A green microfluidic method based liquid phase microextraction for the determination of parabens in human urine samples

Development of green approaches have emerged as a challenge that highlight the pressing need for nontoxic solvents, miniaturized method and bio-degradable materials. In this regard, an environmentally-friendly microfluidic system based on natural deep eutectic solvents (DESs) immobilized in agarose membranes was developed to extract parabens from urine samples for the first time. A comprehensive study of the support liquid membrane showed that only 3 µL of camphor and thymol (2:1 molar ratio) was an interesting option as a substitute for conventional (toxic) solvents used to date. Other experimental conditions were optimized and pH 4 (HCl) and 12 (NaOH) were selected as sample and acceptor solution, respectively. Both solutions (sample and acceptor) were fixed at 1 µL min^-1 as flow rate. The proposed green microfluidic device was successfully applied for the determination of parabens in urine samples with relative recoveries between 86 and 100% for all analytes. Detection limits and quantitation limits were between 0.011-0.093 and 0.31-0.38 µg mL^-1, respectively. Relative standard deviation was below 7% for all analytes. Furthermore, the environmentally-friendly solvent (Ca:Ty 2:1) used as SLM offered the same advantages in terms of membrane stability allowing consecutive extractions. Results were compared with experiments previously conducted using conventional (polypropylene) membranes, observing that highly green microextraction systems based on natural and biodegradable materials have proven to be an attractive alternative in microfluidic systems.