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#241 Fluorescent X-Ray Analysis

Category : Environmental conservation
May27, 2016

Analyzing the harmful substances content is a requirement for products in order to pass the criteria defined in WEEE and RoHS Directive. From this volume, we will be introducing you instrumental analysis methods, including the fluorescent X-ray analysis, which is a popular method of simplified analysis, as well as the official methods of analysis, including the atomic absorption and ICP emission spectrometric analysis. Now, let's start with the fluorescent X-ray analysis.

(1) Measurement principle

Atoms comprising a substance have their unique core electron level. Emitting X-ray, γ-ray, or electron beam to this atom generates the X-ray with characteristics unique to that atom (so called "characteristic X-ray"). This X-ray is called fluorescent X-ray. The energy (wavelength) is known to correspond with difference of atom's core electron level, which is equal to the characteristic energy transferred between the atom shells.
The fluorescent X-ray analysis analyzes the type and volume of atoms present in a substance by using this fluorescent X-ray. The qualitative analysis identifies the type of atoms while the quantitative analysis measures the contained amount.

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(2) Characteristics

(1) Qualitative analysis

This method can identify impurity elements attached to or mixed into compounds, mixtures, and reagents and can easily perform analyses of elements such as rare-earth elements that are difficult for normal analyses.

(2) Quantitative analysis

In addition to the ratio by weight or molar ratio of the element, this method can measure coating thickness of plating and the weight of a trace substance.

(3) No use of reference sample

This analysis used to require a reference sample. However, adopting the fundamental parameter (FP) method has eliminated the need for reference samples in the analysis. The improvement of data processing abilities by PC and its lowered cost have made the integration of atom-specific energy database and FP method programs easier than ever. Therefore, if you know the composition information of a sample, it is possible to calculate the X-ray strength by inputting FP (physical constant or fundamental constant) along with the measurement conditions into the logical formula based on the generation principle of fluorescent X-ray. This calculation result can be used for identifying elements and analyzing the amount.

(4) No pretreatment required

Usual analytical methods require pretreatment processes, such as dissolving a sample into acid. However, with the fluorescent X-ray analysis, you can analyze samples in the solid state without performing such pretreatment process.

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