Dispersive liquid–liquid microextraction followed by high performance liquid chromatography for determination of phthalic esters in environmental water samples

Abstract

A new method was developed for the simultaneous determination of six phthalic acid esters (PAEs) in different environmental water samples using salt-assisted dispersive liquid–liquid microextraction with carbon tetrachloride as an extraction solvent and acetonitrile as a dispersive solvent coupled with high performance liquid chromatography with UV detection. The influence of the added NaCl on the enrichment factor (EF) in DLLME was investigated. The salting-out effect causes the hydrophobicity of organic analytes to be increased and high EFs to be more pronounced than those in salt-free water. Greater EF, wider linearity, better recovery, smaller relative standard deviation (RSD) and lower limit of detection were obtained at higher concentration of NaCl. Under optimized extraction conditions, good linearity was observed for all analytes in a range of 1.00–100 μg L⁻¹ with the correlation coefficient (r²) ≥0.9992. The limits of detection based on the signal to noise ratio of 3 were 0.01–0.03 μg L⁻¹. The recoveries of PAEs were 97.5–105.5% for spiked water with 20 μg L⁻¹ of PAEs. The repeatability of the proposed method expressed as RSDs ranged from 3.13 to 5.32% (n = 3). EFs are in the range of 78 to 262 fold. The method was applied to the determination of PAEs in water samples from local river, rain and urban wastewater treatment plants with the standard addition, the recoveries of PAEs were 86.2–105.0%, 93.8–107.0% and 92.4–106.3%, and the RSDs were below 6.79%. The current procedure afforded a convenient, inexpensive and reliable sample preparation with high extraction efficiency for trace PAEs in environmental water samples.