A Comparison between a Two-Dimensional Liquid Chromatography System and a Traditional QuEChERS-LC Method with Regard to Matrix Removal and Matrix Effects in Pesticide Analysis Using Time-of-Flight Mass Spectrometry.

In this study, a fully automated two-dimensional liquid chromatography (2D-LC) system was used for the investigation of the clean-up effect and was compared with a traditional Quick Easy Cheap Effective Rugged and Safe (QuEChERS) liquid chromatography (LC) method. The focus of those investigations was on negative electrospray ionization (ESI) mode. For that purpose, matrix fingerprinting profiles were created. The results allowed a comparison of both methods regarding the estimation of the number and the polarity of detected compounds. Moreover, the results of the present study were compared with the results generated in positive ESI mode (presented in a previous study). Furthermore, the two methods were compared with regard to matrix effects (ME) of 321 analytes in positive ESI mode and 96 analytes in negative ESI mode. In general, fewer compounds could be detected when 2D-LC and/or the negative ESI mode was used. Especially, very polar compounds with m/z values >1000 could be separated and could not be detected anymore when 2D-LC was applied. Furthermore, the best results were obtained for most analytes when 2D-LC was used, although the extent of ME seemed to be higher with 2D-LC.

Comparing a two-dimensional liquid chromatography with a quick, easy, cheap, effective, rugged, and safe protocol-based liquid chromatography method for matrix removal in pesticide analysis using time-of-flight mass spectrometry.

In this study, a clean-up approach using a two-dimensional liquid chromatography (2D-LC) consisting of a hydrophilic interaction liquid chromatography column and a reversed phase column was investigated. A fully automated 2D-LC system was used and compared with a traditional quick, easy, cheap, effective, rugged, and safe (QuEChERS) liquid chromatography (QuE-LC) method. The comparison was based on the results of a validation of selected analytes. It was investigated whether the detectability of analytes could be improved by the use of the 2D-LC. On the basis of these results, the relative detection rates were determined for every matrix. By means of those detection rates, the matrices were categorized regarding their complexity. Furthermore, the applicability of the 2D-LC was tested by participation in the European Proficiency Test in Fruits and Vegetables Screening Methods. In order to evaluate the separation and the elution profile of matrix components, multivariate data analysis was applied. For this purpose, ten matrices were processed in accordance to a QuEChERS protocol and the protocol for 2D-LC analysis. Moreover, the reagent blanks of the corresponding matrix were processed and analyzed by QuE-LC and 2D-LC. The results allowed evaluating the number of detected compounds for both methods. Additionally, the influence of compounds originating from reagent blanks can be estimated. In general, less compounds could be detected when 2D-LC was used. Especially, these were very polar compounds and compounds with m/z values >1500. These compounds seem to originate primarily from the used reagents especially from the citrate salts. However, the most of these compounds could be separated and were not detectable any more when 2D-LC was used. The results of the comparison based on validation and participation in the European Proficiency Test also show a better detectability for the most analytes with 2D-LC.