Principles and Treatment Methods for Metal Isotopes Analysis

Abstract

BACKGROUND In the past twenty years, methods for metal isotopes analysis (iron, copper, zinc, magnesium, calcium, lithium, molybdenum, selenium, mercury, chromium, cadmium, alum, barium, titanium, etc.) have been established. The sample pretreatment during metal isotope analysis includes two processes: the digestion of the sample; and the separation and purification of the analyzed elements. In order to ensure the accuracy and precision of metal isotopes data, two general principles of sample treatment must be followed. Elements that may interfere with the isotope analysis of the analyzed elements should not be introduced into the analysis. The analyzed elements should not be lost during the experiment. OBJECTIVES In order to understand the pretreatment methods for metal isotope analysis. METHODS Common sample digestion methods and chemical separation (ion exchange separation) were introduced in detail and were discussed in this paper. RESULTS The common sample digestion method for metal isotope analysis is the acid dissolution method (Teflon bombs and microwave digestion). The separation and purification of the element to be measured mainly uses the ion exchange separation method. The same resin can be used for the chemical separation of different elements, and the same element can also be chemically separated by using different resins. The matrices of different types of samples are quite different, and different processes are required to separate the analyzed elements. The separation requirements of different samples can be met by changing the separation process of the predecessors, including changing the resin or the amount, changing the eluent or the amount, and increasing the separation steps. CONCLUSIONS Based on the authors' experience, details should be paid attention to during treatments for metal isotope analysis: (1) HClO4 must be thoroughly removed at high temperature during sample digestion, because its strong oxidization can destroy the effectiveness of resins; (2) when the same volume of resin is put into the column, the thinner the column is, the slower the flow rate of the eluent, and the later elution of the elements to be measured; (3) the smaller the volume of the eluent added each time, the better the separation effect during ion exchange purification.

Keywords

• metal isotopes
• sample treatment
• digestion
• ion exchange separation