Carbon sorbent reinforced hollow fiber membrane microextraction for determination of trace polar organic compounds

Abstract

This work presents a proof of concept that hollow fiber liquid phase microextraction reinforced with carbon nanomaterials would improve the extraction efficiency of small and relatively polar organic compounds. Several types of carbon sorbents such as graphite, graphene, carbon nanofiber were studied. In research I, the hollow fiber membrane reinforced with graphite was developed for liquid phase microextraction of trihalomethanes in water samples. Parameters affecting extraction efficiency including organic solvent as supported liquid membrane, amount of loaded graphite and extraction time were investigated and optimized. The working range of 0.2-120 µg L-1 was obtained in 10 min extraction with good linearity (R2 > 0.99). Limit of detections were in the range of 0.01-0.1 µg L-1 with enrichment factors of 40-71. The method offered comparative sensitivity to the conventional HF-LPME with significantly shortened extraction time indicating that the addition of graphite to the HF-LPME could improve the extraction efficiency. In addition, the carbon sorbent reinforced HF-LPME was developed and configured for in-line extraction coupled to a chromatographic system for automated analysis. In research II, carbon nanofiber reinforced HF-LPME was developed and configured for simultaneous in-line extraction and detection of nonsteroidal anti-inflammatory acidic drugs in urine samples. The hollow fiber extraction chamber was designed and fabricated by a 3D printer and connected to high performance liquid chromatographic system (HPLC) for simultaneous in-line extraction and determination. Parameters affecting extraction efficiency including organic solvent as supported liquid membrane, donor and acceptor condition, and analytical sequence of automatic extraction and HPLC determination were investigated and optimized. The analytical sequence of automatic extraction and HPLC determination provided total analysis time of 47 min and the sample throughput of 4 samples hr-1 was achieved. The limit of detections for the method were in the range from 1.6-5.6 µg L-1. The recoveries in real human urine samples were in the range of 97-105 % and relative standard deviations were between 0.3-4.6 %. The carbon sorbent reinforced HF-LPME can enhance the extraction efficiency resulting in higher enrichment factor and shorter extraction time, which offer an advantage towards in-line extraction and automation to achieve high sample throughput.