2014 Volume 12 Issue 2 Pages 123-133
Liquid chromatography-triple quadrupole mass spectrometer (LC/MS/MS) using electrospray ionization (ESI) is a commonly used analytical method for environmental safety even though there are limitations to its robustness. One of the limitations, the matrix effect (ME), is defined as the ionization suppression/enhancement by the co-eluting residual component, which creates large uncertainties in quantification. The objective of this study is to address ME in the analysis of pesticides and their transformation products in water matrices. For a set of 164 environmental samples, which were preconcentrated by a solid-phase extraction, ME was estimated by spiking standard solution containing 27 target chemicals. As a result, ionization suppression occurred in most of the analytes/matrix pairs. Variability in ME was also observed and the variability among analytes was derived from co-eluting matrix component rather than the physicochemical property of each analyte. To overcome ME, the preconcentrated samples were successively diluted and the effective dilution factor was determined. The variability among diluted samples was still observed and therefore ME needs to be confirmed in every sample for reliable quantification. Sample dilution worsens the limit of quantification; however, the limits in the method were maintained below 0.01 μg/L.
