Simultaneous Derivatization and Dispersive Liquid-Liquid Microextraction for Fatty Acid GC Determination in Water

Simultaneous derivatization and dispersive liquid-liquid microextraction technique for gas chromatographic determination of fatty acids in water samples is presented. One hundred microlitre of ethanol:pyridine (4:1) were added to 4 mL aqueous sample. Then a solution containing 0.960 mL of acetone (disperser solvent), 10 mu L of carbon tetrachloride (extraction solvent) and 30 mu L of ethyl chloroformate (derivatization reagent) were rapidly injected into the aqueous sample. After centrifugation, 1 mu L sedimented phase with the analytes was analyzed by gas chromatography. The effects of extraction solvent type, derivatization, extraction, and disperser solvents volume, extraction time were investigated. The calibration graphs were linear up to 10 mg L-1 for azelaic acid (R (2) = 0.998) and up to 1 mg L-1 for palmitic and stearic acids (R (2) = 0.997). The detection limits were 14.5, 0.67 and 1.06 mu g L-1 for azelaic, palmitic, and stearic acids, respectively. Repeatabilities of the results were acceptable with relative standard deviations (RSD) up to 13%. A possibility to apply the proposed method for fatty acids determination in tap, lake, sea, and river water was demonstrated.