Abstract:In recent years, with the development of multi receiver inductively coupled plasma mass spectrometry (MC-ICP-MS) and chemical separation and purification technology, thallium (TL) isotopes have been widely used in Paleoclimate evolution and environmental pollution source tracing, and gradually become one of the current research hotspots of metal stable isotope geochemistry. At present, manganese nodule powder (NOD-P-1, NOD-A-1) is the main reference material used to measure the accuracy and accuracy of thallium isotope testing in soil samples when thallium isotope is used to carry out soil pollution traceability research. However, the content of thallium in soil is significantly different from that in manganese nodules (for example, the content of thallium in manganese nodules is greater than 80 μg/g, and the content of thallium in most soils is lower, less than 10 μg/g). Therefore, it is not suitable to select manganese nodule powder standard sample to monitor the data quality when carrying out thallium isotope test of soil samples. In this study, three national soil reference materials (GBW07564, GBW07980, GBW07406a) were digested by microwave digestion, and thallium was chemically separated and purified by AG 1x8 200-400 mesh resin. The yield of thallium was greater than or equal to 94%, and the Tl blank in the whole process was less than 2 ng. When using MC-ICP-MS to test thallium isotopes, the internal standard method, standard sample standard cross method and Baxter formula are used to correct the quality discrimination effect in the process of instrument testing. In this study, the internal accuracy of ?205Tl997 is better than ± 0.32 ? (n=48, 2sd). The thallium isotopic compositions of GBW07564, GBW07980 and GBW07406a were -1.75 ? ± 0.20 ? (n=9, 2SD), -0.57 ? ± 0.24 ? (n=9, 2SD) and 4.27 ? ± 0.16 ? (n=9, 2SD), respectively, ranging from -1.8 ?~4.3 ?, which was roughly the range of known thallium isotopic ratios in soil (-2.5 ?~+8.5 ?). The three soil reference materials selected in this study have uniform chemical composition and stable thallium isotope composition, which are suitable for monitoring the reliability of soil thallium isotope analysis.