The Devolopment Of Natural Matrix Reference Materials For Mixed Inorganic Elements In Groundwater And Study Of Matrix Effect

The data quality of groundwater samples tested in the investigation of groundwater pollution determines the reliability and comparability of investigation.The reference material plays a vital role for the data quality.The composition of the reference material matrix is more similar to that of the samples to be tested in the testing process of gourdwater samples,the obtained data are more accurate and reliable.This study prepared natural matrix reference materials for groundwater of China,and we studied the matrix effect by using ICP-MS and FAAS during the samples testing process.We developed 3 mixed reference materials for natural matrix inorganic elements in groundwater,and verified the calibration effects of the prepared reference materials.The main results are as follows:1.The signal intensity of Cd,Cu,Zn,Mn decreased 32.7%,28.6%,32.8%,and 26.3%,respectively with the increased Ca concentration(from 0 to 900 mg/L)during the ICP-MS measurement process.With the increased Na concentration,the signal intensity of Cd,Cu,Zn decreased 16.2%,20.7%,and 15.5%,respectively but the signal intensity of Mn increased 7.9%.Quantitative analysis of Cd,Cu,Zn,and Mn is seriously interfered by both Na and Ca matrix elements,and Ca has stronger interference effect for 4 elements.2.During the FAAS measurement process,the tested minimum value of Cu(1,5,10,and 20 mg/L)with the addition of Na matrix solution,decreased 3.20%,4.80%,7.00%,and 7.50%,respectively,compared with that of Cu without Na matrix solution addition.While,the tested minimum value of Cu with the addition of Ca matrix solution,decreased 12.7%,9.00%,7.30%,and 9.00%,respectively,compared with that of Cu without Ca matrix solution addition.The tested minimum value of Mn(four differnt concentrations)with the addition of Na matrix solution,decreased 26.6%,21.6%,31.8%,and 43.5%,respectively,compared with that of Mn without Na matrix solution addition.The tested minimum value of Mn(four differnt concentrations)with the addition of Ca matrix solution,decreased 23.5%,17.8%,8.70%,and 28.5%,respectively,compared with that of Mn without Ca matrix solution addition.The measurement of Cu and Mn was greatly influenced by Na and Ca matrix.However,the measurement of Cd and Zn had little influence.3.Based on rule of national primary reference material and ISO guideline 35: reference materials-general and statistical principles for certification,we developed 3 mixed reference materials for natural matrix inorganic elements in groundwater.Results indicated that the tested homogeneity and stability for fifteen elements in reference material are acceptable.The testing method is correct and the test data are reliable.4.Calibration effect of prepared natural matrix reference materials,single element reference material with non-natural matrix and mixed elements reference material with non-natural matrix are verified and compared.Results show that only 3 values tested by prepared standard curves can accurately reproduce the results of Cd,Cu,Pb in the European Union standard material BCR-09 and BCR-10,while another two results tested by prepared standard curves just can reproduce the results of partial elements.The composition of the natural matrix reference material is more similar to that of the samples to be tested,the beter calibration effect will be obtained.