Heumann K G
Biomed Mass Spectrom. 1985 Sep;12(9):477-88. doi: 10.1002/bms.1200120906.
The main ionization methods in a mass spectrometer for isotope ratio determinations of the elements are discussed in this review. These methods are thermal ionization, spark source, electron impact, inductively coupled plasma and field desorption. As concerns thermal ionization, electron impact and field desorption, a survey of the possibilities of isotope analyses in the periodic table of the elements is given. Besides kinetic studies, trace element determination by isotope dilution technique is the main application for isotope ratio measurements of the elements. The definitive method, isotope dilution mass spectrometry, is discussed as a potential tool for achieving accurate and precise trace analyses. Using field desorption mass spectrometry, one example of calcium kinetics in man and one example of thallium trace determination in an animal tissue are given. Other metal trace analyses with the isotope dilution technique are presented for biological and medical samples using positive thermal ionization mass spectrometry. Negative thermal ions are formed for the mass spectrometric analysis of non-metals and non-metal compounds in food samples, e.g. for iodine and nitrate in milk powder. Preliminary results with the isotope dilution technique are presented for a new quadrupole thermal ionization mass spectrometer which is a low-cost instrument and can be easily handled.
本文综述了质谱仪中用于元素同位素比值测定的主要电离方法。这些方法包括热电离、火花源、电子轰击、电感耦合等离子体和场解吸。关于热电离、电子轰击和场解吸，给出了元素周期表中同位素分析可能性的概述。除动力学研究外，通过同位素稀释技术测定微量元素是元素同位素比值测量的主要应用。作为实现准确和精确痕量分析的潜在工具，对权威方法同位素稀释质谱法进行了讨论。利用场解吸质谱法，给出了人体中钙动力学的一个例子和动物组织中铊痕量测定的一个例子。使用正热电离质谱法对生物和医学样品进行了其他金属痕量分析，并采用同位素稀释技术。通过形成负热离子对食品样品中的非金属和非金属化合物进行质谱分析，例如对奶粉中的碘和硝酸盐进行分析。给出了一种新型四极热电离质谱仪的同位素稀释技术初步结果，该仪器成本低且易于操作。
