Use of automated direct sample introduction with analyte protectants in the GC–MS analysis of pesticide residues

Abstract

Automated large-volume direct sample introduction, or difficult matrix introduction (DMI), was investigated in the determination of 44 pesticide residues possessing a wide range of physico-chemical properties (volatility, polarity, pK(a)) in fruit-based baby food by means of gas chromatography-mass spectrometry (GC-MS) with a quadrupole mass analyzer. DMI has advantages over traditional injection because large volumes (up to 30 microL) of potentially dirty sample extracts can be injected into the GC-MS, but nonvolatile matrix components that would normally contaminate the inlet are removed after every injection. The extra matrix and glass surfaces involved in DMI, however, make the system more prone to the matrix-induced chromatographic enhancement effect, which adversely affects quantification of several pesticides. To overcome this problem, matrix-matched calibration standards and/or the use of analyte protectants were applied in the DMI approach, and the analysis of extracts was also compared before and after undergoing clean-up by dispersive solid-phase extraction. For best quantification, clean-up was still needed, and the combination of matrix-matching with analyte protectants gave the most reproducible results. Depending on the application, however, the addition of analyte protectants (a mixture of 3-ethoxy-1,2-propanediol, L-gulonic acid 3-lactone, and D-sorbitol) to sample extracts and calibration standards in solvent (non-matrix matched), gave satisfactory quantification for most of the 44 pesticides tested. The lowest calibration levels for 34 of the 44 pesticides were < or = 10 ng/g, which meets the standard required by the European Union Baby Food Directive (2003/13/EC).

Evaluation of the QuEChERS sample preparation approach for the analysis of pesticide residues in olives

“…Since then, Atas/GL Science developed an automated DSI device compatible with their Optic PTV, and marketed it as difficult matrix injection (DMI) [26,27]. Recently, the company has revised their automated approach with a second generation product.…”

“…Analyte protectants were 3-ethoxy-1,2-propanediol, D-sorbitol, L-gulonic acid c-lactone with 95% or better purity obtained from Sigma and Fluka. A composite stock solution of analytical protectants (10 : 1 : 1 mg/mL of 3-ethoxy-1,2-propanediol, D-sorbitol, L-gulonic acid c-lactone) was prepared in 7 : 3 water/MeCN as described by Cajka et al [27]. A quality check standard solution of 16 lg/mL triphenylphosphate (TPP) was prepared in MeCN containing 1.6% FA.…”

Application of gas chromatography–(triple quadrupole) mass spectrometry with atmospheric pressure chemical ionization for the determination of multiclass pesticides in fruits and vegetables

“…The matrix shields active sites in the liner and column, which reduces interaction of the analytes on these sites, and leads to enhanced analyte peaks. This effect is most pronounced for polar analytes (typically those with strong hydrogen bonding potential) [25]. Looking at those compounds for which this enhancement is not expected (e.g.…”

Decrease in the matrix enhancement effect on pesticides analysis with GC-MS using new types of solid-phase extraction column

“…[1][2][3][4][5] In our previous study, 6) the matrix components of different types of agricultural products, which were pretreated using the Multiresidue Method for Agricultural Chemicals by GC-MS (Agricultural Products) in the "Analytical Method for Residual Compositional Substances of Agricultural Chemicals, Feed Additives, and Veterinary Drugs in Food" under the Japanese Positive List System (JPL) of Ministry of Health, Labour and Welfare (hereafter, called the JPL method), were examined and some common matrices, monoacylglycerols, tocopherols, and sterols, were found in the sample solution. We also concluded that the monoacylglycerols were the most significant component among them.…”