Oxidized multiwalled carbon nanotubes coated fibers for headspace solid-phase microextraction of amphetamine-type stimulants in human urine

Carbon nanotubes (CNTs) have attracted a lot of attention as effective sorbents due to their strong sorption properties and several potential applications in many fields. In this work, the acid oxidized multiwalled carbon nanotubes (MWCNTs-COOH) was coated onto a stainless steel wire by a simple physical adhesion approach to develop solid-phase microextraction (SPME) fibers. By combination of the MWCNTs-COOH coated fiber-based headspace SPME and gas chromatography-mass spectrometry (GC-MS), the developed method demonstrates a good enhancement factor (288-651), low limits of detection (LODs, 0.2-1.3 μg/L) for determination of amphetamine-type stimulant drugs (ATSs) in urine samples. The recoveries of the spiked ATSs (5, 50 and 500 μg/L) were in the range of 88-107%, the calibration curve was linear for concentrations of analytes in the range from 0.5 to 1000 μg/L (R = 0.963-0.999). Furthermore, single fiber repeatability and fiber-to-fiber reproducibility were in the range of 2.3%-6.2% (n = 6) and 5.7%-9.8% (n = 3), respectively. The MWCNTs-COOH coated fiber is highly thermally stable and can be used over 150 times. The method was successfully applied to the forensic determination of amphetamine (AMP) and methamphetamine (MAMP) in human urine samples and satisfactory results were achieved.