Distribution coefficients of phthalates between absorption fiber and water and its using in quantitative analysis

Solid-phase microextraction (SPME) employing absorption type fibers coupled to gas chromatography was used to extract phthalic acid esters from water samples. Distribution coefficients between water and polydimethylsiloxane (KfwPDMS) and polyacrylate (KfwPA) for these compounds were determined. To estimate the values of Kfw for compounds of the same class, which did not undergo experiments, it is proposed to use an empirical two-parameter equation in which various physico-chemical and structural characteristics weakly correlated with each other are used as descriptors. Kfw values calculated on the basis of correlation with distribution coefficients in other heterogeneous systems correspond to the values determined experimentally. Distribution coefficients in polyacrylate/water system were used for quantitative determination by SPME–GC–FID method of phthalates in raw and purified municipal wastes which come from a wastewater purifying plant in Białystok. Concentration of the four phthalates detected in the wastewater (di-n-propyl phthalate, diisobutyl phthalate, di-n-butyl phthalate and di-2-ethylhexyl phthalate) ranged from 1.5 to 50 μg/l. During a purification process, decomposition of phthalates with higher polarity is the fastest whereas that of di-2-ethylhexyl phthalate is the slowest.