Coacervative microextraction ultrasound-assisted back-extraction technique for determination of organophosphates pesticides in honey samples by gas chromatography–mass spectrometry

Abstract

Coacervative microextraction ultrasound-assisted back-extraction technique (CME-UABE)is proposed for the first time for extracting and preconcentrating organophosphates pesticides (OPPs) from honey samples prior to gas chromatography-mass spectrometry (GC-MS) analysis.The extraction/preconcentration technique is supported on the micellar organized medium based on non-ionic surfactant. To enable coupling the proposed technique with GC, it was required to back extract the analytes into hexane. Several variables including, surfactant type and concentration, equilibration temperature and time, matrix modifiers, pH and buffers nature were studied and optimized over the relative response of the analytes. The best working conditions were as follows: an aliquot of 10 mL 50 g L-1 honey blend solution was conditioned by adding 100 µL 0.1 mol L-1 hydrochloric acid (pH 2) and finally extracted with 100 µL Triton X-114 100 g L-1 at 85 °C for 5 min by using CME technique. Under optimal experimental conditions, the enrichment factor (EF) was 167 and limits of detection (LODs), calculated as three times the signal-to-noise ratio (S/N=3), ranged between 0.03 ng g-1 and 0.47 ng g-1. The method precision was evaluated over five replicates at 1 ng g-1 with RSDs lower than 9.5%.The calibration graphs were linear within the concentration range of 0.3-1000 ng g-1 for Chlorpirifos; and 1-1000 ng g-1 for Fenitrothion, Parathion and Methidathion; respectively. The coefficients of correlation were higher than 0.9992.Validation of the methodology was performed by standard addition method at two concentration levels (2 and 20 ng g-1). The recoveries were higher than 90%, indicating satisfactory robustness of the methodology, which could be successfully applied for determination of OPPs in honey samples of different Argentinean regions. Two of the analyzed samples showed levels of methidathion ranged between 1.2 to 2.3 ng g-1.