Layered Double Hydroxides as a Coating for the Determination of Phthalate Esters in Aqueous Solution with Solid-Phase Microextraction Followed by Gas Chromatography

In this study, magnesium/aluminum-layered double hydroxide (Mg/Al-LDH) was prepared with the hydrothermal method and the morphological features of Mg/Al-LDH were characterized. The as-prepared Mg/Al-LDH was employed as a coating material and coated on the stainless steel wire to construct a solid-phase microextraction fiber. To evaluate the extraction performance of the fiber, four phthalate esters including benzyl butyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate and bis (2-ethylhexyl) phthalate were selected as model compounds. Several experimental parameters affecting the extraction efficiency, such as extraction temperature, extraction time and ionic strength, were optimized. Under the optimum conditions, linear ranges of 1-400 mu g L-1 for di-n-butyl phthalate, 10-500 mu g L-1 for di-n-octyl phthalate and 10-400 mu g L-1 for two other compounds were observed. The limits of detection and limits of quantification ranged from 0.24 to 2.31 mu g L-1 and 0.81 to 7.69 mu g L-1, respectively. The intra-day and inter-day precision are less than 15.3 and 8.7%. The relative standard deviation of fiber to fiber reproducibility ranged from 8.3 to 16.7%. Finally, the established method was satisfactorily applied to the determination of phthalate esters in the Yangtze River water samples and the recoveries were 76.1-110.6%.