Method for Purification of Chlorine Isotope Samples in Groundwater Using Automatic Fraction Collection and Method Effectiveness Evaluation

High-quality purification and high-efficient recovery of the target is crucial in measuring isotope ratio by mass spectrometry to avoid potential interferences from matrix effects and data distortion from insufficient recovery. In this study, a new purification method for non-traditional stable isotope sample was presented based on high-performance ion chromatograph with an automatic fraction collector. Automated processing was achieved by optimizing the fraction collection parameters, and high purity was achieved through the external water suppression. Sample recovery was accurately calculated through precise quantification of the injection volume. In subsequent precise assessment of sample purity was proceeded as well. Take chlorine as an example in this work, high-precision and rapid analysis of chlorine isotope was achieved by the pretreatment method coupled with thermal ionization mass spectrometry. The results showed that the method achieved efficient and rapid separation of the target element from other interfering ions with high purification efficiency and recoveries from 98% to 102%. Separation and purification of chlorine could be completed within 25 min. Compared with the traditional low-pressure chromatography resin method, this method was not only fast and efficient, but also enabled purification-collection visualization of each sample. This purification method could be automatically operated with less reagent, and had broad application prospects in isotope sample pretreatment.