PROGRESS IN THE ACCURACY ENHANCEMENT FOR ELEMENTAL ANALYSIS BY QUADRUPOLE-BASED PLASMA-SNMS

The elemental quantification in plasma-based SNMS is hampered by the m atrix dependence of the detection efficiencies. The signals of element s of unknown compounds can only be converted to concentrations with me an detection factors resulting in concentrations with an uncertainty m ainly given by the matrix effect. This situation can be considerably i mproved by energy measurements of the sputtered particles. The energy distribution (ED) can be used in two ways. First, the exact knowledge of the ED to each detected element allows an element specific integrat ion of the directly sputtered atoms eliminating thermal species from r esputtered wall deposition. For a set of copper compounds the spread o f the Cu detection factors could be reduced from +/- 63% for the conve ntional measurement to +/- 35% using energy resolved data. Second, the shape of the ED of postionised atoms differs considerably from all in terfering species, such as clusters as well as twice charged atoms whi ch could superimpose on the atomic signals. A quantitative shape analy sis of the measured ED was developed to correct for these interfering species. Examples are given for both superpositions with cluster inten sities and interferences with twice charged intensities. To reduce the additional time necessary to obtain the ED, the number of energy reso lved data points was reduced in steps down to 3 points only which stil l reduced a superposition error to half of the value without ED based correction.