Determination of Phthalate Esters in Water and Liquid Pharmaceutical Samples by Dispersive Liquid-Liquid Microextraction (DLLME) and Gas Chromatography with Flame Ionization Detection (GC-FID)

A method of dispersive liquid-liquid microextraction (DLLME) with gas chromatographic separation has been developed and applied for the determination of phthalate esters in water samples and liquid pharmaceuticals. The method allows the determination of various phthalate esters with different polarities, namely: dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, di(2-ethylhexyl) phthalate and di-n-octyl phthalate, with high values for the enrichment factors (370-390) and extraction recoveries (91-97%). Almost complete isolation of the phthalate esters from water samples was achieved by DLLME using chloroform as the extracting phase containing a minimum of 5-10% acetonitrile, isopropanol, or acetone as the disperser solvent and 10% sodium chloride as the salting-out agent. The results showed that increasing the amount of disperser solvent in the extracting phase leads to the growth in the phase polarity and thus improves the extractability of the polar analytes. The limits of detection determined for a signal-to-noise ratio equal to 3 were in the range from 1.0 to 1.6 mu g L-1 and the relative standard deviations for 10.0 mu g L-1 were below 9.7% (n = 3). The developed method demonstrates good repeatability and linearity and will be useful for the screening and quantitative determination of phthalate esters in various water samples and liquid pharmaceuticals.