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Fig. 2 | BioData Mining

Fig. 2

From: Label-free data standardization for clinical metabolomics

Fig. 2

Typical mass spectra of human blood plasma metabolites standardized according to the SantaOmics algorithm. a The initial mass spectrum of human plasma metabolites. The mass spectrum was obtained after the direct infusion of a blood plasma sample into an electrospray ion source of a hybrid quadrupole time-of-flight mass spectrometer (maXis, Bruker Daltonics). b Detection of the normalization value for a particular mass (m/z 225) in the mass spectrum. The substances from the selected range (m/z 225 ± 50) of the mass spectrum are plotted according to their decreasing peak intensity. The place of maximum curvature of the curve (knee point), which approximates the range of intensities, corresponds to the normalization value (depicted by the arrow). c Maximum curvature detection by intensity derivative calculations. The derivative maximum (depicted by the arrow) corresponds to the knee point, which indicates the normalization value on the y-axis of plot B. d Normalization curve that was built by approximation of the normalization values calculated over the entire range of the mass spectrum. e Standardized mass spectrum that was obtained by dividing the peak intensities of the initial mass spectrum by the normalization curve

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