GEMOC ARC National Key CentreGLITTER: On-line Interactive Data Reduction for the LA-ICPMS Microprobe
Esmé van Achterbergh1, Chris G. Ryan2 and William L. Griffin1,2
1. ARC National Key Centre for Geochemical Evolution
and Metallogeny of Continents (GEMOC), Macquarie University, NSW 2109,
Australia
2. CSIRO Exploration and Mining, P.O. Box 136, North
Ryde, NSW 2113, Australia
Laser ablation ICP-MS has become a routine tool in the determination of trace element abundance in geological and other samples. However, up to now, data reduction software has been limited to off-line data analysis, which is often labour intensive and time-consuming. To harness the full power of the LAM microprobe, the user should be able to view the results of an analysis within seconds of data acquisition, and to use that input to guide further analytical strategy. To meet this need, GEMOC has now developed GLITTER, the GEMOC Laser ICPMS Total Trace Element Reduction software package. This new interactive program gives users of the laser ablation microprobe a unique analytical environment. It provides real-time on-line data reduction for the LAM-ICPMS and features linked graphics and analysis tables, greatly improving both productivity and the flexibility of analysis. A variety of plotting options allows the user to evaluate the quality and significance of each analysis during the run, and to change dynamically the focus of the session if required.
The first results are calculated as soon as one standard and one unknown sample have been analysed. With each additional standard analysis, the data are instantaneously adjusted to take account of changes in the analytical conditions. With the last analysis, all data are re-calculated using the best possible yield interpolation, and no off-line reprocessing is required, (but can be undertaken for specific purposes).
GLITTER runs compiled code in the IDL programming language, rather than macros in spreadsheet programs. This has the advantage of greatly increasing the speed of the calculation procedures (to the order of fractions of a second) and reducing disk storage requirements. The code is easily maintainable and expandable, and provides cross-platform support for a number of environments, including Microsoft Windows, MacOS, UNIX and VAX-VMS.
GLITTER consists of five main interactive user interfaces ("windows"):
2. The "Standards" window requires the user to input the identity and values of the internal standard
3. The "Review" window shows the time resolved laser signals and allows selection of integration intervals by the user. Two displays appear in "Review" containing the time-resolved signals of the current analysis. The upper display consists of rows of pixels, each representing the variation of the signal with time for a single isotope, with intensity shown by colour brightness. This gives an immediate and clearly visible indication of any spikes in the data, or heterogeneity in the samples, for one or more isotopes. The lower display shows the time-resolved signal for a single isotope, selected using a horizontal marker in the pixelmap display.
4. The "Options" window allows selection of the type of yield interpolation (cps/ppm) across the standard analyses (the average yield of all the standard analyses, or a linear, quadratic or cubic fit across the standard analyses is selectable from this window). Other options include control over the background fitting procedures and the magnitude of the error associated with the internal standard values.
5. The "Plot" window(s) shows data in various forms (chondrite-normalised diagrams, X-Y scatter plots, run quality control diagrams etc.)
