Matrix effect in guava multiresidue analysis by QuEChERS method and gas chromatography coupled to quadrupole mass spectrometry.

"Quick, Easy, Cheap, Effective, Rugged and Safe" (QuEChERS)-GC/MS analytical technique was used to evaluated matrix effect of twenty-two pesticides in guava. Validation parameters (selectivity, linearity, LOD, LOQ, accuracy and precision) were determined for multiresidue analysis. Statistical test (t-student) was applied to the coefficients of the curves obtained for the guava matrix. The matrix effect (ME) for each pesticide was evaluated through the study of slope ratios obtained of solvent and guava matrix curves. Most of the compounds had positive ME. The rates of recovery were satisfactory (73.97-119.38%), with a coefficient of variation (CV) less than 20%. Analysis of commercial guava samples showed the presence of 5 types of pesticides residues at levels ranging from 0.1 to 0.5 mg·kg(-1). The results reveal the presence of unauthorized pesticides for cultivation of guava. This data can assist government agencies to ensure food security.