Detection and quantification of metals in organic materials by laser-SNMS with nonresonant multiphoton ionization

We have shown that the sensitive detection and in favorable cases the quant ification of metals in organic materials by laser-SNMS with nonresonant mul tiphoton ionization (NRMPI) is possible, As a model system, sputter-deposit ed submonolayer coverages of metals on polymer surfaces (polycarbonate, pol y(vinylidene chloride), polyimide) were investigated. By use of these sampl es, relative sensitivity factors and detection limits of several metals (Be , Cr, Mn, Fe, Co, Ni, Mi, W) were determined using laser-SNMS with NRMPI, T he relative sensitivity factors for this kind of sample show a high level o f agreement with those for metals sputtered from alloys. The detection limi ts (similar to 1 ppm of a monolayer) are almost the same as for inorganic m atrixes such as Si or GaAs. Laser-SNMS with NRMPI was also used for the det ermination of the elemental composition of the active centers of metallopro teins (namely, the purple acid phosphatases extracted from sweet potatoes a nd from red kidney beans). These results have shown the ability of laser-SN MS to detect metal atoms bound to organic macromolecules with an atom conce ntration as low as 1 ppm. In comparison to TOF-SIMS, laser-SNMS is more sen sitive for metal detection in organic matrixes, since the secondary ion yie lds observed for these matrixes are reduced compared to matrixes optimized for high secondary ion emission, such as, for example, highly oxidized surf aces.