The
effect of makeup solvent composition in ultrahigh-performance
supercritical fluid chromatography-triple quadrupole mass spectrometry
using electrospray ionization was studied using a set of 91 compounds,
3 stationary phases, and 2 organic modifiers of the mobile phase.
The 24 tested makeup solvents included pure alcohols and methanol
in combination with commonly used additives such as water, formic
and acetic acid, ammonia, and ammonia salts with varying molarity.
The behavioral trends for different makeup solvent additives were
established in the first step. Subsequently, the correlations between
physicochemical properties and the MS responses were calculated using
the Pearson correlation test and matrix plots. The regression analysis
was performed using five descriptors: molecular weight, pK
a, log P, number of hydrogen donors/acceptors,
and the MS responses obtained with methanol as the makeup solvent.
The resulting regression equations had a high prediction rate calculated
as R
2-predicted coefficient, especially
when 10 mmol/L ammonium in methanol was used as an organic modifier
of the mobile phase in positive mode. The trueness of these equations
was tested via the comparison between experimental and predicted responses
expressed as R
2. Values of R
2 > 0.8 were found for 88% of the proposed equations.
Thus, the MS response could be measured using only one makeup solvent
and the responses of other makeup solvents could be easily estimated.
The suitability and applicability of determined regression equations
was confirmed by the analysis of 13 blind probes, i.e., compounds
not included in the original set of analytes. Moreover, the predicted
and experimental responses followed the same increasing/decreasing
trend enabling one to predict makeup solvent compositions leading
to the highest sensitivity.
Gastrointestinal stromal tumours (GISTs) are the major nonepithelial neoplasms of the human gastrointestinal tract with a worldwide incidence between 11 and 15 per million cases annually. In this study the acid and non-acid glycosphingolipids of three GISTs were characterized using a combination of thin-layer chromatography, chemical staining, binding of carbohydrate recognizing ligands, and mass spectrometry. In the non-acid glycosphingolipid fractions of the tumors globotetraosylceramide, neolactotetraosylceramide, and glycosphingolipids with terminal blood group A, B, H, Lex, Lea, Ley and Leb determinants were found. The relative amounts of these non-acid compounds were different in the three tumour samples. The acid glycosphingolipid fractions had sulfatide, and the gangliosides GM3, GD3, GM1, Neu5Acα3neolactotetraosylceramide, GD1a, GT1b and GQ1b. In summary, we have characterized the glycosphingolipids of GISTs and found that the pattern differs in tumours from different individuals. This detailed characterization of glycosphingolipid composition of GISTs could contribute to recognition of new molecular targets for GIST treatment and sub-classification.
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