XRF能量色散X射线荧光光谱仪的基质基体干涉效应分析

XRF能量色散X射线荧光光谱仪的基质基体干涉效应分析

a) 激发辐射的散射过程会影响样品中元素的特征辐射强度。这是因为散射过程会影响光谱的背面。

看法。此外，还有两个主要影响：

b) 样品中的激发辐射被吸收，其他元素（基质）发出由此产生的或荧光辐射。

c) 样品中其他元素的二次激发（增强）。

— 塑料材料：塑料样品中的基质会影响分析物的特征 X 射线强度，主要来自：

— 一次辐射的散射（主要是不连续的），这对背景光谱有很大的贡献

— 在荧光辐射中的吸收，主要是由 PVC 中的 Cl、Ca、Ti、Zn、Sn 等添加元素引起的，来源于

阻燃剂中的溴和锑

— 由 Sb、Sn 和 Br 等元素引起的二次激发

— 金属：金属样品中由初级激发引起的散射不起重要作用。基质效应主要是由吸收和次要引起的

对于不同的金属基材，这些效果是不一样的。下面列出了一些不同的基材。

典型元素：

— 铁合金：Fe, Cr, Ni, Nb, Mo, W,...

— 铝合金：Al、Mg、Si、Cu、Zn、...

— 铜合金：Cu、Zn、Sn、Pb、Mn、Ni、Co、...

— 焊料合金：Pb、Cu、Zn、Sn、Sb、Bi、Ag、...

— 锌合金：锌、铝、…

— 贵金属合金：Rh、Pd、Ag、Ir、Pt、Au、Cu、Zn……

— 电子元件和印刷电路板：原则上，包括在聚合物和金属中发生的所有影响。

d) 此外，样品中测试元素的特征光谱强度会受到其他元素的干扰。典型的干扰如下：

— 镉：可能的干扰来自溴、铅、锡、锑

— 铅：可能的干扰来自溴

— 汞：可能的干扰来自样品中的溴、铅以及高浓度的钙和铁

— 铬：可能的干扰来自氯

— 溴：可能的干扰来自铁和铅

e) 基质效应对检测限（LOD）的影响

样品均匀度

XRF 分析点的均匀性取决于样品在仪器激发的体积内的物理均匀性。测试样品时

可以应用以下三项来实现均匀性。

a) 大表面样品（适用于所有样品）： — 评估用于 XRF 分析的测试样品的均匀性是显而易见的、必要的和有用的。例如，任何颜色。

形状和外观相对统一的物体在测试前不需要进行机械采样。典型的测试可能很大而且

长塑料物体，如 CRT 监测盒、塑料外壳、厚带、金属合金等。关于测试物体的任何附加信息都可以

例如，为了建立其均匀性，许多塑料和金属表面都有涂层。一些塑料表面被金属化，测试

样品被包裹在里面。在这种情况下，样品需要进行一定程度的拆卸，使用未涂层或未金属化的塑料

去测试。金属表面可以镀其他金属，如镀锌钢、镀镉钢、镀铬钢和镀铬铝。这些镀在

铬的金属会有比较高的读数，铬的可能低一点，因为铬层通常很薄。如果要分析基数

材料，则应去除所有涂层。

b) 小表面样品：

— 小的电子元件也可以被认为是统一的，只要分析物可以被仪器激发并且只分析选定的那些

位置、样品也将显示均匀性，例如塑料封装、单独的焊料或聚合物/环氧树脂的单独区域。

在分析基材时，要特别注意避免金属镀层、聚合物涂层或油漆的干扰。如果有涂层，则应涂漆

该层被物理移除。

c) 涂层和薄样品：

— 样品太小或太薄都可能导致质量或厚度下降，导致结果无法使用。测试这么小的质量样本

（如小螺丝），将样品放入样品杯中。同样，在测试薄样品时，将样品堆叠至厚。

达到测试所需的最小厚度，然后进行常规测试。一般规则是所有样品都应*覆盖测试的光谱

对于窗户，聚合物和轻金属（例如铝、镁或钛）的最小厚度为 5mm，液体的最小厚度为 15mm，其他合金的最小厚度为 1mm。细线和带状电缆的绝缘不能算是均匀的，金属导体必须是

测量前完成。另一方面，任何铜芯直径大于5mm的电源线都可以认为是统一的。金属可以在分离后进行测量。

工作人员知道，可以通过校准材料和光度计的结构来分析如此复杂的表面结构，因此也可以使用一些金属涂层。

待分析。例如，已知涂层是 SnAgCu（全镀金）铜（全镀金）。锡合金可用于分析，

只要仪器可以校准这种类型的样品。人们普遍认为，大多数 XRF 敏感设备无法检测到 Cr 转化涂层，除非该涂层的厚度至少为几百纳米。由于不同的仪器需要不同尺寸的样品变化，建议光度计的操作人员查阅仪器手册或厂家对样品的最小尺寸/质量/厚度要求

总结：如果出现以下情况，可以认为检测目标是一致的，可以进行无损分析：

· 样品未着色或镀金，颜色与眼睛一致。

· 从结构和设计的角度来看，样品没有其他方面的不一致

· 薄涂层的顶层仅与一个基材分离，可用于分析，此设备使用已知基材进行校准

使用任何 XRF 设备时，如果目标设计允许，建议测试样品的多个部分。

仪器之间的任何统计上的重要差异都可能意味着存在不均匀性。如果重复实验的结果表明

如果测试材料不均匀，建议使用破坏性分析方法。

The matrix and interference effects of XRF energy dispersive X-ray fluorescence spectrometer

a) The scattering process of the excitation radiation will affect the characteristic radiation intensity of the elements in the sample. This is because the scattering process will affect the back of the spectrum.

view. In addition, there are two main effects:

b) The excitation radiation in the sample is absorbed and the resultant or fluorescent radiation emitted by other elements (matrix).

c) Secondary excitation (enhancement) of other elements in the sample.

