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Enhancing detection coverage in untargeted metabolomics analysis by solid‐phase extraction on‐line coupled to LC–MS/MS

Calderón‐Santiago, Mónica, Priego‐Capote, Feliciano, Castro, María D. Luque
Electrophoresis 2015 v.36 no.18 pp. 2179-2187
adsorbents, blood serum, chloroform, electrophoresis, fractionation, gas chromatography-mass spectrometry, humans, metabolites, metabolomics, methanol, nuclear magnetic resonance spectroscopy, resins, silica, solid phase extraction
One of the main limitations of untargeted metabolomics analysis is the low detection coverage of analytical techniques such as NMR, LC–MS, or GC–MS. In this research, the detection coverage of an automated approach configured by the on‐line coupling of SPE to LC–MS/MS was evaluated by combination of sorbents based on different retention mechanisms. The approach was applied to the analysis of human serum using three types of sorbents: alkyl bonded silica, polymeric resins, and mixed‐mode ionic resins. The combination of four sorbents (C18, a modified polystyrene–divinylbenzene resin and two mixed‐mode ionic resins) led to the best extraction results and, therefore, the best detection coverage, which is explained by their complementary retention mechanisms. However, some of the sorbents provide a high detection coverage by themselves, as is the case with C18, which can afford to retain almost 83% of all detected entities. Taking into account the complementarity between pairs of these sorbents (C18 and the polystyrene–divinylbenzene resin with the mixed‐mode ionic resins), dual cartridge SPE–LC–MS/MS configurations were designed for serum analysis. These configurations allowed increasing the detection coverage up to 91% of the total number of molecular features detected with all sorbents tested. An additional benefit of the SPE–LC–MS/MS strategy was the improvement of sensitivity as compared to protein precipitation and fractionation with methanol and chloroform. Thus, an average preconcentration factor of 10–75 was obtained in the SPE‐based approach versus the two‐phase protocol for metabolites extraction.