GC-MS – Multimedia

A new dual-layer cartridge for the efficient extraction of PAHs from edible oils

A GC/MS or LC/MS workflow for Metabolomics applications includes a number of distinct steps: experimental design, sampling, sample preparation, data acquisition, data processing, deconvolution, identification and data interpretation.

The MsXelerator software includes Quality Control procedures and Analysis of Variance (ANOVA) to properly control each step in this workflow and to obtain reliable results for both quantitation and identification.

A sharp, narrow, and sensitive peak is a pre-condition for a sensitive GC analysis. Therefore, a protectant is needed to protect the analyte from any type of distortion for integration and to prevent overestimation. Existing solutions do not overcome these problems completely due to limitations. As the matrix enhancement problem originated from matrix components, its solution should come from similar components.

Acetonitrile was used as the extraction solvent with sodium chloride to enhance the partitioning of analytes into the organic phase. Recovery indicated good method accuracy and repeatability, and was within the acceptable range for residue determinations. The mere presence of pesticide residues in tea does not necessarily mean that the tea has become toxic and would pose a health hazard. We revealed that only a negligible or small percentage of pesticides in tea is transferred to the infusion.

The dSPE of QuEChERS was replaced with an SPE cartridge, which provided a very clean chromatogram, although a small recovery percentage was obtained. The method fulfilled all validation criteria and was useful for monitoring etoxazole residues in red pepper. It can also be used and optimized for other fruit and vegetable matrices.

QuEChERS involves an initial step when a few grams of the sample are extracted with acetonitrile followed by a clean-up step (with dispersive-SPE) used to remove, to a certain extent, unwanted matrix compound (such as pigments, sugars, organic acids). With QuEChERS, the final extract ends up with the pesticides in acetonitrile, which, being polar solvent, can be
problematic in GC-MS.

Analysis of Herbal powders or ‘churnas’ using an optimized GC-MS/MS method is described. As they have high amount of matrix co-extractives, they pose critical analytical problems. The purpose of this work was overcome the effect of the matrix and develop a reliable method.

Analysis of dithiocarbamate pesticides (DTCs) using an optimized GC-MS method is described. DTCs are not stable and cannot be extracted or analyzed directly. The purpose of this work was develop a reliable method for identification and quantification of residues.

The data summarized in this presentation dispels myths associated with the utilization of GC-MS for analytes which are critical for metabolomic studies. GC-HRT provides high quality, accurate mass data for:
-Spectral similarity searches (NIST, Wiley, etc.)
-Formula determination (fragment, molecular & adduct ions)
-GC-HRT is an indispensible tool for the analysis of complex biological samples.

Analyses of the M. truncatula extracts were performed, and data processing focused on qualitative analyses. This provided the opportunity for known analyte verification and unknown identification in a meaningful matrix and the demonstration of the key attributes and benefits of GC-HRT.