Fig. 4.

Determination of the limit of detection or quantitation of MALDI-MS analysis of sulfatides using 9-AA as matrix. A mixture of N12:0, N16:0, and bovine brain sulfatides at a molar ratio of 1:1:2 was prepared and MALDI-MS analyses of this mixture after dilution were performed as described in “Materials and Methods.” A: A negative-ion mass spectrum of the mixture at a concentration of 200 fmol/μl. B: A negative-ion mass spectrum of the mixture at a concentration of 4 fmol/μl. C: The linear relationship of the ratios of ion peak intensities of representative bovine brain sulfatide species and each of the selected internal standards with different concentrations of the mixture. The data points represent the mean ± SD from four mixture preparations at each concentration. Note that some error bars are within the symbols. IS, Internal standard.