Analysis of unsaturated compounds by Ag⁺ coordination ionspray mass spectrometry: Studies of the formation of the Ag⁺/lipid complex

Abstract

Coordination ionspray mass spectrometry (CIS-MS) is a useful tool in the detection and identification of cholesterol ester and phospholipid hydroperoxides and diacyl peroxides. Extensive studies of a series of cholesterol esters using CIS-MS revealed the following: (1) Cholesterol esters with equal number of double bonds as the internal standard showed a linear relative response in the mass spectrometer while compounds with non-equal numbers of double bonds gave a nonlinear relative response. (2) Complex adducts containing cholesterol ester, silver ion, AgF, AgBF 4 , and 2-propanoxide form when silver is in molar excess of cholesterol esters, reducing the [M ϩ Ag] ϩ signal. (3) In a mixture of cholesterol esters where silver is limiting, Ch22:6 and Ch20:4 bind to silver at the expense of Ch18:2 and have a higher signal in the mass spectrometer. (4) In a mixture of cholesterol esters where silver concentration is twofold greater than total cholesterol ester concentration, Ch22:6 and Ch20:4 form large complex adducts more frequently than Ch18:2 and have a lower signal in the mass spectrometer. (J Am Soc Mass Spectrom 2003, 14, 872-880)

Desorption Electrospray Ionization Mass Spectrometry Reveals Lipid Metabolism of Individual Oocytes and Embryos

“…These compounds are easily recognized by the characteristic isotopic pattern of silver due to the addition of silver nitrate to the DESI spray solution [40,41]. As observed in the representative mass spectra shown in Figure 1, the most abundant silver-adduct ions for oocytes were m/z 963.7/965.7 (TAG 52:3) and m/z 965.7/967.7 (TAG 52:2), whereas m/z 993.7/995.7 (TAG 54:2), m/z 757.5/759.5 (18:1 cholesteryl ester), and m/z 686.2/688.2 (squalene) were more abundant in blastocysts.…”

“…The samples (n=82) were submitted to lipid profile analysis in the positive ion mode, in order to detect cholesteryl esters and TAG data by doping the solvent spray with silver ions [40,41,43]. The use of silver nitrate in the DESI-MS solvent spray promotes the formation of lipid silver adducts, which are highly ionizable.…”

The effects of acyl moiety and temperature on the polymerization of sterols

“…Ag + ‐CIS‐MS has been found to be a useful detection method for labile compounds (e.g., lipid hydroperoxides and oligomers) with peroxide (COOC) or ether (COC) linkages, since in‐source fragmentation is reduced by this method. In addition, the method is applicable for the detection of non‐polar unsaturated lipids and compounds having an ester moiety 23. Previously, Ag + ‐CIS‐MS has been successfully applied in the analysis of steryl ester hydroperoxides 18, 24, 25 and more recently in the characterization of free sterol dimers 9.…”

Identification of Novel Autoxidation Products of the ω-3 Fatty Acid Eicosapentaenoic Acid in Vitro and in Vivo

“…The unique fragmentation patterns induced by silver ion coordination were employed to characterize these novel compounds. However, the poor sensitivity of this technique makes it difficult to be used to study these oxidation products in vivo (46). Furthermore, the stability of these peroxides in vivo is virtually unknown.…”