Increased extraction efficiency of acetonitrile/water mixtures for explosives determination in plant tissues

The standard extraction technique for analysis of explosives in dried soils for explosives analysis uses an 18 hour cooled sonication extraction in acetonitrile (ACN). In order to eliminate possible thermal degradation of explosive analytes during the drying step, water was allowed to act as a modifier for the acetonitrile extraction solvent in extraction of un-dried plant tissues resulted. The modified extraction solvent resulted in more efficient extraction of explosives analytes from these matrices compared to extractions in 100% ACN. In order to understand this increased extraction efficiency, extractions and analyses were performed on plant tissues that had been exposed to contaminated irrigation water with varied extraction solvents. Significant increases in extractability of explosives from plant tissues were noted with increasing water ratios. These observations were investigated using gravimetric, high performance liquid chromatographic, and environmental scanning electron microscopic analysis. The increased efficiency of water modified acetonitrile extraction solvents is explained by a secondary extraction effect.