Determination of mono- and dinitrotoluene isomers in contaminated real petrohemial wastewaters using ethylenedichloride (EDC)-based dispersive liquid-liquid microextractioncombined with gas chromatography-flame ionization detection

This paper describes adispersive liquid-liquid microextraction (DLLME), using 1,2-dichloroethane (EDC) as extractionsolvent associated with gas chromatography-flame ionization detector (GC-FID) for determination of traces of 2-nitrotoluene (2-NT), 3-nitrotoluene (3-NT), 4-nitrotoluene (4-NT), 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) in an aqueous medium. In this analytical procedure, asuitable mixture of extraction solvent (EDC) and dispersive solvent (methanol) was rapidly injected into aqueous samples. This process caused the formation of cloudy solution,which consisted of dispersed fine droplets of extraction solvent and aqueous phase. After centrifugation of the cloudy solution, the fine droplets of extraction solvent sedimented in the tail end of the conical test tube and then 0.2 μLof the sedimented phase was injected to GC-FID, using N2 as carrier gas. The effects of pH, volume of extraction/dispersive solvent, extraction time, and ionic strength were investigated in order to optimize the methodology. Nitrobenzene was used as internal standard for quantification .The limits of detection were 0.32, 0.27, 0.37, 0.95and 0.89μg L-1 for 2-NT, 3-NT, 4-NT, 2,4-DNT and 2,6-DNT, respectively. The relative standard deviation (RSD) and preconcentration factors (PF) of all compounds were obtained about 6% and 300, respectively. Finally, performance of the proposed method was evaluated for preconcentration and determination of nitrotoluenecompounds in natural water and petrochemical wastewater samples.

Keywords:

Dispersive liquid–liquid microextraction , nitrotoluene , 1 , 2-dichloroethane , petrochemical wastewaters