Ether lipids mass spectrometry

The conventional approach to solvent extraction is the batch method. Early work with this method was hampered by the low concentration of the compounds present and the relative insensitivity of the methods of characterization. Thus lipids and hydrocarbons have been separated from seawater by extraction with petroleum ether and ethyl acetate. The fractionation techniques include column and thin-layer chromatography with final characterisation by thin-layer chromatography, infrared, and ultra-violet spectroscopy and gas chromatography. Of these techniques, only gas chromatography is really useful at levels of organic matter present in seawater. With techniques available today such as glass capillary gas chromatography and mass spectrometry, much more information could be extracted from such samples [20]. 

Ylinen et al. [53] developed an ion-pair extraction procedure employing tetrabutylamonium (TBA) counter ions for determination of PFOA in plasma and urine in combination with gas chromatography (GC) and flame ionisation detection (FID). Later on, Hansen et al. [35] improved the sensitivity of the ion-pair extraction approach using methyl tertiary butyl ether (MTBE) and by the inclusion of a filtration step to remove solids from the extract making it amenable to liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination. Ion-pair extraction procedure has been the basis of several procedures for biota [49,54-58] and food samples [50,59,60]. However, this method has shown to have some limitations, such as (1) co-extraction of lipids and other matrix constituents and the absence of a clean-up step to overcome the effects of matrix compounds and (2) the wide variety of recoveries observed, typically ranging. 

The title compound, 1,3-dideuteriated malondialdehyde, MDA-46, formed in a lipid peroxidation process involved in the pathogenesis of many human diseases45,46, has been needed for quantitative determination of MDA in human blood or urine by isotope dilution mass spectrometry. It has been synthesized47 by condensation of deuteriated butyl vinyl ether with deuteriated triethyl orthoformate in the presence of montmorillonite clay K-10 (equation 18). 

Egge, H. (1983) Mass spectrometry of ether lipids, in Ether Lipids, Biochemical and Biophysical Aspects, H. K. Mangold and F. Paltauf, editors, Academic Press, New York, pp. 17-47. 

Egge, H. 1983. Mass spectrometry of ether lipids. In Ether lipids Biochemical and Biomedical Aspects. 

To determine sterols, a portion of the total lipid extract is saponified using methanolic potassium hydroxide, and sterols subsequently recovered in 2 1 hex-ane/chloroform. The sterols are converted to the corresponding trimethylsilyl (TMS) ethers using bis-N,0-(trimethylsilyl)trifluoroacetamide, BSTFA, and analyzed by capillary GC and GC with mass spectrometry. Reviews of relative retention times and mass spectra for sterol TMS ethers have been published [e.g. 73]. In some cases, sterol acetates, rather than TMS ethers, are the derivatives prepared for GC. SiHca column chromatography of the total lipid extract may also be used instead of saponification to isolate the sterol fraction [74], or even sterol subclasses such as 4,4-dimethyl, 4-monomethyl and 4-desmethyl sterols [75], prior to derivatization. However, this approach only includes free sterols in the analysis, whereas by saponifying the total extract, sterols present as steryl esters are also detected. 

Christiansen, K Mahadevan, V. Viswanathan C.V. Holman, R.T. (1969). Mass spectrometry of long-chain aliphatic aldehydes, dimethyl acetals and alk-l-enyl ethers. Lipids, Vol.4, No.6, (November 1969), pp. 421-427, ISSN 1558-9307 Christie, W.W. (1988). Equivalent chain-lengths of methyl ester derivatives of fatty acids on gas chromatography A reappraisal. Journal of Chromatography A, Vol.447, pp. 305-314, ISSN 0021-%73... 

Thiel, V.,Toporski, J., Schumann, G, Sjdvall, R, Lausmaa, J. (2007) Analysis of archaeal core ether lipids using time of flight-secondary ion mass spectrometry (ToF-SIMS) exploring a new prospect for the study of biomarkers in geobiology. Geobiology, 5,75-83. 

To reflect these different levels of structural information, a system of shorthand notation for lipid structures derived from MS analysis was proposed [39] and becomes widely accepted. For example, for analysis of PC species, it was proposed to notate with PC(nominal mass) or PC(m n) to represent a detected species by the tandem MS approach (where m and n are the total number of carbon atoms and double bonds of aliphatic chains in the species, respectively) with PC(mi i i2 2) or PC(o-mi ni m2 2) to reflect the identification of individual fatty acyl chains and the ether bond by the high mass resolution mass spectrometry-based shotgun lipidomics and with VCim1.n1lm2.n2) or VCio-m1.n1lm2.n2) to denote the total identification of PC species by MDMS-SL. Similarly, MRM-based methods after... 

Aldehydes are more easily identified than are the parent compounds, since a wide range of standards is available from commercial sources or can be prepared synthetically from other lipids. As an example of the full application of this methodology, more than 30 different bases were detected in the sphingolipids of bovine kidney [469]. Mass spectrometry can be utilised as an aid to identification of aldehydes (see also Section B above), although some workers have preferred to reduce them to fatty alcohols and then to prepare acetate or TMS ether derivatives for this purpose [624]. In addition, all the methods for the location of double bonds in fatty acids, such as ozonolysis or hydroxylation with osmium tetroxide and preparation of TMS ethers for MS, have been utilised with aldehydes prepared from sphingoid bases [464,465]. 

---