Pipette tip micro-solid phase extraction (octyl-functionalized hybrid silica monolith) and ultra-high-performance liquid chromatography-tandem mass spectrometry to determine cannabidiol and tetrahydrocannabinol in plasma samples.

This manuscript describes the development of an innovative method to determine cannabinoids (cannabidiol and tetrahydrocannabinol) in human plasma samples by pipette tip micro-solid phase extraction and liquid chromatography-mass spectrometry/mass spectromtery. An octyl-functionalized hybrid silica monolith, which had been synthesized and characterized, was used as a selective stationary phase. The octyl-functionalized hybrid silica monoliths presented high permeability and adequate mechanical strength. The micro-solid phase extraction variables (sample pH, draw-eject cycles, solvent for phase clean-up, and desorption conditions) were investigated to improve not only the selectivity but also the sorption capacity. The method was linear at concentrations ranging from the lower limit of quantification (10.00 ng/mL) to the upper limit of quantification (150.0 ng/mL). The lack of fit and homoscedasticity tests, as well as the determination coefficients (r2 greater than 0.995), certified that linearity was adequate. The precision assays presented coefficient of variation values lower than 15%, and the accuracy tests provided relative error values ranging from 3.2 to 14%. Neither significant carry-over nor matrix effects were detected. Therefore, the pipette tip micro-solid phase extraction/liquid chromatography-mass spectrometry/mass spectrometry method has demonstrated to be adequate to determine cannabidiol and tetrahydrocannabinol simultaneously in plasma samples for therapeutic drug monitoring of patients undergoing treatment with cannabinoids.

Pipette tip dummy molecularly imprinted solid-phase extraction of Bisphenol A from urine samples and analysis by gas chromatography coupled to mass spectrometry.

Molecularly imprinted polymers (MIPs) were synthesized and used as sorbent for Bisphenol A (BPA) pipette tip solid-phase microextraction from urine samples and BPA analysis by gas chromatography coupled to mass spectrometry (GC-MS). The MIPs were synthesized by the sol-gel methodology. Aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) were used as functional monomer and cross-linking reagent, respectively. BPA and tetrabromobisphenol A (TBBPA) were evaluated as template during MIP synthesis. The BPA-based MIP displayed slightly higher extraction efficiency than the TBBPA-based dummy molecularly imprinted polymer (DMIP), but the TBBPA-based DMIP was selected as sorbent to minimize interference from leaked template. Comparison of the TBBPA-based DMIP, BPA-based MIP, and non-imprinted polymer (NIP) extraction efficiencies attested that the TBBPA-based DMIP was selective. The synthesized polymers were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The TBBPA-based DMIP was reused for over 100 times, which confirmed its robustness. The developed method was linear from 50 to 500ngmL-1. Precision values had coefficient of variation (CV) ranging from 4 to 14%. The accuracy relative standard deviation values (RSD) varied from -13.6 to 12.3%.