Application of Total Reflectance Fluorescence Analyzer (TXRF) in Soil Trace Heavy Metal Monitoring (1)

(1) Scope of application

Suitable for soil trace heavy metal analysis

(2) Method principle

After the sample is irradiated by X-rays, the inner shell (K, L, or M layer) electrons of each element atom are excited to drive out the atom, causing an electronic transition, and emitting the characteristic X-ray fluorescence of the element

(3) Instruments and equipment

The reference instrument is the TXRF0197-A total reflection X-ray fluorescence analyzer produced by Ewen Environmental Technology, which is mainly composed of three parts, namely the host, the computer and the high-purity nitrogen cylinder

Host containing the major functional modules, including power, X- ray tube, X- fluorescence detector, the total reflection optical platform, a driving circuit, piping and other nitrogen

Table 5-57 Total reflection X-ray fluorescence analyzer index parameters

(4) Sample preparation

The total reflection X-fluorescence analyzer has special requirements for the preparation method of the analysis sample, that is, the sample to be tested must be made into a thin film on a smooth slide; only when the thin film is tested, the total reflection effect will be produced, thereby effectively reducing the background Interference, to achieve a very low detection limit

(1) Sample preparation of solid sieve: The solid sample needs to be pulverized first, and the solid sample is pulverized to particles that can pass a 200-mesh sieve using a soil pulverizer

Put the prepared solid sample into a mixer and stir, the solid sample is fully suspended in the solution, and a 10uL sample is taken to make a film and dry it for testing

(2) Direct drip drying of water samples: This method is simple and fast to prepare the film, but the detection limit is slightly higher

Film making method: first drop a drop (10uL) of trimethylsilanol on a glass slide , dry it to form a hydrophobic film; drop 10uL sample on the hydrophobic film, dry it to form a sample film for TXRF testing

In order to improve the accuracy of sample detection, the blank value needs to be recalibrated before the daily low-mass concentration sample test

(3) The addition of internal standard elements

In terms of quantitative analysis, TXRF analysis is often easily affected by changes in film shape, position, size, uniformity, etc.

(4) Precautions for sample preparation: When the water sample is directly dripped and dried, in order to increase the detection limit of the sample, the method of enrichment and film preparation can be used in the film preparation process, that is, the method of drying in trimethylsilanol Titrate 10uL of the test sample on the hydrophobic film, and then titrate the 10uL sample after drying, and repeat the titration 3 times

The Hg element in the tested sample will be lost a lot with the increase of sample preparation temperature.

Related Links: Wavelength Dispersive X-ray Fluorescence Spectrometry of Soil and Sediment (3)