Development of Solid Phase Microextraction Device Based on the Use of Pencil Lead Graphite Sorbent Modified with Nanomaterials for the Extraction of Trace Phthalate Esters

Abstract

This thesis aimed to develop miniaturized sample preparation techniques for the determination of phthalate esters. To achieve this goal, two sub-projects were carried out. The first sub-project is the preliminary study of the extraction of benzyl butyl phthalate (BBP) and di-2-ethylhexyl phthalate (DEHP) by a silver-incorporated polyaniline film pencil lead SPME fiber (Ag/PANI SPME fiber). This fiber was used to extract trace phthalate esters and thermally desorbed at an injection port of a gas chromatograph coupled with an electron capture detector (GC-ECD). Under the optimum conditions, linearities of the determination of two phthalate esters, BBP and DEHP, were in the range of 0.05-5.00 mg L-1 and 0.25-5.00 mg L-1 and limits of detection of 0.030 and 0.24 mg L1 were also obtained for BBP and DEHP, respectively. A high preconcentration factor and satisfactory recoveries were achieved. This study indicated that the developed polyaniline/pencil lead SPME fiber can be used to extract BBP and DEHP. In the second sub-project, based on the results obtained and the problem found from the first sub-project, the size of the pencil lead used was enlarged to increase the sample loading capacity and to improve the robustness and the portability of the extraction technique. A screw-based portable and simple solid phase microextraction device constructed with a 3D printer was developed. The scanning electron microscope revealed the porous structure of the electrodeposited Ag/PANI film, and X-ray diffraction confirmed the presence of silver in the porous polymer film. The fiber was used to extract trace quantities of phthalate esters. The compounds of interest were dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-2-ethylhexyl phthalate (DEHP). The extracted solution was identified and quantified by a gas chromatograph equipped with a flame ionization detector (GC-FID). Under the optimum conditions of the developed method, a good linearity was obtained in a concentration range from 5.0 to 1.0×103 μg L-1 for all five phthalate esters with limits of detection (LODs) of 4.41±0.91 μg L-1 for DMP, 3.98±0.92 μg L-1 for DEP, 3.65±0.74 μg L-1 for DBP, 4.91±0.52 μg L-1 for BBP and 4.25±0.66 μg L-1 for DEHP. The developed method provided good precision when tested with standard solutions (RSD < 5.5%, n=6) and real samples (RSD <3.4%, n=6). Good fiber-to-fiber reproducibility was also confirmed by extraction with six prepared fibers: recoveries ranged from 81.09±0.54% to 92.92±0.46%, RSD < 6.6% (n=6). The developed method was used to determine phthalate esters in 14 cosmeceutical samples. In rubbing alcohol, DEP and DEHP were detected at the concentrations of 7.03±0.76 μg L1 and 5.89±0.53 μg L-1, respectively, while in contact lens cleaner samples, DEHP was found in a concentration range from 5.3±1.1 μg L-1 to 6.8±1.2 μg L-1. No contamination was found in saline solution, eye cleaner and antibacterial disinfectant liquid samples. Recoveries in the range of 81.92±0.99% to 102.4±1.1% indicated the good accuracy of the developed method. It was expected that the developed method would also be applicable for the extraction and determination of other organic compounds.