Polymer substrate with surface solvent reservoir for polymer-spray mass spectrometric analysis of hydrophilic drugs

Nonporous, hydrophobic organosiloxane (OSX) polymers with surface reservoirs were developed as sampling supports in polymer-spray mass spectrometry (polyS-MS) for the detection and quantification of hydrophilic drugs, ethyl glucuronide (logP -1.8) and vancomycin (logP -4.4), and a slightly hydrophobic drug, phenobarbital (logP 1.5). OSX polymers with surface reservoirs were prepared by solvent evaporation-induced patterning in the presence of an ionic liquid during sol-gel polymerization of a methylalkoxysilane. The surface reservoir provides a continuous supply of spray solvent, enhancing both signal stability and signal duration when conducting analysis by polyS-MS. Using OSX polymer substrates with surfaces reservoirs, calibration curves were generated with good linearity (R2>0.99) and reproducibility and low data spread over the concentration ranges used to screen each of the drugs tested as compared to paper substrates: ethyl glucuronide, 5 – 1000 ng/mL (methanol) and 50 – 10,000 ng/mL (synthetic urine); vancomycin, 2 – 100 μL/mL (plasma); phenobarbital, 50 – 50,000 ng/mL (methanol) and 50 – 5000 ng/mL (synthetic urine). Quantitative analysis by polyS-MS of phenobarbital samples in synthetic urine at concentrations of 250 ng/mL and 2,500 ng/mL showed good recoveries of 90.2% (RSD 3.51%) and 95.7% (RSD 2.57%), respectively. Compared to paper substrates, OSX polymers gave calibration curves with better linearity and reproducibility, especially at low concentrations, as well as longer signal durations, improved signal stabilities, and increased signal intensities. Little to no sample pretreatment is necessary and the required sample volume is small (1 μL to 2 μL), making polyS-MS easy to use for high throughput sample processing.