Automation of ionic liquid enhanced membrane bag-assisted-liquid-phase microextraction with liquid chromatography-tandem mass spectrometry for determination of glucocorticoids in water

摘要

A novel fully automated liquid-phase microextraction (LPME) procedure making use of a conical polypropylene membrane bag to hold the solvent, coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with positive electrospray ionisation was developed to determine glucocorticoids (including cortisol, cortisone, dexamethasone, prednisone and prednisolone) in water. The solvent was a synergistic mixture of 10% v/v of ionic liquid, 1-butyl-3-methylimidazolium methylsulfate in n-octanol. The use of ionic liquid as an additive enhanced the extraction performance due to the favourable ionic and hydrogen bonding interactions with the analytes. Different experimental parameters such as the types of organic solvent as supported liquid membrane and ionic liquid, various composition of ionic liquid, volume of extractant phase, agitation time and speed, temperature of extraction were investigated. Under the most favourable extraction conditions, enrichment factors of 49.4-83.1 were obtained for the target compounds with relative standard deviations of 10%. The intra-day repeatability of the method ranged from 4.23 to 6.42% and the inter-day reproducibility ranged from 6.87 to 9.20%. Good linearity 0.05-50 ng mL(-1) (prednisolone) and 0.1 -50 ng mL(-1) (all other analytes) with coefficients of determination of 0.991 or better, was obtained. The membrane bag-assisted-LPME UHPLC-MS/MS approach exhibited high sensitivity, linearity and repeatability for the extraction of the glucocorticoids and also offered an automated streamlined process, from the point where analytes were extracted, to the final analysis of the water samples. The method was employed to determine the concentration of these contaminants in the influent and effluent of a wastewater treatment plant. (C) 2018 Elsevier B.V. All rights reserved.