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Abstract One of the major problems in the GC analysis is the unexpected high recovery of matrix-matched standard calibration when compared with matrix-free standard calibration, also known as the “matrix-induced chromatographic response enhancement effect”. The matrix-induced signal enhancement effect happens when an analyte is retained or decomposed by active sites in the inlet (e.g. liner and initial portion of the column). Pesticides with polar structures, e.g., hydroxy, amino, and phosphate functional groups, have a higher chance of binding and reacting with glass and metal surfaces in a heated gaseous state than nonpolar pesticides, e.g., organic chlorinated pesticides. In the presence of plant-derived matrix components in the extract, the interaction of pesticides with active sites is significantly decreased as these matrix components, that are present in excess, occupy most of the active sites, allowing the pesticide molecules to go through the GC system with strongly reduced surface interactions. Therefore, analyte protectants are added to the mixture prior to injection to mask the active sites in the liner. Considering previous studies, this study aimed to find the optimized conditions for each pesticide (matrix effect wise) by comparing different factors (such as injection solvent, analyte protectants solvent and analyte protectants concentration). The obtained results could be summarized as follows: 1- Each Aps solvent/calibration solvent have their own behavior in the compensation of ME for QuEChERS extracts calibration vs. solvent calibration in the GC-MS/MS analysis. 2- Generally, the highest number of pesticides that had ME ≤20% was when n-hexane:acetone (9:1) was the calibration solvent and acetonitrile the Aps solvent. 3- The highest number of pesticides that had ME ≤5% was when acetonitrile was the calibration solvent and acetone the Aps solvent. 4- The worst case was when acetonitrile used as calibration solvent and Aps solvent at low concentration of Aps which resulted in only 75% of the pesticides to have ME ≤20%. However, even in that case the approach is considered to be successful since only 16% of the pesticides had ME ≤20% for non-protected acetonitrile. |