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Estimating Diphenylamine in Gunshot Residues from a New Tool for Identifying both Inorganic and Organic Residues in the Same Sample

1
MINTOTA Research Group, Departament de Química Analítica, Facultat de Química, Universitat de València, Dr. Moliner 50, Burjassot, 46100 Valencia, Spain
2
Institut de Ciència dels Materials (ICMUV), Universitat de València, P.O. Box 22085, 46071 Valencia, Spain
*
Author to whom correspondence should be addressed.
Separations 2019, 6(1), 16; https://doi.org/10.3390/separations6010016
Received: 10 January 2019 / Revised: 15 February 2019 / Accepted: 26 February 2019 / Published: 19 March 2019
(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)
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Abstract

A method involving the collection and determination of organic and inorganic gunshot residues on hands using on-line in-tube solid-phase microextraction (IT-SPME) coupled to miniaturized capillary liquid chromatography with diode array detection (CapLC-DAD) and scanning electron microscopy coupled to energy dispersion X-ray (SEM-EDX), respectively, for quantifying both residues was developed. The best extraction efficiency for diphenylamine (DPA) as the main target among organic residues was achieved by using a dry cotton swab followed by vortex-assisted extraction with water, which permits preservation of inorganic residues. Factors such as the nature and length of the IT-SPME extractive phase and volume of the sample processed were investigated and optimized to achieve high sensitivity: 90 cm of TRB-35 (35% diphenyl, 65% polydimethylsiloxane) capillary column and 1.8 mL of the processed sample were selected for the IT-SPME. Satisfactory limit of detection of the method for analysis of DPA deposited on shooters’ hands (0.3 ng) and precision (intra-day relative standard deviation, 9%) were obtained. The utility of the described approach was tested by analyzing several samples of shooters’ hands. Diphenylamine was found in 81% of the samples analyzed. Inorganic gunshot residues analyzed by SEM-EDX were also studied in cotton swab and lift tape kit samplers. Optical microscopy was used to see the inorganic gunshot residues in the cotton swab samplers. The lift tape kits provided lesser sensitivity for DPA than dry cotton swabs—around fourteen times. The possibility of environmental and occupational sources could be eliminated when DPA was found together with inorganic residues. Then, the presence of inorganic and organic residues in a given sample could be used as evidence in judicial proceedings in the forensic field. View Full-Text
Keywords: diphenylamine; gunshot residues; hands; dry cotton swab; in-tube solid-phase extraction; capillary liquid chromatography; SEM-EDX diphenylamine; gunshot residues; hands; dry cotton swab; in-tube solid-phase extraction; capillary liquid chromatography; SEM-EDX
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Argente-García, A.I.; Hakobyan, L.; Guillem, C.; Campíns-Falcó, P. Estimating Diphenylamine in Gunshot Residues from a New Tool for Identifying both Inorganic and Organic Residues in the Same Sample. Separations 2019, 6, 16.

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