| Total Reflection X-Ray Fluorescence(TXRF)is a highly sensitive multi-element analysis technology developed based on energy-dispersive X-ray fluorescence spectroscopy.The preparation process for solid samples is usually more complicated,and the repeatability and accuracy of the measurement results are poor.Especially for solid samples with complex physical structures and chemical components,the effectiveness is more difficult.This study focuses on the measurement of complex solid samples,starting from two aspects of optimizing sample preparation methods and improving sample injection methods,focusing on rapid TXRF analysis of plant samples rich in high organic matter and high salinity,high viscosity food samples.The main research content and research results are as follows:1)For the plant powder samples,by optimizing and improving the suspension preparation conditions and TXRF measurement parameters,a new suspension sample preparation method using a nonionic small molecule and nonionic macromolecular surfactant compound system as a dispersant was established.The research results show that for the plant powder sample,the compound system of 10% ethylene glycol monomethyl ether + 0.1% Triton X-100 was used as the dispersant,and the mass concentration range of the suspension was 5 mg/mL~25 mg/ mL,and then ultrasonic treatment 15 min,can obtain a good stability of the suspension,a single injection of 10 ?L,and a measurement of 2000 s can obtain a good TXRF measurement effect.In addition,for the problem of low measurement values of light elements(P,S,Cl,K,Ca)in plant samples,a plant standard sample close to the matrix of the sample to be tested was recalibrated and corrected for the light element sensitivity factor.The recovery rate of the light element from 21.9 to 88.7% was increased to 96.5% to 110.8%.The method performance evaluation test shows that the method precision was 0.2~8.1%,and the recovery rate was between 88.5%~110.8%.Finally,the suspension sample preparation method of the compound system was compared with the commonly used autoclave closed digestion method.The results showed that they have equivalent quantitative accuracy for the tobacco leaf sample TXRF,and the recovery rates were 90.0~110.0% and 80.0%~110.0%,respectively.However,compared with the digestion method,the compound system suspension sample preparation method could avoid the cumbersome digestion process,shorten the pretreatment time,and will be more suitable for rapid TXRF analysis of plant samples.2)For viscous semi-flow solid samples,the centrifugal spin coating technology was used in the TXRF sample preparation process,and through optimization studies on the sample mass concentration,dilution ratio,spin coating speed and other factors,finally,a new TXRF quantitative analysis method based on spin coating technology was established.Milk powder and seafood sauce were selected as the analysis objects.The microscopic morphology characterization showed that the surface of the sample obtained by spin coating was uniform and regular,while the spot morphology formed by the conventional drop method has obvious local aggregation.The micro-region XRF element distribution test showed that the element distribution in the spot formed by the drop method showed a phenomenon of intermediate aggregation and weakening around the edge,but by the spin coating method was uniform and the aggregation phenomenon was not obvious.Speckle thickness test showed that the spin coating method could effectively reduce the thickness of the deposited spot.For the seafood sauce sample,the average thickness of the spot formed by the spin coating method was 21 ?m,and by the drop addition method was 91 ?m;The TXRF analysis results showed that the repeatability,accuracy and detection limit of the spin coating method was generally better than the conventional drop method,the recovery rate was 80%~ 110%,and the RSD <10%,especially the recovery rate of light element P,K and Ca in milk powder samples increased by 29%~67%,and the RSD value decreased from 19% to 6.5%.The TXRF test results of the spin-coated seafood sauce samples showed that trace elements Ca,Mn,Fe,Ni,Cu,Zn,Rb,Sr recovery rate was between 81.0% ~ 105.0%,RSD <8.0%,and compared with the drop addition method,the recovery rates of the light elements P,K and Ca in the seafood sauce were increased by 40% to 68%,and the RSD was reduced from 18% to 9.5%.TXRF quantitative analysis method established in this paper could be effectively applied to the accurate determination of multiple elements in food samples containing a viscous matrix. |
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