Comparison of center-tapped and inverted load-coil geometries for inductively coupled plasma-mass spectrometry

A non-commercial inductively coupled plasma-mass spectrometry (ICP-MS) instrument is used to compare a center-tapped ICP load-coil geometry with the standard inverted-coil arrangement. This direct comparison on the same ICP-MS unit shows that the load coil exerts only a minor influence on analytical characteristics such as sensitivity, doubly charged ion and oxide-ion ratios, and detection limits. The influence of operating parameters (nebulizer flow rate, sampling depth, generator rf frequency and applied power) on analyte-ion signals and oxide-ion ratios similarly appears to be independent of the load coil. However, the load-coil geometry is found to dictate the particular nebulizer flow rate, sampling depth, and biaspotential setting that are optimal and how these parameters affect doubly charged ion ratios and backgroundion signal magnitudes. Also, there is a greater loss in sensitivity for higher-mass elements with the center-tapped unit.