Research And Application Of Solid-Solid Mixing Sample Preparation-standard Addition Method In Determination Of Powder Samples By LA-ICP-MS

Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)can be used for direct injection analysis of solid samples.Compared with solution injection of ICP-MS analysis,it has the following advantages: LA-ICP-MS needs less sample preparation steps;in the analysis process,less harmful reagents such as acids and alkalis are used;polyatomic ion interferences caused by H,O,N,Cl in the liquid are significantly reduced.However,only samples with a completely matrix-match standard samples can obtain more accurate results in LA-ICP-MS analysis because of matrix effect,which limits the wide application of this method in samples lack of matrix-match standard samples.In order to solve the influence of the matrix effect,a solid-solid mixing sample preparation-standard addition method was established,and this method was used in the analysis of powder samples by LA-ICP-MS.The main research contents are as follows:1.Establishment of solid-solid mixing sample preparation methodThe three precious metal elements content of Pt,Pd and Rh in automobile exhaust gas catalytic converters(referred to as automobile exhaust catalysts)are taken as the research objects.When determinate Pt,Pd and Rh in the samples of automobile exhaust catalysts produced by different manufacturers with cordierite as matrix,there is no regularity for intensity and content of Pt,Pd and Rh.In order to eliminate the influence of matrix effect,standard addition method was used in the experiment.Liquid-solid mixing sample preparation can be used as sample preparation of standard addition method.Standard solution was mixed with automobile exhaust catalyst samples,wait until solvent was volatilized,press the mixture into tablet.Elements distribution uniformity was poor on the surface of samples prepared by this method,and the standard sample added during the preparation process was lost,the accuracy of the addition cannot be guaranteed.In order to solve the uniformity and accuracy of sample preparation,a solid-solid mixing sample preparation method was established.Solid phase extraction technique was introduced into the sample preparation process.The solid phase extractant was used to quantitatively adsorb elements to be tested,and then the solid phase extractant was mixed with samples to be tested to prepare analysis samples,and a standard addition method series samples for LA-ICP-MS analysis were prepared.2.Feasibility of solid-solid mixing sample preparation standard addition methodComparing activated carbon and functionalized silica gel,it is found that 2,4-dimercapto-1,3,5-triazine functionalized silica gel(DMT silica gel)has the best adsorption ability on Pt,Pd and Rh and can be pressed into a flat tablet mixed with automobile exhaust catalyst sample.DMT silica gel was selected as Pt,Pd and Rh carrier and mixed with automobile exhaust catalyst sample to prepare the standard addition method analysis samples.DMT silica gel has a large adsorption capacity for Pt,Pd and Rh.By controlling the total amount of elements in the solutions,the adsorption capacity of these three elements by silica gel can generate a gradient.DMT silica gel adsorbed Pt,Pd and Rh was mixed with the automobile exhaust catalyst sample to prepare samples.Element distribution on the surface of prepared samples was relatively uniform,and the sample preparation has good repeatability.Therefore,the standard addition method of solid-solid mixing sample preparation is feasible in LAICP-MS analysis.3.Determination of Pt,Pd and Rh in automobile exhaust catalyst by solid-solid mixing sample preparation-standard additionBy optimizing the adsorption conditions of Pt,Pd and Rh on DMT silica gel,silica gel particles with a gradient in content of these three elements were prepared.Optimized the diameter and ratio of the silica gel particles and the catalyst sample,and prepared a series of LA-ICP-MS analysis standard addition method samples.Under the optimized laser parameters,measured values were consistent with certified values.Relative error of results was within 4.7%.The RSD of three repeated measurements is less than 4.7%,and the detection limit of Pt is 1.2?g/g,Pd is 7.7?g/g,Rh is 0.46?g/g.The method is applied to the actual samples test,and results were consistent with the analysis results of the standard method(solution method).This method can be used in the analysis of Pt,Pd and Rh in automobile exhaust catalysts.4.Determination of trace Cd in soil samples by solid-solid mixing sample preparation-standard addition-LA-ICP-MS methodThe limit of Cd in the soil is low.The matrix varies between different soil samples.Matrix effect has a great influence on determination of soil samples by LA-ICP-MS.It is hard to use matrix matching standard samples because of unknown matrix of soil samples.Solid-solid mixing sample preparation-standard addition method can be used in the determination of trace Cd,and eliminates the influence of matrix effect.In the experiment,Re was used as the internal standard element,and DMT silica gel was used as carrier of Cd and Re.Cd in CRMs for soil samples were measured,and the determined values were consistent with the certified values.5.Determination of Au in gold mineral samples by solid-solid mixing sample preparation-standard addition-LA-ICP-MS methodSolution methods are always adopted in the determination of Au in gold mineral samples,and the sample preparation steps are more complicated and require well trained operators.Gold mineral samples are natural samples,and the samples matrix of different origins are quite different.LA-ICP-MS can analyze samples with less sample preparation steps.By comparing different functionalized silica gels,Triamine silica gel was selected as the carrier of Au.Under the optimized laser parameters,relative error of Au with standard sample was 7.3%,and the RSD% of the measurement results repeated three times was 4.4%.In summary,this study proposes a solid-solid mixing sample preparation-standard addition method,and uses this method in the analysis of powder samples by LA-ICPMS.It provides a new idea and method for the application of LA-ICP-MS in element content analysis.