Identifying biomarkers of smoking-related diseases in saliva by GC–TOF MS
A group of researchers based in Germany have successfully used the BenchTOF time-of-flight mass spectrometer to identify biomarkers of smoking-related diseases in a challenging untargeted study – something that has previously proven very difficult to achieve by GC–MS.
Max Scherer and co-workers, based at the bioanalytical contract laboratory ABF in Munich, collected saliva samples from 25 smokers and 25 non-smokers, subjected them to a simple purification and derivatisation protocol, and analysed the extract using a GC–BenchTOF system, with the goal of identifying compounds that could be indicative of smoking-related diseases.
The performance of the analytical system was assessed using a saliva pool spiked with a standard containing 37 exogenous and endogenous metabolites covering a broad range of chemical classes. Rigorous tests of reproducibility, linearity, reinjection, repeatability and stability were then conducted in order to validate the system.
The results of this validation were particularly impressive, with the authors finding that “almost all” standard compounds and internal standards were sufficiently separated and detectable (co-eluting species were unambiguously identified based on characteristic fragment ions). Further testament to the performance of BenchTOF was provided by the comment that “although we used a quite simple and straightforward sample preparation ... satisfactory validation results in terms of precision, accuracy, and linearity could be achieved”. Linear responses for all analytes were found to be in the range 2.5 μM to 2 mM – levels that could not be efficiently achieved by a GC–quadrupole system.
Other advantages of BenchTOF technology demonstrated by the authors in this study included:
- The outstanding intraday and interday precisions for all dilution levels (coefficients of variation <12% and <20% respectively), despite the minimal sample preparation and purification applied.
- How the exceptional sensitivity of BenchTOF facilitates use of relatively low sample loadings, which in turn optimise chromatographic resolution and reduce variations in retention time – a consequence of the reduced incidence of analyte column overload.
- How structural information obtained using BenchTOF allows measurement and identification of numerous classes of analytes in different matrices.
- How the platform-neutrality and flexibility of BenchTOF allows files to be easily exported to third-party software for additional processing if required.
In conclusion, the authors found that thirteen metabolites showed significantly altered levels between the two groups, which they say “could be linked to smoking-related perturbations and may be associated with established detrimental effects of smoking.” From the analytical perspective, it is also a powerful illustration of how the combination of sensitivity, stability and specificity makes BenchTOF instruments ideal for ‘omics’ applications.
If you’d like to find out more about this research, visit the journal’s website to download the article, or contact one of our TOF specialists.
Untargeted metabolomic profiling in saliva of smokers and nonsmokers by a validated GC-TOF-MS method
D.C. Mueller, M. Piller, R. Niessner, M. Scherer and G. Scherer
Journal of Proteome Research, 2013, published online