A new solid-phase microextraction fiber for separation and determination of methamphetamines in human urine using sol–gel technique

In this study, for the first time a novel selective multi-walled carbon nanotubes (MWCNTs)/ionic liquid based on imidazolium and solid-phase microextraction (SPME) fiber were synthesized by sol–gel technique for headspace (HS) extraction of ultra-trace levels of methamphetamine (MAMP) and 3,4-methylenedioxymethamphetamine (MDMA) from human urine. MWCNTs were functionalized and used to prepare a SPME fiber and characterized by Fourier transform infrared spectra and scanning electron microscopy. The surface investigation revealed a highly porous structure. The fabricated fiber demonstrated a high thermal and chemical stability and long lifetime. Potential factors affecting the extraction efficiency, including extraction temperature and time, stirring speed, sample pH and salt effect, were studied and optimized. Under optimum conditions, the dynamic linear range was between 0.39–250 and 1.5–250 ng mL−1, the detection limits (S/N = 3) were in the range of 0.097–0.39 ng mL−1 and the limits of quantification (S/N = 10) were found to be 0.39 ng mL−1 for MAMP and 1.5 ng mL−1 for MDMA. The relative standard deviations for one fiber (repeatability) (n = 5) were from 4.87 to 5.36 % and between fibers or batch to batch (reproducibility) (n = 3) were in the range of 6.56–6.98 % for MAMP and MDMA, respectively. The developed method was successfully applied for HS-SPME analysis of MAMP and MDMA from human urine. The relative recovery percentages obtained for the spiked urine samples at 10 ng mL−1 were from 86 to 113 %.