Measurement of Tin Isotope Ratios by Laser Resonance Ionization Mass Spectrometry

A preliminary method based on the laser resonance ionization mass spectrometer (LRIMS) developed in the laboratory was established to determine tin isotope ratios. By measuring the auto. ionization spectrum of tin atoms, a three. color. three. photon resonance ionization scheme was confirmed, and the laser wavelengths of each excitation/ionization step were. lambda(1) = 286. 4 nm, lambda(2) = 811. 6 nm and lambda(3) = 823. 7 nm. More effective electrothermal atomization of tin was implemented by mixing the samples and grapheme oxide solution, and the total detection efficiency of 1 mu g of tin sample was above 3x10(-5), which was about 4.5 times as high as the method of directly dropping samples. A tin. antimony. tellurium mixture at a ratio of 1. 1. 1 (m/m) was prepared as a simulant sample, and the major tin isotope ratios in the sample were determined. Results showed that the isobaric interference from antimony and tellurium was effectively avoided, and the relative standard deviations for Sn-116/(120) Sn, Sn-117/(120) Sn, Sn-118/(120) Sn, Sn-119/(120) Sn were all better than 1%. This work indicated that LRIMS could effectively avoid the isobaric interference in the measurement of tin isotope ratios, and could be applied to measure the fission product (121)mSn and Sn-126 in the reactor spent fuel.