Matrix-assisted laser desorption/ionization Fourier transform mass spectrometric analysis of oxygenated triglycerides and phosphatidylcholines in eggtempera paint dosimeters used for environmental monitoring of museum display conditions

Oxidative changes in triacylglycerols and diacylphosphatidylcholines in egg tempera paint strips are used for chemical dosimetry of the quality of the museum environment. High-resolution matrix-assisted laser desorption/ioniz ation Fourier transform mass spectrometry (MALDI-FTMS) was used as a rapid method for the determination of the exact elemental composition of the alte ration products from diacylphosphatidylcholines and triacylglycerols, Light exposure of the egg tempera paints yields oxygenated diacylphosphatidylcho lines and triacylglycerols. In the latter multiple incorporation of oxygen was observed as a recurring mass difference of 15.995, the exact atomic mas s of oxygen. Owing to the high resolution of the FTMS data (routinely 20 00 0 at mit 1000 in broadband mode), oxidation products with different element al compositions but identical nominal mass could be distinguished. Products of oxidative cleavage of triacylglycerols were observed in samples exposed for longer times. The relative intensities of the peaks of singly and mult iply oxygenated triacylglycerols were used to derive the degree of oxygenat ion of the egg lipids in the tempera paint dosimeters. The degree of oxygen ation was found to be directly related to the light exposure time. Exposure to elevated temperature (60 degreesC) for a period of 21 days did not lead to oxygenation of the triacylglycerols and diacylphosphatidylcholines. Exp osure to NOx and SO2 in the dark greatly increased the degree of oxygenatio n. Addition of lead- or copper-containing pigments to the egg binding mediu m (and subsequent storage for 6 months in the dark) led to accelerated conv ersion of egg lipids to oxidised products. Copyright (C) 2001 John Wiley & Sons, Ltd.