Laser ablation–inductively coupled plasma mass spectrometry with a time-of-flight mass analyser

Abstract

Laser ablation has been employed for sample introduction into an ICP-time-of-flight (TOF) mass spectrometer. The transients generated by the ablated material are generously sampled by the 10 kHz repetition rate of the TOF instrument. A detection limit of 10 ppb for Pb in a cast-iron standard is calculated from integration of a 0.3 s transient signal generated by a single laser pulse. By simultaneously acquiring and rationing the signals from two isotopes of Zn, the substantial pulse-to-pulse power fluctuations from the laser are virtually eliminated. Although some of the data are presented in a single- or double-channel acquisition mode, the results demonstrate the sensitivity and rationing abilities available for all elements and isotopes simultaneously from a single laser pulse. Use of a digital oscilloscope provides a full elemental spectrum for each laser pulse as the laser is rastered across a lava sample that contains plagioclase crystals. The relative spatial distributions for 11 elements of interest contained in this sample are plotted over an 11 mm distance. This paper is not intended to be a display of state-of-the-art laser-ablation techniques, as the large beam divergence of the ruby laser limits the spatial resolution to 1 mm. However, the ability of the plasma-source TOF mass spectrometer for analysing transient signals is clearly demonstrated.