Enhanced Sensitivity and Effective Cleanup Strategy for Analysis of Neonicotinoids in Complex Dietary Samples and the Application in the Total Diet Study

Abstract

Extensive residues of neonicotinoids (neonics) have been demonstrated in food and the environment by routine monitoring measurement, but little is known about the residue levels in “ready to eat” dietary samples. To obtain a more accurate picture of dietary exposure to total neonics, an ultrasensitive and effective cleanup analytical method for the quantification of neonics in dietary samples was established on the basis of cold-induced phase separation and pre-column dilution injection liquid chromatography–high-resolution mass spectrometry. A total of 10 neonics were quantified in ultratrace amounts (ng/kg) using stable isotope dilution, with calibration curves spanning 4 orders of magnitude. Satisfactory accuracy (73.5–109.2% for the recoveries) and precision (0.6–13.2% for the relative standard deviation ranges) were obtained in method validation. Moreover, tolerable absolute matrix effects (0.89–1.09) were also obtained in 12 kinds of dietary matrices with weak relative matrix effects (2.8–12.6%). The validated method was applied to the dietary samples collected from the Chinese Total Diet Study, and the results showed that 75% of the samples were contaminated with at least one neonicotinoid.

Nationwide Biomonitoring of Neonicotinoid Insecticides in Breast Milk and Health Risk Assessment to Nursing Infants in the Chinese Population

“…For sample preparation, a slightly modified version of a previous analytical method was used . Briefly, an aliquot of pooled milk (8.0 mL) fortified with 1 ng of each IS was measured into a 15 mL centrifuge tube.…”

“…The target analytes were chromatographically separated on an Accucore aQ C18 column (150 × 2.1 mm, 2.6 μm) at 40 °C using a column oven. All other details of instrumental conditions were carried out as described by the previous method …”

“…For sample preparation, a slightly modified version of a previous analytical method was used. 23 Briefly, an aliquot of pooled milk (8.0 mL) fortified with 1 ng of each IS was measured into a 15 mL centrifuge tube. A total of 4.4 mL of acetonitrile was added to the sample and vortex-mixed to keep the proportion of acetonitrile/water at 37.5% (v/v).…”

“…All other details of instrumental conditions were carried out as described by the previous method. 23 Quality Assurance and Quality Control. To evaluate the background contamination and accuracy and reliability of detection results, a procedural blank and three quality control (QC) samples (spiked blank samples at 50, 100, and 500 ng L −1 ) were included for each batch of 15 samples analyzed.…”

“…As expected, all procedural blanks were lower than the limits of detection (LODs) of all analytes. Method LODs of neonics in breast milk samples were calculated according to the suggestion of the Eurachem guide shown in our previous study 23 and are listed in Table 1. In QC samples, the average recoveries of nine neonics were between 84.7 and 108.4% and the relative standard deviation ranged from 3.6 to 8.6%.…”