Assessment of GC-MS response of selected pesticides in apple matrices related to matrix concentration.

A uniform analyte response is required for GC-MS analysis in order to obtain acceptable quantitative results. The response of pesticides in complex matrices is susceptible to variation due to the interactions of co-extractives, both with pesticides or with GC-MS system. This study was conducted to determine the magnitude of the interactions, called matrix effect, and their behavior with the matrix dilution. The response of pyrimethanil (4,6-dimethyl-N-phenylpyrimidin-2-amine), cyprodinil (4-cyclopropyl-6-methyl-N-phenylpyrimidin-2-amine), trifloxystrobin (methyl-(2Z)-2-methoxyimino-2-[2-[[(E)-1-[3(trifluoromethyl)phenyl]ethylidene amino]oxymethyl]phenyl]acetate) and bifenthrin(2-methyl-3-phenylphenyl)methyl-3-[(Z)-2-chloro-3,3,3-trifluoroprop-1-enyl]-2,2-dimethylcyclopropane-1-carboxylate), used in apple crops protection, was evaluated in different concentrations of peel and flesh extracts of Granny Smith, Golden Delicious and Demi Rouge, selected as representatives of different matrix types. The matrix effect ranged from -0.05 to 146.14%, depending on matrix type and pesticide. The highest response variation was observed in extracts of Granny Smith-an enhancement in flesh and suppression in peel extract. With the dilution, the matrix effect decreased with different magnitudes, but for Granny Smith peel extract an inverted effect was observed. The presence of the matrix effect in GC-MS pesticides analysis was obvious, requiring the application of matrix-matched calibration in quantification procedures for each variety, with calibration standards matched by the matrix concentration.