A new variable dispersion double-focusing plasma mass spectrometer with performance illustrated for Pb isotopes

A new generation multiple collector plasma source mass spectrometer (PSMS) produced by Nu Instruments Ltd is evaluated. The instrument has a double-focusing Nier-Johnson analyser with laminated magnet and a novel variable dispersion ion optical arrangement, enabling all masses to be located in the centre of the Faraday collectors of a fixed static array. The performance of the instrument has been assessed through the analysis of NBS-981 Pb using a Tl doping technique with Faraday collector efficiencies and amplifier gains determined independently. A second method of analysis involves comparison of interspersed standard and sample ph measurements with effective gains for each collector determined from the standards. In both cases the repetition of ph isotope measurement is competetive with the thermal ionization mass spectrometry (TIMS) double-spike method. (Int J Mass Spectrom 181 (1998) 51-58) (C) 1998 Elsevier Science B.V.