Detection limit of elements

As discussed before, quadrupole based ICP-MS allows multi-element determination at the trace and ultratrace level and/or isotope ratios in aqueous solutions in a few minutes as a routine method with detection limits of elements in the sub pgml-1 range and a precision for determined trace element concentration in the low % range (RSD - relative standard deviation). The precision for isotope ratio measurements varies between 0.1% and 0.5% RSD. This isotope ratio precision is sufficient for a multitude of applications, e.g., for evidence of contamination of sample with depleted or enriched uranium in urine (this technique is used in the author s laboratory in a routine mode14) or the isotope dilution technique for the quantitative determination of trace element and species concentration after doping the sample with enriched isotope spikes. 

Investigations of cluster formation serve to explain the evaporation and atomization of sample material and ion formation processes. A further aim of cluster research is to find out under what conditions cluster or polyatomic ion formation can be influenced in order to avoid disturbing interferences and decrease the detection limits of elements. On the other hand, polyatomic ions have also been used as analyte ions for analysis, e.g. the application of MCs+ and MCs2+ dimeric and trimeric ions as analyte11 or of cluster primary ion beams (e.g., of bismuth and gold primary clusters)15 16 by the bombardment and sputtering of a solid surface in SIMS.17-21 Especially in SIMS, a multitude of cluster ions with high ion formation rates are observed.18 22 23... 

Table 1.3 Approximate detection limits of elements in selected spectrometric methods...

Atom or molecule observed Compound used Wavelength of line or bandhead line or bandhead (nm) Detection limit of element without background correction ... 

Spectroscopic detection limits differ for different elements many elements can be detected at very low concentration levels, some as low as 10 g. The spectroscopist should become familiar with detection limits of elements of most concern in his particular field and under his excitation conditions. The sensitivity of qualitative spectral analysis is dependent on the type and size of the sample, the excitation conditions, and the sensitivity of the photographic emulsion and the optical system used with the spectrograph. For best results excitation conditions should be maintained as uniform as possible. 

XRF spectroscopy is a non-destructive and fast technique used for both qualitative and quantitative elemental analysis. This method has a fairly uniform detection limit of elements heavier than fluorine with a wide range of concentration, e.g. 100% to parts per million. 

Typical detection limit ranges for the major atomic spectroscopy techniques are listed in Table 7.2 which provides detection limits of element for five atomic spectroscopic techniques flame AA, mercury/hydride AA, GFAA, ICP emission, and ICP-MS. Interferences for these methods are listed in Table 7.3. 

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