Matrix Effects in GC–MS Profiling of Common Metabolites after Trimethylsilyl Derivatization

Abstract

Metabolite profiling using gas chromatography coupled to mass spectrometry (GC–MS) is one of the most frequently applied and standardized methods in research projects using metabolomics to analyze complex samples. However, more than 20 years after the introduction of non-targeted approaches using GC–MS, there are still unsolved challenges to accurate quantification in such investigations. One particularly difficult aspect in this respect is the occurrence of sample-dependent matrix effects. In this project, we used model compound mixtures of different compositions to simplify the study of the complex interactions between common constituents of biological samples in more detail and subjected those to a frequently applied derivatization protocol for GC–MS analysis, namely trimethylsilylation. We found matrix effects as signal suppression and enhancement of carbohydrates and organic acids not to exceed a factor of ~2, while amino acids can be more affected. Our results suggest that the main reason for our observations may be an incomplete transfer of carbohydrate and organic acid derivatives during the injection process and compound interaction at the start of the separation process. The observed effects were reduced at higher target compound concentrations and by using a more suitable injection-liner geometry.

Matrix effects demystified: Strategies for resolving challenges in analytical separations of complex samples

“…If there is a significant decrease in S/N in the matrix, it is a positive confirmation of the presence of MEs. Variances in S/N can be indicative of ME through either matrix enhancement or matrix suppression [15].…”

“…Instead, active sites can be reduced through careful selection of inlet liner materials, and optimization of injection, temperature, and column flow rate,which can lower the number of active sites and potentially lessen ME in the inlet [42]. Different liner designs and materials can affect the adsorption, absorption, or desorption of matrix components [15,42]. Polar compounds that contain a carbonyl, organophosphate, or amino groups and are capable of hydrogen bonding tend to experience ME in GC-MS analysis, these compounds are easily adsorbed by a non-deactivated straight liner, which can result in peak broadening and shifts in retention time [40,43].…”

“…The sample is injected into the micro vial placed in a liner and then inserted into the inlet, rapidly heated while analytes are transferred to the column for separation. Once completed, the liner with the micro vial is removed from the system, and avoidance of non-volatile matrix components from entering the inlet is achieved [15,45]. In comparison to other injection techniques, this creates a larger surface area in the inlet which will require further deactivation, and the activity of the inlet can vary greatly as a new linear and micro vial is introduced with each injection [15,42,45].…”

“…Extensive fragmentation from coeluting matrix components can result in interference and significant loss of sensitivity [42, 47]. It is suspected that for EI ion suppression to occur the charged ion must transform into another product either by the reaction with another species or recombination with an ion of opposite charge [15, 40, 42, 46]. A study conducted by Parinya Panuwet et al.…”

“…Illustration on matrix-induced chromatographic enhancement. Reproduced with permission[45].an ion of opposite charge[15,40,42,46]. A study conducted by Parinya Panuwet et al theorized the binding of target ions through opposite electron affinity with other ions present in the matrix[10].…”