— Plastic material: The matrix in the plastic sample will affect the characteristic X-ray intensity of the analyte, mainly from:

— Scattering of primary radiation (mainly discontinuous), which makes a great contribution to the background spectrum

— Absorption in fluorescent radiation, which is mainly caused by Cl in PVC, additive elements such as Ca, Ti, Zn, Sn, etc., and derived from

Br and Sb in flame retardants

— Secondary excitation caused by elements such as Sb, Sn, and Br

— Metal: Scattering caused by primary excitation in a metal sample does not play an important role. The matrix effect is mainly caused by absorption and secondary

These effects are not the same for different metal substrates. Some of the different substrates are listed below.

Typical elements:

— Fe alloy: Fe, Cr, Ni, Nb, Mo, W,…

— Al alloy: Al, Mg, Si, Cu, Zn,…

— Cu alloy: Cu, Zn, Sn, Pb, Mn, Ni, Co,…

— Solder alloys: Pb, Cu, Zn, Sn, Sb, Bi, Ag, ...

— Zn alloy: Zn, Al,…

— Precious metal alloys: Rh, Pd, Ag, Ir, Pt, Au, Cu, Zn,…

— Electronic components and printed circuit boards: In principle, all effects that occur in polymers and metals are included.

d) In addition, the intensity of the characteristic spectrum of the test element in the sample will be interfered by other elements. Typical interferences are as follows:

— Cadmium: possible interference comes from bromine, lead, tin, antimony

— Lead: possible interference comes from bromine

— Mercury: possible interference comes from bromine, lead, and high concentrations of calcium and iron in the sample

— Chromium: possible interference comes from chlorine

— Bromine: possible interference comes from iron and lead

e) The influence of matrix effect on the limit of detection (LOD)

Sample uniformity

The uniformity of XRF analysis points depends on the physical uniformity of the sample within the volume excited by the instrument. When testing samples

The following three items can be applied for uniformity.

a) Large surface samples (applicable to all samples): — It is obvious, necessary and useful to evaluate the uniformity of test samples for XRF analysis. For example, any in color.

Objects that are relatively uniform in shape and appearance do not need to be mechanically sampled before testing. Typical tests can be large and

Long plastic objects such as CRT monitoring boxes, plastic shells, thick belts, metal alloys, etc. Any additional information about the test object can be

To establish its uniformity, for example, many plastic and metal surfaces have coatings. Some plastic surfaces are metalized, test

The sample is wrapped inside. In this case, the sample needs to be disassembled to a certain extent, using uncoated or unmetallized plastic

To test. The metal surface may be plated with other metals, such as galvanized steel, cadmium-plated steel, chrome-plated steel, and chrome-plated aluminum. These are plated on

The metal of chrome will have a relatively high reading, and it may be a bit lower for chrome, because the chrome layer is usually very thin. If you want to analyze the base

Material, then all coatings should be removed.

b) Small surface samples:

— Small electronic components can also be considered uniform, as long as the analyte can be excited by the instrument and only the selected ones are analyzed

Locations, samples will also show uniformity, such as plastic encapsulation, separate solder or separate areas of polymer/epoxy.

When analyzing the substrate, take special care to avoid the interference of metal plating, polymer coating or paint. If there is a coating, it should be painted

The layer is physically removed.

c) Coating and thin samples:

— Samples that are too small or too thin are likely to cause loss of quality or thickness and result in unusable results. Test such small quality samples

(Such as small screws), put the sample in the sample cup. Similarly, when testing thin samples, stack the samples until they are thick.

Reach the minimum thickness required for the test, and then perform the routine test. The general rule is that all samples should completely cover the spectrum of the test

For windows, the minimum thickness for polymers and light metals such as Al, Mg or Ti is 5mm, the minimum thickness for liquids is 15mm, and the minimum for other alloys is 1mm. The insulation of thin wires and ribbon cables cannot be regarded as uniform, and the metal conductor must be removed before measurement. On the other hand, Any power cord with a copper core with a diameter greater than 5mm can be considered uniform. The metal can be measured after separation. 

The personnel knows that the structure of the material and the photometer can be calibrated to analyze such a complex surface structure, so some metal coatings can also be used.

To be analyzed. For example, the coating is already known to be SnAgCu (all gold plated) copper (all gold plated). Tin alloy can be used for analysis,

As long as the instrument can calibrate this type of sample. It is generally accepted that most XRF sensitive devices cannot be detected Into the conversion coating of Cr, unless the coating has a thickness of at least a few hundred nm. Because different instruments require different sizes of samples Change, it is recommended that the operator of the photometer consult the instrument manual or the manufacturer for the minimum size/quality/thickness requirements of the sample

Summary: The detection target can be considered to be consistent and non-destructive analysis can be performed if the following situations occur:

· The sample is not colored or gold-plated and the color is the same and consistent with the eyes.

· From the structure and design point of view, the sample is not otherwise inconsistent

· The top layer of the thin coating is separated from only one substrate and can be used for analysis, and this equipment is calibrated with a known substrate

When using any XRF equipment, it is recommended to test more than one part of the sample if the target design allows it. 

Any statistically important difference between instruments can mean that there is inhomogeneity. If the results of repeating the experiment show

If the test material is not uniform, it is recommended to use destructive analysis methods.