The corresponding mass spectra are shown in Figure 7. With
a compensation voltage of −22.5 Vc, the peak mass spectrum for the rubidium is marked by the higher abundance isotope m/
z 84.90 and residual acetonitrile clusters at m/z 125.92 and
166.94. At the compensation voltage of −17 Vc, the mass
spectrum is dominated by up to six acetonitrile adducts for the
doubly charged Sr2+ ion (m/z 167.01). Filtration of the Rb+
signal in this spectrum at −17 Vc relative to peak rubidium
intensity at −22.5 Vc suggests that the DMS suppresses 90% of
the Rb+ signal (10% transmission). Neither peak spectra
demonstrate the survival of water adducts at this fragmentor
voltage of 325 V, though the acetonitrile adducts are clearly
preserved. While the relative dispersion follows that of the
cesium system, the separation is clearly better for the strontium
target compared to the cesium target and begs more rigorous
investigation of DMS using acetonitrile solvation.