A new method based on scanning laser ablation and inductively coupled plasma-mass spectrometry (LA-ICPMS) for the detection and identification of gunshot residue (GSR) particles from firearms discharges has been developed. Tape lifts were used to collect inorganic residues from skin surfaces. The laser ablation pattern and ICPMS conditions were optimized for the detection of metals present in GSR, such as (121)Sb, (137)Ba, and (208)Pb. Other isotopes ((27)Al, (29)Si, (31)P, (33)S, (35)Cl, (39)K, (44)Ca, (57)Fe, (60)Ni, (63)Cu, (66)Zn, and (118)Sn) were monitored during the ICPMS analyses to obtain additional information to possibly classify the GSR particles as either characteristic of GSR or consistent with GSR. In experiments with real samples, different firearms, calibers, and ammunitions were used. The performed method evaluation confirms that the developed methodology can be used as an alternative to the standard scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) technique, with the significant advantage of drastically reducing the analysis time to less than 66 min.

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A series of hydroxyapatite pellets were produced to use as matrix-matched standards for LA-ICP-MS analysis of trace metals in the first dorsal spine of tuna fish species (albacore tuna, Thunnus alalunga, and Atlantic bluefin tuna, Thunnus thynnus). These structures are interesting because they present growth rings and therefore could potentially be used as indicators of environmental pollution. The produced standards containing twelve analytes (Mg, Al, V, Mn, Zn, As, Sr, Rb, Cd, Ba, Hg and Pb) were prepared by co-precipitation of hydroxyapatite from calcium nitrate tetrahydrate and ammonium dihydrogen phosphate. Once synthesized, the concentration of the analytes in the standards was carefully determined in the laboratory and recoveries for the analytes were calculated. The hydroxyapatite enriched standards were found to be homogeneous and provided a linear calibration (correlation coefficients were better than 0.991 for most of the analytes). The methodology was applied to the determination of trace element concentration profiles in cross-sections of tuna fish dorsal spines. Limits of detection were estimated between 1.4 ng g À1 for cadmium and 751 ng g À1 for aluminium. The measured values for Mg, Zn, Sr and Pb in pelletized SRM 1486 Bone Meal were in good agreement with certified reference values.

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