XRF能量色散X射線熒光光譜儀的基質基體干涉效應分析

a) 激發(fā)輻射的散射過程會影響樣品中元素的特征輻射強度。這是因為散射過程會影響光譜的背面。

看法。此外，還有兩個主要影響：

b) 樣品中的激發(fā)輻射被吸收，其他元素（基質）發(fā)出由此產生的或熒光輻射。

c) 樣品中其他元素的二次激發(fā)（增強）。

— 塑料材料：塑料樣品中的基質會影響分析物的特征 X 射線強度，主要來自：

— 一次輻射的散射（主要是不連續(xù)的），這對背景光譜有很大的貢獻

— 在熒光輻射中的吸收，主要是由 PVC 中的 Cl、Ca、Ti、Zn、Sn 等添加元素引起的，來源于

阻燃劑中的溴和銻

— 由 Sb、Sn 和 Br 等元素引起的二次激發(fā)

— 金屬：金屬樣品中由初級激發(fā)引起的散射不起重要作用?；|效應主要是由吸收和次要引起的

對于不同的金屬基材，這些效果是不一樣的。下面列出了一些不同的基材。

典型元素：

— 鐵合金：Fe, Cr, Ni, Nb, Mo, W,...

— 鋁合金：Al、Mg、Si、Cu、Zn、...

— 銅合金：Cu、Zn、Sn、Pb、Mn、Ni、Co、...

— 焊料合金：Pb、Cu、Zn、Sn、Sb、Bi、Ag、...

— 鋅合金：鋅、鋁、…

— 貴金屬合金：Rh、Pd、Ag、Ir、Pt、Au、Cu、Zn……

— 電子元件和印刷電路板：原則上，包括在聚合物和金屬中發(fā)生的所有影響。

d) 此外，樣品中測試元素的特征光譜強度會受到其他元素的干擾。典型的干擾如下：

— 鎘：可能的干擾來自溴、鉛、錫、銻

— 鉛：可能的干擾來自溴

— 汞：可能的干擾來自樣品中的溴、鉛以及高濃度的鈣和鐵

— 鉻：可能的干擾來自氯

— 溴：可能的干擾來自鐵和鉛

e) 基質效應對檢測限（LOD）的影響

樣品均勻度

XRF 分析點的均勻性取決于樣品在儀器激發(fā)的體積內的物理均勻性。測試樣品時

可以應用以下三項來實現(xiàn)均勻性。

a) 大表面樣品（適用于所有樣品）： — 評估用于 XRF 分析的測試樣品的均勻性是顯而易見的、必要的和有用的。例如，任何顏色。

形狀和外觀相對統(tǒng)一的物體在測試前不需要進行機械采樣。典型的測試可能很大而且

長塑料物體，如 CRT 監(jiān)測盒、塑料外殼、厚帶、金屬合金等。關于測試物體的任何附加信息都可以

例如，為了建立其均勻性，許多塑料和金屬表面都有涂層。一些塑料表面被金屬化，測試

樣品被包裹在里面。在這種情況下，樣品需要進行一定程度的拆卸，使用未涂層或未金屬化的塑料

去測試。金屬表面可以鍍其他金屬，如鍍鋅鋼、鍍鎘鋼、鍍鉻鋼和鍍鉻鋁。這些鍍在

鉻的金屬會有比較高的讀數(shù)，鉻的可能低一點，因為鉻層通常很薄。如果要分析基數(shù)

材料，則應去除所有涂層。

b) 小表面樣品：

— 小的電子元件也可以被認為是統(tǒng)一的，只要分析物可以被儀器激發(fā)并且只分析選定的那些

位置、樣品也將顯示均勻性，例如塑料封裝、單獨的焊料或聚合物/環(huán)氧樹脂的單獨區(qū)域。

在分析基材時，要特別注意避免金屬鍍層、聚合物涂層或油漆的干擾。如果有涂層，則應涂漆

該層被物理移除。

c) 涂層和薄樣品：

— 樣品太小或太薄都可能導致質量或厚度下降，導致結果無法使用。測試這么小的質量樣本

（如小螺絲），將樣品放入樣品杯中。同樣，在測試薄樣品時，將樣品堆疊至厚。

達到測試所需的最小厚度，然后進行常規(guī)測試。一般規(guī)則是所有樣品都應*覆蓋測試的光譜

對于窗戶，聚合物和輕金屬（例如鋁、鎂或鈦）的最小厚度為 5mm，液體的最小厚度為 15mm，其他合金的最小厚度為 1mm。細線和帶狀電纜的絕緣不能算是均勻的，金屬導體必須是

測量前完成。另一方面，任何銅芯直徑大于5mm的電源線都可以認為是統(tǒng)一的。金屬可以在分離后進行測量。

工作人員知道，可以通過校準材料和光度計的結構來分析如此復雜的表面結構，因此也可以使用一些金屬涂層。

待分析。例如，已知涂層是 SnAgCu（全鍍金）銅（全鍍金）。錫合金可用于分析，

只要儀器可以校準這種類型的樣品。人們普遍認為，大多數(shù) XRF 敏感設備無法檢測到 Cr 轉化涂層，除非該涂層的厚度至少為幾百納米。由于不同的儀器需要不同尺寸的樣品變化，建議光度計的操作人員查閱儀器手冊或廠家對樣品的最小尺寸/質量/厚度要求

總結：如果出現(xiàn)以下情況，可以認為檢測目標是一致的，可以進行無損分析：

· 樣品未著色或鍍金，顏色與眼睛一致。

· 從結構和設計的角度來看，樣品沒有其他方面的不一致

· 薄涂層的頂層僅與一個基材分離，可用于分析，此設備使用已知基材進行校準

使用任何 XRF 設備時，如果目標設計允許，建議測試樣品的多個部分。

儀器之間的任何統(tǒng)計上的重要差異都可能意味著存在不均勻性。如果重復實驗的結果表明

如果測試材料不均勻，建議使用破壞性分析方法。

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.