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-fo cusing Nier-Johnson analyser with laminated magnet and a novel variable dis persion ion optical arrangement, enabling all masses to be located in the c entre 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 wit h effective gains for each collector determined from the standards. In both cases the repetition of ph isotope measurement is competetive with the the rmal ionization mass spectrometry (TIMS) double-spike method. (Int J Mass S pectrom 181 (1998) 51-58) (C) 1998 Elsevier Science B.V.