OPTIMIZATION OF THE MASS SCANNING RATE FOR THE DETERMINATION OF LEAD ISOTOPE RATIOS USING AN INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETER

High-speed motion pictures of a plasma and the noise-amplitude spectra of the emission signals enabled clarification that the inductively coupled plasma coupled with a mass spectrometer had a noise component at a frequency of 380 Hz under the experimental conditions used. In order to improve the precision of lead isotope ratio measurements the mass scanning rate was optimized. With an increase in the mass scanning rate, the precision of lead isotope ratio measurements was improved because the low frequency noises could be eliminated. However, the quadrupole mass analyser could not be operated at a speed that was sufficient to smooth out the audio frequency noise.