Improved preconcentration workflow for organic explosive traces in aqueous samples using solvent-assisted dispersive solid-phase extraction.

The present study deals with the development of a solvent-assisted dispersive solid phase extraction method for the extraction of HMX, RDX, and TNT from aqueous samples. Benzophenone and methanol were selected as explosives sorbent and dispersive solvent respectively. Extraction parameters like pH, extraction time, amount of sorbent, volume and type of the disperser solvent and centrifuge time were optimized. Dispersion of 0.5 mL dispersive solution (4% (w/v) benzophenone in methanol) was performed by injection into the 5 mL aqueous sample (pH=7) using a 1.0 mL syringe. After centrifuge, the extracted explosives were analyzed by high performance liquid chromatography with ultraviolet detection (HPLC-Uv). The results indicated that the linear ranges with the correlation coefficients of 0.99 ≤ R2 were 1.6-204.6 μg L-1, 1.4-213.7 μg L-1 and 1.3-225.9 μg L-1 for HMX, RDX and TNT respectively. The limit of detection and limit of quantification obtained for each explosive were: 0.3 μg L-1 and 0.8 μg L-1 for HMX, 0.3 μg L-1 and 0.9 μg L-1 for RDX and 0.2 μg L-1 and 0.7 μg L-1 for TNT. Finally, the practical applicability of the developed method was evaluated for the extraction of some organic explosives in water samples followed their determination by HPLC-Uv.