Ion-sensitive plate

Figure 1 Schematic diagram of a Mattauch-Herzog geometry spark source mass spectrometer using an ion-sensitive plate detector.

Figure 2 Ion-sensitive plate detector showing the species produced by the SSMS analysis of a Y203 Eu203 mixture compacted with gold powder.

Due to the relative uniformity of ion formation by the RF spark (although its timing is erratic), the most widely used method of quantitation in SSMS is to assume equal sensitivity for all elements and to compare the signal for an individual element with that of the total number of ions recorded on the beam monitor. By empirically calibratii the number of ions necessary to produce a certain blackness on the plate detector, one can estimate the concentration. The signal detected must be corrected for isotopic abundance and the known mass response of the ion-sensitive plate. By this procedure to accuracies within a factor of 3 of the true value can be obtained without standards. 

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