RATIONALE: During the development and validation of mass spectrometry based method in residue control analysis, it is recommended to evaluate the level of the matrix effect. Often its level is relatively high, despite extensive sample purification. METHODS: The matrix effect in the method for the determination of non-steroidal anti-inflammatory drugs in animal muscle was tested using a post-extraction addition technique. The experiment was performed to assess the impact of chromatographic conditions and design of ion source on the results. Additionally, the impact of phospholipids was tested. RESULTS: The matrix effect signal varied from 36% (64% ion suppression) to 192% (92% ion enhancement), depending on the analyte and species. The internal standard corrected matrix effect was generally lower but was still high for some analytes. Both chromatographic conditions and ion source design have influence on the level of matrix effect; however, this effect was no longer observed after compensation with internal standards. CONCLUSIONS: Currently, no commonly accepted criteria exist for the interpretation of results of determination of matrix effects; such criteria have been proposed in this paper, based on guidelines for bioanalytical methods and results of the study.
RATIONALE: During the development and validation of mass spectrometry based method in residue control analysis, it is recommended to evaluate the level of the matrix effect. Often its level is relatively high, despite extensive sample purification. METHODS: The matrix effect in the method for the determination of non-steroidal anti-inflammatory drugs in animal muscle was tested using a post-extraction addition technique. The experiment was performed to assess the impact of chromatographic conditions and design of ion source on the results. Additionally, the impact of phospholipids was tested. RESULTS: The matrix effect signal varied from 36% (64% ion suppression) to 192% (92% ion enhancement), depending on the analyte and species. The internal standard corrected matrix effect was generally lower but was still high for some analytes. Both chromatographic conditions and ion source design have influence on the level of matrix effect; however, this effect was no longer observed after compensation with internal standards. CONCLUSIONS: Currently, no commonly accepted criteria exist for the interpretation of results of determination of matrix effects; such criteria have been proposed in this paper, based on guidelines for bioanalytical methods and results of the study.