Supplementary Material of Ar peak normalization
Description
Applications such as radioactive element analysis of nuclear wastewater require TXRF online analysis. The commonly used internal standard method process is too cumbersome. The accuracy of the method using argon characteristic peak in air as normalization standard is tested. It is compared with external standard method and Compton scattering line normalization method. The calibration curve was established using Ga standard solution. The correlation coefficients between Ar peak normalization and external standard method were 0.99957. For Ca in solution, the correlation coefficients between the results for the Ar peak normalization and the results for Ga peak normalization were 0.997. The Ar peak and Compton scattering line peak at different incident angles were compared. At the angle of total reflection, the stability of the Ar peak are better than Compton scattering line peak. The theoretical basis for TXRF online analysis method based on Ar peak normalization is provided. In order to avoid potential residual elements in silicon wafers and sample containers, Ga, which exists sparsely in nature, was chosen as a standard element for verifying the feasibility of the Ar peak normalized external standard method. A 1 ppm Ga standard solution dissolved in 3% concentration HNO3 was used as the sample reagent for the experiment. In order to simulate the scenario that it is difficult to obtain the element to be tested for the sample to be tested, the adopted Ga standard solution was regarded as the sample to be tested obtained by sampling, and the accurate concentration was obtained by high-precision analysis in the laboratory. Due to the difficulty of obtaining standard samples with the same solvent and different concentrations, the experiments were based on the in situ enrichment method employed by Amedeo Cinosi et al[21]. whereby a small volume of solution is deposited and evaporated repeatedly, aiming at limiting the dispersion of the deposited droplets on the surface of the disc. By depositing the sample repeatedly over a small area of the sample reflector, different portions of the sample were deposited in similar areas to obtain the concentration of the element to be measured in the same volume of solution deposited at different multiples of the sample used. These samples were used to establish the relationship between the signal of the element to be measured in the sample and the Ar peak area, thus obtaining the sensitivity of the element to be measured relative to Ar for the same matrix. In order to compare the conditions applicable to the Ar peak and the normalization of the elemental scattering rays on the target surface of the X-ray tube, all tests were performed at an X-ray tube voltage of 35 KV and a tube current of 800 μA. The stable Ar peak is utilized in the case of difficulty in obtaining suitable scattering rays, and the quantitative analysis is carried out by Ar normalization drawing on the scattering ray normalization method.
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Steps to reproduce
The main devices of the apparatus include a side window X-ray tube (Mo target, 50 KV, 1 mA), a waveguide slit (10 × 30 × 0.06 mm), and a silicon drift detector (SDD, 30 mm2, 8 μm Be window, FHWM = 128 ± 3 eV @ 5.9 keV). The X-ray tube is fixed on a precision displacement stage by a fixture and is mounted on a precision tilting stage by a The X-ray tube was mounted on the precision displacement stage through clamps and on the precision tilt stage using right-angle fixing blocks. The height and inclination of the X-ray tube are adjusted by means of a precision displacement stage and a precision tilt stage. The waveguide structure is mounted on the precision tilt stage to correct for small angles due to processing errors, and the slit is constructed by two silicon wafers with a roughness of less than 0.5 nm and an aluminum foil in the middle. A silicon wafer with a surface roughness of less than 0.5 nm was used as the sample reflector for the test, and the X-ray incidence angle was adjusted using the precision tilt stage, with the silicon drift detector probe aligned with the center of the precision tilt stage. During the tests, the protective ring of the probe was very close to the sample, and the Be window was less than 3 mm from the sample. Due to the distance of the X-ray tube from the probe, the best detection limit of 149 pg (in 10 μL of a 1 mg- L-1 single-element Ga standard solution) was obtained for 1000 s of Ga testing at a tube voltage of 35 KV and a tube current of 800 μA. All tests were performed in an air atmosphere. In order to avoid potential residual elements in silicon wafers and sample containers, Ga, which exists sparsely in nature, was chosen as a standard element for verifying the feasibility of the Ar peak normalized external standard method. A 1 ppm Ga standard solution dissolved in 3% concentration HNO3 was used as the sample reagent for the experiment. The adopted Ga standard solution was regarded as the sample to be tested obtained by sampling, and the accurate concentration was obtained by high-precision analysis in the laboratory. Due to the difficulty of obtaining standard samples with the same solvent and different concentrations, the experiments were based on the in situ enrichment method whereby a small volume of solution is deposited and evaporated repeatedly, aiming at limiting the dispersion of the deposited droplets on the surface of the disc. By depositing the sample repeatedly over a small area of the sample reflector, different portions of the sample were deposited in similar areas to obtain the concentration of the element to be measured in the same volume of solution deposited at different multiples of the sample used. These samples were used to establish the relationship between the signal of the element to be measured in the sample and the Ar peak area, thus obtaining the sensitivity of the element to be measured relative to Ar for the same matrix.