Traditionally, MALDI-TOF mass spectrometry has been used very little for quantitative studies. Analysts have usually assumed that potential differences in ionization efficiency between analyte and internal standards and an inherent heterogeneity of the sample spot would limit MALDI-TOF mass spectrometry as a quantitative technique. In addition, conventional MALDI-TOF spectral acquisition has not allowed rejection of saturated peaks which, when averaged with unsaturated peaks, do not provide peak areas or heights suitable for quantitation. However, with the introduction of sophisticated software and high precision spotting robots, the use of MALDI-TOF mass spectrometry for small organic molecule and peptide quantitation has become a viable analytical procedure. Robotic or manual sample preparation combined with automated MALDI-TOF mass spectrometry, using single-shot averaging, is now a viable method for quantitation of small organic molecules and peptides.
Automatic and intelligent spectra acquisition and evaluation
Acceptable calibration curve linearity from robotic or manual sample preparation
Visual Basic for Applications macro for quantitative analysis
Small Organic Molecule Quantitation
Stock standard solutions were prepared in ethanol. Working analyte (4-acetoamidophenol) standard solutions were prepared by serial dilution of the stock analyte solutions with acetonitrile/water 50:50 (v/v). Working internal standard (theophylline) solutions were prepared directly with matrix solution (2 g/L DHB prepared in 50% acetonitrile/50% 0.1% TFA). Equal volumes of the working and internal standard solutions were mixed. The SymBiot I robot was used to spot 0.5 μL of each solution in triplicate onto the MAL