Comparison of 27- and 40-MHz plasmas in inductively coupled plasma mass spectrometry
The analytical characteristics of a 27.12- and a 40.68-MHz inductively coupled plasma (ICP) are compared as ion sources for use in inductively coupled plasma mass spectrometry. The background spectra produced by the two sources are similar; however, there is evidence of greater entrainment of air in the higher frequency discharge. Calibration graphs are linear over 6–7 orders of magnitude with both operating frequencies, although the 40.68-MHz ICP suffers a factor of 2–5 loss in sensitivity. Accordingly, detection limits are also slightly worse at the higher operating frequency, as is the precision. Interference effects are independent of operating frequency, but the extent of doubly charged, oxide and hydroxide ion formation might be affected by a more significant orifice-linked discharge with the 40.68-MHz ICP.