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Matrix Effects in Multi-Residue Pesticide

Analysis When Using Liquid Chromatography-

Tandem Mass Spectrometry

By Kai Zhang, Ph.D., U.S. FDA Center for Food Safety and Applied Nutrition

Innovators in Chromatography

A continuing series of guest editorials contributed by collaborators and internationally recognized leaders in chromatography.

Dr. Zhang

is a Chemist in the Methods Development Branch of the U.S. FDA Center for

Food Safety and Applied Nutrition. His research interests focus on trace analysis of various

contaminants, such as pesticides and mycotoxins, in foods using LC-MS and GC-MS.

Consumption of pesticide-contaminated food via daily diet is a major source of

exposure to pesticides and poses a potential health threat to humans. It is nec-

essary to monitor various pesticide residues in foods via multi-residue analysis

procedures, because it would be impractical to develop individual analytical

methods for every pesticide in suspected food commodities. The availability of

liquid chromatography-tandem mass spectrometry (LC-MS/MS) has improved

the selectivity and sensitivity of pesticide analysis, as well as workflow in the

identification and quantification of various classes of pesticides in agricultural

products. This leads to the development and use of LC-MS/MS multi-residue

methods in laboratories worldwide to do consistent, targeted quantitative pes-

ticides analysis from a single injection, providing increased sensitivity and the

ability to screen a large number of target pesticides in one method.

The effect of the matrix is a phenomenon in electrospray ionization (ESI) LC-

MS/MS analysis that impacts the data quality of the pesticide analysis. Matrix

effects, caused by analyte and matrix component interactions, are unique to

ESI-based LC-MS/MS instrumentation and present one of today’s most challeng-

ing analytical issues. Matrix effects can take the form of interference or signal

suppression/enhancement (when compared to a pure analytical standard) and

depend on the sample matrix, target analytes, and mode of ionization. Studies

of matrix effects are essential to the application of LC-MS/MS with different food