What Are the Causes of Errors in FP Quantitative Results?

1. X-ray Fluorescence Analysis and Calibration Curve

X-ray fluorescence analysis has been used in various industries due to its ease of sample preparation, stability, and wide applicable concentration range. However, for quantitative analysis, influences such as secondary excitation and absorption among elements present in the sample occur, necessitating the use of a calibration curve with standard substances of the same matrix. Therefore, preparation of standard samples for each matrix is necessary, and if they are not commercially available, considerable effort is required, such as creating standards oneself.

2. FP Method

The FP method stands for the Fundamental Parameter Method, which is a technique for calculating theoretical X-ray intensity generated from samples with known composition based on physical constants.

3. FP Quantification and Errors

Using the FP method enables quantitative analysis of elements even without X-ray fluorescence standards and calibration curves necessary for each matrix in the past. Furthermore, by combining with automatic qualitative analysis, automatic qualitative and quantitative analysis becomes possible, greatly expanding the usage range of X-ray fluorescence.

However, to improve quantitative accuracy, there are several points to note. X-ray fluorescence analysis assumes the sample is in a completely uniform state for FP calculation, but for measurement samples where effects such as particle size and mineral effects occur due to sample preparation, it is better to add standard samples that cause similar effects or use preparation methods such as glass bead technique to obtain more accurate results. Furthermore, because calculations are theoretically carried out with a total of 100% by weight, appropriate information is needed for handling light elements such as carbon and oxygen, which have low quantitative accuracy in X-ray fluorescence. Generally, such light elements are entered as ‘balance’ (remaining) components in the composition formula, or corrective calculations are performed using scatter lines to address influences from light elements. For measurements of heavy elements within light elements, input of sample weight, area, and density is necessary as the X-ray escape depth becomes deeper. Moreover, corrections based on the material and thickness of the organic film used in the case of liquids or the loose powder method are also needed.

4. Example: Causes of Errors in FP Quantitative Results?

Mr. A, Mr. B, and Mr. C performed FP quantification of the same liquid sample using an X-ray fluorescence analyzer. After FP quantification calculations, a comparison of the quantitative results showed that Mr. A’s silicon and barium were close to the standard values. Mr. B’s barium was more than twice the standard value, and Mr. C’s silicon was more than twice the standard value.

Why did such differences in quantitative values occur?

FP quantitative results of the liquid sample

Hint: Mr. A correctly entered the correction parameters. The other two input errors were made regarding sample parameters.

5. JASIS 2024 New Technology Briefing

We’ve explained the causes of errors in FP quantification and solutions to eliminate these errors will be detailed at the upcoming JASIS new technology briefing. We welcome your attendance.

September 6, 2024, 11:00 AM – 11:30 AM, TKP (former APA) Venue Room No.2

“Is That Quantitative Value Really Correct? The Unseen Causes of Error in X-ray Fluorescence Quantitative Values and Their Solutions”