Ultrasonic-assisted drop-to-drop solvent microextraction in a capillary tube coupled with GC-FID for trace analysis of phthalate esters.

An easy-to-use, rapid, robust and inexpensive technique termed ultrasonic-assisted drop-to-drop solvent microextraction (USA-DDSME) in a capillary tube was used to extract trace phthalate esters in the dipping solution of plastic samples, followed by determination by using gas chromatography-flame ionization detection. Extraction conditions were optimized, including type and volume of extraction solvent, sample volume, extraction time and effect of salt concentration. The method showing the best extraction performance was used to obtain optimized conditions: 20 µL of solution sample; extraction solvent, 5.00 µL of dichloromethane; segments of extraction phase, five equal divisions; extraction time, 10 min; no added salt. The linearity of the method was determined by analyzing spiked water samples over a concentration range of 0.1-300 µg/L. All calibration curves were found to be linear, with correlation coefficients > 0.9965. The limit of detection was 0.02 µg/L. The recovery values were in the range of 68.91 to 124.8% and relative standard deviations were not higher than 14.2%. Thus, the USA-DDSME method is suitable for the extraction of trace phthalate esters in complicated samples.