Development of pipette tip-based poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith for the extraction of drugs of abuse from oral fluid samples.

In this work, a monolithic polymer based on poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) was prepared inside 200 μL pipette tips for the extraction of drug of abuse from oral fluid samples. After an appropriate surface tip modification, several polymerization mixtures with different monomer/cross-linker ratios, and percentage of porogen were studied. The most appropriate monolith to easily flow organic solvents and oral fluid samples was prepared with a MAA/EDMA ratio of 8:92 wt/wt and dodecanol containing 10 wt% toluene, as porogenic solvent. Parameters affecting the extraction procedure were evaluated and the monolith was characterized in terms of binding capacity, reusability, and precision, using α-pyrrolidinovalerophenone as model compound. Cocaine, diazepam, methamphetamine and 20 new psychoactive substances were determined in oral fluids, using the synthesized poly(MAA-co-EDMA) monolith in-tip on an eight-channel micropipette extraction and ultra-high performance liquid chromatography tandem mass spectrometry. Appropriate recoveries were obtained, ranging from 64 to 115%, with limit of detection values from 0.03 to 0.6 μg L-1, and a high precision with relative standard deviation values lower than 10% for all the evaluated drugs.