New subcritical fluid nebulizer (ScFN) for improving the determination of inorganic tin in gunshot residues by flame furnace-atomic absorption spectrometry

Franco Cid, Pia Kochifas, Héctor D. Mansilla, Paola Santander, Jorge Yañez S. and Dulasiri Amarasiriwardena
MICROCHEMICAL JOURNAL 125 (2015)

ABSTRACT

The determination of tin by FAAS is widely recognized as a difficult task in atomic spectrometry because of low sensitivity, poor detection limits and important interferences. In this work a new sample introduction system, the subcritical fluid nebulizer (ScFN) combined with the flame furnace-atomic absorption spectrometry (FF-AAS) was applied for improving the determination of inorganic tin in aqueous solutions. Online preconcentration of tin as Sn-PDC complex was carried out in a HPLC-guard cartridge (5 mm length, 2 mm diameter) filled with C-18 coated monolithic silica having an absorption capacity of 2.5 μg of tin. For preconcentration optimized conditions were achieved at 0.015% (m/v) of APDC and pH 5 obtaining a preconcentration factor of 17 using 2.5 mL of sample volume. The elution was done by means of subcritical liquid carbon dioxide and methanol with a flow rate of 1.5 L min− 1 which was directly introduced as a dry aerosol into the flame furnace where tin complexes are vaporized and atomized. Applying ScFN-FF-AAS the detection and quantification limits for tin in water were 0.008 mg L− 1 and 0.024 mg L− 1, respectively, increasing the power of detection in 325 times compared to the conventional detection limits obtained by flame atomic absorption spectrometry. The precision at 1 mg L− 1 was 1.5% expressed as RSD (N = 10). Tin was determined in samples of gunshot residues generated by firing four ammunition brands. The concentrations fluctuated between 52 and 151 μg L− 1.

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