DORIS SMITH, KEN LYNAM

Agilent Technologies, Inc. 2850 Centerville Road Wilmington, DE 19809-1610, USA

Abstract

The detection of residual organophosphorous pesticides in processed olive oil is complicated by the chromatographically active nature of these compounds, which compromises chromatographic resolution. This study demonstrates a quick and effective analytical method for the determination of low ppm and trace level OP pesticide residues in an olive oil extract. A J&W DB-35ms Ultra Inert (UI) 30 m × 0.25 mm, 0.25 μm column resolved the pesticides of interest in less than 16 minutes, yielding excellent peak shape for even the more problematic OP pesticides. The detection limits for most of the pesticides were 10–15 ng/mL. A simplified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method provided sufficient sample matrix clean-up while preserving low-level analyte detection. A capillary flow technology (CFT) device was installed post column to split the effluent between the MSD and FPD and implement an automated back flush to diminish residual sample carryover and reduce instrument cycle times.

INTRODUCTION
The health benefits of a Mediterranean diet, and of olive oil in particular, are widely acknowledged (1, 2). However, as 4 kg of olives are needed to produce 1 kg of olive oil, residual pesticides can be concentrated in the final product, and must be monitored to ensure toxic residues do not exceed safe levels (3). Many common insecticides used in olive tree pest protection belong to the organophosphorous (OP) class, and human toxicities for OP pesticides have shown acute as well as chronic effects from pesticide poisoning (4). OP pesticides present a challenge for analysis as they are chromatographically active compounds that can adsorb onto active sites in the sample flow path, particularly at trace levels, compromising the analytes’ response.
Here, we report a sample preparation extraction to detect 16 different pesticides in olive oil samples, using a procedure based on the evaluation of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) approach for the analysis of pesticide residues in the high lipid olive oil matrix (5). This approach simplifies the traditional, labour-intensive extraction and clean-up procedure, ...