Evaluation of space charge effects in the second vacuum stage of a commercial inductively coupled plasma mass spectrometer by planar laser-induced fluorescence imaging

The effect of matrix on the formation and focusing of a Ca ion beam in the second vacuum stage of an inductively coupled plasma mass spectrometer has been evaluated with the use of planar laser induced fluorescence. A cross section of the beam was imaged near the entrance to the mass analyzer of a commercial instrument. Characteristics of the beam from a solution containing only the Ca analyte closely matched those predicted by simulation software. The individual addition of three matrix species, Mg, Cs, and Pb, had minor effect on beam shape. Cs and Pb both affected the beam trajectory. The most pronounced effect was with the Pb matrix, which caused an order-of-magnitude drop in the Ca signal intensity at the electron multiplier of the mass spectrometer. The loss in signal was due primarily to a shift in the direction and location of the Ca ion beam that caused it to miss the entrance into the mass analyzer. - Highlights: ► We image a Ca ion beam in the second vacuum stage of an ICP-MS using PLIF. ► Ion beam shape and size is accurately predicted by SIMION. ► Added matrix species do not dramatically change beam shape. ► Heavy matrix species change beam direction and position.