Isotope ratio measurements on solution samples by mass spectrometry using an atmospheric pressure ion source

A new technique is described permitting direct mass spectrometry of aqueous solutions. A high temperature D.C. plasma is used as an ionization source, solution samples being introduced by an ultrasonic nebulizer. The plasma flame is sampled with a small orifice and the extracted ions directed through a quadrupole mass spectrometer. Transmitted ions are detected by ion counting techniques and the spectrum produced by scanning the mass analyzer displayed on a chart record or fed to a synchronous multichannel analyzer. This technique can be used to make isotope ratio measurement with a relative precision of the order of 0.5. The results obtained in the analysis of Pb and Sr isotopes in minerals are given