Ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction coupled with liquid chromatography-quadrupole-linear ion trap-mass spectrometry for simultaneous analysis of pharmaceuticals in wastewaters

Abstract

A simple, rapid, low environmental toxicity and sensitive ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (US-IL-DLLME) procedure was developed for the extraction of nine pharmaceuticals (paracetamol, metoprolol, bisoprolol, betaxolol, ketoprofen, naproxen, ibuprofen, flufenamic acid and tolfenamic acid) in wastewater, and their determination using high-performance liquid chromatography with a hybrid triple quadrupole-linear ion trap-mass spectrometer (LC-QqLIT-MS). The IL 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and acetonitrile (ACN) were used as extraction and disperser solvent, respectively, for the DLLME procedure, instead of using toxic chlorinated solvent. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, type and volume of disperser solvent, cooling in ice-water, sonication time, centrifuging time, sample pH and ionic strength, were optimized. The ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution using a small volume of disperser solvent (0.5mL of acetonitrile), which increased the extraction efficiency and reduced the equilibrium time. A slight increase in the recoveries of pharmaceuticals was observed when an ice-water bath extraction step was included in the analytical procedure. In this way, enrichment factors between 255 and 340 were obtained. Data acquisition in selected reaction monitoring mode (SRM), allowed the simultaneous identification and quantification of the analytes using two transitions (SRM1 and SRM2). Additionally, the information dependent acquisition (IDA) scan was performed to carry out the identification of those analytes whose second transition was absent or was present at low intensity, also providing extra confirmation for the other analytes. The optimized US-IL-DLLME-LC-QqLIT-MS method showed a good precision level, with relative standard deviation values between 1.1% and 11.3%. Limits of detection and quantification were in the range 0.2-60ngL(-1) and 1.0-142ngL(-1), respectively. Good enrichment factors (255-340) and recoveries (88-111%) were obtained for the extraction of the target analytes in wastewater samples. This method has been successfully applied to analyze effluent wastewater samples from a municipal wastewater treatment plant located in Almería (Spain) and the results indicated the presence of flufenamic acid and metoprolol in concentration levels of 0.1 and 1.3μgL(-1), respectively.