Electrodeposited Terephthalic Acid/Layered Double Hydroxide Nanosheets Coating for In-Tube Solid Phase Microextraction of Phthalate Esters from Beverages

In this work, a CuCr-layered double hydroxide nanosheet intercalated with terephthalic acid (TPA/LDH) coating was introduced in the on-line in-tube solid phase microextraction (IT-SPME) method. The TPA/LDH coating has been successfully fabricated on the inner surface of a stainless steel tube by a facile two-electrode electrodeposition method. The characteristics of the sorbent were investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR) and the sorbent thickness was obtained by an optical microscope and it was about 40 micro meter. The TPA/LDH coating, compared to NO3-LDH coatings, exhibited enhanced extraction efficiency, long lifetime, good mechanical stability and a large specific surface area. The IT-SPME method followed by HPLC-UV was used for the extraction and preconcentration of some phthalate esters (PEs) such as dimethyl phthalate (DMP), dibutyl phthalate (DBP), diallyl phthalate (DAP) and diethyl-hexyl phthalate (DEHP). Several important factors affecting extraction efficiency such as effects of pH, salt concentration, extraction and desorption conditions, and alcohol effect were investigated and optimized. Under the optimal conditions, the response for PEs was linear in the concentration range from 0.005 to 1000 μg L-1 with coefficients of determination better than 0.9958 and the limits of detection (at S/N=3) were obtained in the range of 0.01 to 0.1 μg L-1. The inter- and intra-assay precisions (RSD%, n = 3) were in the range of 3.8-6.8% and 3.5-5.7%, respectively. Finally, the method was successfully applied for the determination of four phthalate esters in the difference beverage samples and good results were obtained.