Isotope dilution and plasma source mass spectrometry: an optimal combination for high precision analysis of trace elements

Isotope dilution mass spectrometry is a highly sensitive method capable of high precision, and accuracy. Because chemical manipulations are carried ou t on a direct weight basis and mass spectrometric determinations involve on ly isotopic mass ratio measurements, this method is directly traceable to t he SI unit for amount of substance, the mole, and is therefore considered a s a primary (or definitive) method of analysis, intrinsically superior to c omparative calibration methods used in conventional instrumental analysis. By virtue of several major advantages, including direct liquid sampling at atmospheric pressure, large multi-element capability, high ionization effic iency, fast scanning capability and widespread availability compared to TIM S instruments, ICP-source quadrupole mass spectrometers greatly improve sam ple throughput, thereby allowing the isotope dilution method to be used mor e routinely. lit turn, because it alleviates the need for quantitative samp le handling, isotope dilution. makes separation of the analytes from matrix elements much easier. This enables the analyst to use advanced high effici ency sample introduction systems without resorting to large dilution factor s, or impairing the cleanliness of the interface and ion optics and the ove rall performance of the ICP-MS instrument.