Quantitative whole spectrum analysis with MALDI-TOF MS, Part I: Measurement optimisation

The work summarised in this paper presents the first part of a two-paper series on quantitative whole spectrum analysis with MALDI-TOF MS on skimmed milk. To create a reliable foundation for multivariate, quantitative analysis, optimising measurements (Part I) with respect to well chosen criteria is of high importance. This paper describes the whole process from sample acquisition to final mass spectra using skimmed milk from cow, goat and ewe. Experimental design is employed to search for optimal preparation of the milk samples and optimal MALDI-TOF instrumental settings according to well defined quality measures. The results suggest that optimal parameter settings in a quantitative context may differ from the standard settings used to obtain high resolution spectra in traditional mass spectrometry. Improvements from the worst plausible case to optimised factor levels indicate a 6.96 times higher signal-to-noise ratio and 0.63 times lower inter spectra variation (non-repeatability). These results will be the basis for the main experiment with application to quantitative determination of adulterated skimmed milk (Part II).