Dispersive liquid-liquid microextraction based preconcentration of selected pesticides and escitalopram oxalate, haloperidol and olanzapine from wastewater samples prior to determination by GC-MS

Abstract

Abstract A multivariate experimental design was used to attain optimum conditions of a dispersive liquid-liquid microextraction (DLLME) method for preconcentration of pesticides and pharmaceuticals for determination by gas chromatography mass spectrometry (GC-MS). Experimental design enabled parameters to be evaluated for their effects on extraction output as well as their interactive effects. The optimum parameters suggested by the design model were 200 µL of chloroform, 1.96 mL of ethanol and 40 s vortexing period. Limits of detection and quantification (LOD and LOQ) were calculated using linear calibration plots of the analytes developed in the standard concentration range of 2.0 µg/L-2.0 mg/L. Enhancement in detection power of the analytes recorded by the optimized method with respect to direct GC-MS determination (based on LOD values) was in the range of 3.6 and 539 folds. Spiked recovery experiments for municipal, medical and synthetic wastewater samples yielded low recovery results when calculated against aqueous standard solutions. Matrix matched calibration standards were used to mitigate interferences from the waste samples, and the percent recoveries obtained were close to 100%. This established accuracy and applicability of the developed method.