Dispersive liquid-liquid microextraction for the determination of nitrophenols in soils by microvial insert large volume injection-gas chromatography–mass spectrometry

• Six nitrophenol compounds were simultaneously determined in soils by GC–MS.
• Ultrasound assisted extraction in methanol is applied to isolate the analytes.
• UAE methanolic extracts were preconcentrated by DLLME in dichloromethane.
• Microvial insert large volume injection facilitated the GC injection.

A rapid and sensitive procedure for the determination of six NPs in soils by gas chromatography and mass spectrometry (GC–MS) is proposed. Ultrasound assisted extraction (UAE) is used for NP extraction from soil matrices to an organic solvent, while the environmentally friendly technique dispersive liquid-liquid microextraction (DLLME) is used for the preconcentration of the resulting UAE extracts. NPs were derivatized by applying an “in-situ” acetylation procedure, before being injected into the GC–MS system using microvial insert large volume injection (LVI). Several parameters affecting UAE, DLLME, derivatization and injection steps were investigated. The optimized procedure provided recoveries of 86–111% from spiked samples. Precision values of the procedure (expressed as relative standard deviation, RSD) lower than 12%, and limits of quantification ranging from 1.3 to 2.6 ng g−1, depending on the compound, were obtained. Twenty soil samples, obtained from military, industrial and agricultural areas, were analyzed by the proposed method. Two of the analytes were quantified in two of the samples obtained from industrial areas, at concentrations in the 4.8–9.6 ng g−1 range.