Polymer monolith microextraction online coupled to hydrophilic interaction chromatography/mass spectrometry for analysis of beta(2)-agonist in human urine

An analytical method based on online combination of polymer monolith microextraction (PMME) technique with hydrophilic interaction LC (HILIC)/MS is presented. The extraction was performed with a poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolithic column while the subsequent separation was carried out on a Luna silica column by HILIC. After 1:1 v/v dilution with 20 mM phosphate solution at pH 7.0 and centrifugation, urine sample was directly used for extraction. After optimization, 85% ACN (containing 0.3% formic acid v/v) was used for rapid online elution, which was also the mobile phase in HILIC to avoid band broadening during separation or carry-over that was usually observed in PMME-RP LC system. Online automation of extraction and separation procedures was realized under the control of a program in this study. The developed method was applied to rapid and sensitive monitoring of three beta(2)-agonist traces in human urine. The LODs (S/N = 3) of the method were found to be 0.05 - 0.09 ng/mL of beta(2)-agonists in urine. The recoveries of three beta(2)-agonists spiked in five different urine samples ranged from 79.8 to 119.8%, with RSDs less than 18.0%.