样品厚度对薄膜法X射线荧光光谱测量的影响研究

分别以富集有Cr，Pb和Cd三种元素的尼龙薄膜样品及玻璃纤维滤膜为研究对象，采用滤膜叠加的方式，通过XRF光谱仪测量不同样品厚度下薄膜样品的XRF光谱，根据测得的尼龙薄膜样品中Cr，Pb，Cd元素及玻璃纤维滤膜中Ca，As和Sr元素特征XRF性质的变化，研究样品厚度对薄膜法XRF光谱测量的影响。结果表明：薄膜样品厚度对不同能量区间上元素特征谱线荧光性质的影响并不相同。元素特征谱线能量越大，元素特征X射线荧光穿透滤膜到达探测器的过程中损失越少;但由薄膜样品厚度增加引起的基体效应却越强，相应特征谱线位置处的背景荧光强度就越大，因此样品厚度增加所引起的基体效应对薄膜法XRF光谱测量的灵敏度影响就越大。对于特征谱线能量较低(能量小于7 keV)的元素，以增加薄膜样品厚度的方式来增加待测组分的质量厚度浓度，并不能有效地提高薄膜法XRF光谱测量的灵敏度;对于特征谱线能量较高的元素(能量＞7 keV)，可以通过适当增加样品厚度以增加被测组分的质量厚度浓度的方式来提高XRF光谱测量的灵敏度，薄膜样品厚度在0.96～2.24 mm内，更有利于XRF光谱的测量与分析。该研究为大气及水体重金属薄膜法XRF光谱分析中薄样制备及富集技术提供了重要的理论依据。

Study of the Impact of Sample Thickness on Thin Film Method X-Ray Fluorescence Spectrum Measurement

The mixed samples of nylon film enrichment of Cr,Pb and Cd three elements and glass fiber membrane filter were as the research obj ect.With the method of superposition of membrane filter,the XRF spectra were measured under different thin film samples thicknesses.According the changes of characteristic XRF of Cr,Pb and Cd elements in the mixed sample and Ca, As and Sr elements in glass fiber membranes,the effects of sample thickness on thin film method XRF spectrum measurement were studied.The study results showed that the effects of thin film sample thickness on the fluorescent properties of elements with characteristic spectral lines in different energy ranges were different.The energy of characteristic spectral lines was greater, the loss of element characteristic X-ray fluorescence when it passed through membrane and reached detector was less.But matrix effect caused by thin film sample thickness increase was stronger with the energy of characteristic spectral lines greater.The background fluorescent intensity in corresponding characteristic spectral line location was greater.So the impact of matrix effect caused by sample thickness increase on thin film method XRF spectrum measurement sensitivity was greater.For elements with low energy characteristic spectral lines (energy≤7 keV),the way of increasing thin film sample thickness in order to increase the mass-thickness concentration of component measured,can not effectively improve the sensitivity of thin film method XRF spec-trum measurement.And thin film samples thickness within 0.96 mm is conductive to the measurement and analysis of XRF spec-trum.For element with higher energy characteristic spectra lines(energy>7 keV),the sensitivity of XRF spectrum measure-ment can be appropriately increased by the way of increase thin film sample thickness in order to increase the mass-thickness con-centration of component measured.And thin film samples thickness within 0.96~2.24 mm is more conductive to the measure-ment and analysis of XRF spectrum.The study provides an important theoretical basis for thin sample preparation and enrich-ment technology of thin film method X-ray fluorescence spectrum analysis the atmosphere and water heavy metal.