Modified Pencil Lead as a New Fiber for Solid-Phase Microextraction

The efficiency of modified pencil lead as a new fiber for solid-phase microextraction (SPME) has been investigated. Modified pencil lead fibers have been prepared by use of several activation processes, for example heating at 600 °C in the stream of inert gas (He), heating under reflux with concentrated H₂SO₄ , fusing with NaOH at 400 °C, and activation at 600 °C with water vapor for 60 min. The fibers were used for extraction of trace amounts of polycyclic aromatic hydrocarbons (PAH) from aqueous samples. Monitoring of extracted compounds and quantitative analysis of model samples were performed by capillary GC–FID. The results obtained prove the suitability of the proposed fibers for sampling organic compounds from water. Effects on extraction efficiency of factors such as temperature, salting out, stirring speed, and exposure time were studied. Under optimum conditions and using one fiber for extraction of naphthalene as a typical compound, a relative standard deviation of 5.3% (n=7) was achieved. The calibration plot was linear in the range 50–10,000 pg mL^–1 (r=0.9997) and the detection limit was 25 pg mL^–1 (S/N=3). This fiber is very stable at high temperature, inexpensive, and can be prepared simply.