Combining graphite with hollow-fiber liquid-phase microextraction for improving the extraction efficiency of relatively polar organic compounds

In this study, we have developed a simple and effective hybrid extraction method based on the incorporation of raw carbon nanosorbents and octanol in the pores of a hollow-fiber membrane for improving the extraction efficiency of relatively polar organic compounds. Trihalomethanes (THMs) were used as model analytes. Three types of carbon nanosorbents (graphite, graphene, and multi-walled carbon nanotubes) were studied. The carbon sorbent incorporating membrane was used in a two-phase mode liquid-phase microextraction, with 1-octanol as the acceptor solution. Using a graphite-reinforced hollow-fiber membrane and an extraction time of 10 min, enrichment factors of 40-71 were obtained for trichloromethane, bromodichloromethane, bromoform, and chlorodibromomethane. Linear working ranges of 0.2-100 μg L^-1 and limits of detection ranging from 0.01 μg L^-1 (for CHCl₂Br and CHClBr₂) to 0.1 μg L^-1 (for CHCl₃) were achieved. The minimum detectable concentrations were far below the maximum concentration levels (60-200 μg L^-1) set by the WHO for drinking water. The carbon-sorbent-reinforced hollow-fiber liquid-phase microextraction afforded higher extraction efficiency and shorter extraction time compared with conventional hollow-fiber liquid-phase microextraction. Finally, the method was applied to the analysis of real water samples, such as drinking water, tap water, and swimming pool water samples.