A nanoporous carbon material coated onto steel wires for solid-phase microextraction of chlorobenzenes prior to their quantitation by gas chromatography.

A nanoporous carbon material was synthesized by heating potassium citrate without using a template or an activating agent. It is shown to represent a viable coating for use in solid-phase microextraction. The material is thermally stable and mainly consists of amorphous sheets of sp2-bonded carbon. It has an extensive pore structure and a surface area as large as 1236 m2·g-1. The nanoporous carbon was deposited on the surface of steel wires, and the resulting fibers were applied to the extraction of trace levels of chlorobenzenes in water samples. Following extraction by absorbing, the chlorobenzenes were quantified by gas chromatograph in combination with electron capture detection. Extraction temperature and time, and desorption temperature were optimized (80 °C, 10 min and 310 °C). Under optimized conditions, the calibration plots are linear in the following concentration ranges: 2.5 to 100 ng·L-1 (pentachlorobenzene), 5 to 200 ng·L-1 (1,2,3,4-tetrachlorobenzene), 10 to 100 ng·L-1 (hexachlorobenzene) and 10 to 500 ng·L-1 (1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene). Other figures of merit include (a) high enrichment factors (8324 to 9920), (b) low limits of detection (0.10-1.03 ng·L-1), and (c) good reproducibility (relative standard deviations including intra-day and inter-day with a single fiber and fiber-to-fiber were below 6.4% at a mixed concentration level of 2.5, 5, and 10 ng·L-1 respectively in ultra-water). This method was successfully applied to the determination of chlorobenzenes in (spiked) lake waters where it gave recoveries between 82.3% and 104.5%. Graphical abstract A nanoporous carbon material was synthesized by heating potassium citrate without using a template or an activating agent and used as a viable coating of solid-phase microextraction for chlorobenzenes.