrogen; resultantly, an aliquot of the sample is frozen. The chamber is depressurized using a vacuum pump, and the freeze-dried residue is prepared by maintaining the chamber at room temperature. To evaluate the efficiency of the freeze-drying-based method for sample preparation for TXRF analysis, we prepare a multi-element solution containing high-elemental concentration components. For the residue prepared using the freeze-drying method, the relative standard deviations of the quantitative values and the minimum detection limits are improved because the absorption effect is weakened. The sample preparation process based on the freeze-drying method facilitates accurate TXRF analysis of high-elemental concentration solutions and can be applied for the analysis of trace elements in different types of solutions such as environmental water and wastewater.
全反射 X 射线荧光（TXRF）分析用于测定滴落在基底上并干燥后的样品溶液中的微量元素。因此，残留物的形态会影响定量结果。X 射线荧光（XRF）的吸收遵循朗伯-比尔定律；在厚残留物（点型残留物）中，XRF 的吸收效果强于在薄残留物（膜型残留物）中。在高浓度元素溶液中测定低元素时，吸收效果尤为显著。在本研究中，我们提出了一种基于冷冻干燥法的新型膜状残留物制备工艺，以获得准确的 TXRF 结果。将样品溶液滴落在基底上并插入腔室中。使用液氮冷却腔室；结果，样品的一部分被冷冻。使用真空泵对腔室进行减压，并通过将腔室保持在室温来制备冻干残留物。为了评估基于冷冻干燥法的 TXRF 分析样品制备方法的效率，我们制备了一种含有高浓度元素成分的多元素溶液。对于使用冷冻干燥法制备的残留物，由于吸收效果减弱，定量值的相对标准偏差和最小检测限得到改善。基于冷冻干燥法的样品制备工艺有利于对高浓度元素溶液进行准确的 TXRF 分析，并且可应用于不同类型溶液（如环境水和废水）中微量元素的分析。
