Fatty acid methyl ester detection

Each of the subsystems can, apart from the others, make a significant diagnostic contribution. For example, the instrumental cell isolation and sample handling component could be used with DNA-based or other non-MS systems for detection and/or identification. As another example, the principles underlying pattern drift compensation can apply to MALDI MS and even non-MS detection systems such as capillary GC of fatty acid methyl esters. 

TLC spots with marker reveal the presence of free fatty acids (FFA), diglyceride (DG), monoglyceride (MG) but negligible amount of TG. GCMS of fatty acid— methyl esters (FAME) from lion mane presented evidence for fatty acids ranging from C9-C24 (Figs. 5.3- 5.6). Low volatility molecules like nonanedioic acid (Fig. 5.3), tridecanoic acid (Fig. 5.4), 12-methyl tridecanoic acid were also present in lion hair lipids. In addition fatty acids such as myristic, pentadecanoic, palmitic, heptanoic, stearic and octadecenoic acids (Fig. 5.5) have also been detected. Erucic... 

Fig. 18 RP-HPLC of methylesters derived from three different fish oil sources sardine (A), menhaden (B), and cod liver (C). Identified fatty acid methyl esters in order of their elution 1. C20 5o 3 2. C14 0 3. C16 lw9 4. C22 6o>3 5. C18 2a>6 6. C16 0 7. C18 1 >9. BHT is eluted right after the void volume remaining peaks have not been positively identified. Mobile phase acetonitrile/THF/water (9 5 11) at 2.0 ml/min stationary phase WHATMAN ODS-3 RAC II (100 X 4.6-mm ID) detection, refractive index at ambient temperature.

Robinson, J.L., Tsimidou, M. and Macrae, R. (1985) Evaluation of the mass detector for quantitative detection of triglycerides and fatty acid methyl esters. J. Chromatogr., 324, 35-51. 

The most widely used method for quantifying FFAs is gas chromatography (GC), which has attained widespread favor due to its versatility, high sensitivity and relatively low cost. GC complexed with a flame ionization detector is used routinely to quantify FFAs, either directly or derivatized as fatty acid methyl esters (FAME). GC with mass spectroscopic detection has become the favored technique for quantification of volatile compounds derived from lipids (esters, lactones, ketones, alcohols and acids). 

The identification of individual classes of fatty acids has relied on the use of gas chromatography (GC), equipped with a flame ionization detector. Lipids are sapoiufled after extraction and the fatty acids converted to methyl esters. The fatty acid methyl esters (FAME) are separated using GC. The use of standards ahowed for the identification of individual species of fatty acids based on retention time. The method is quite sensitive and permits the quantification of fatty acid species. The mode of detection has been enhanced with the use of mass spectrometry (MS), which allows for the detection and quantification of unknowns, thus increasing the utility of these methods. The Lipid Library section on the gas chromatography of lipids http //www.lipidlibrary.co.uk/GCJipid/01 intro/index. htm) provides a comprehensive description of these methods. 

Analysis of fatty acid methyl esters by using supercritical fluid chromatography with mass evaporative light-scattering detection S. Cooks and R. Smith, Anal. Proc. 28,11 (1991)... 

A) Reference mixture of simple lipid classes, silica gel TLC, mobile phase hexane-ethyl ether-acetic acid, 80 20 2 (v/v/v) SE, sterol esters ME, fatty acid methyl esters TG, triacylglycerols EEA, free fatty acids S, sterols 1,3-DG, 1,3-diacylgly-cerols 1,2-DG, 1,2-diacylglycerols MG, monoacylglycerols C, complex lipids detection by spraying with 5% ethanolic phosphomolibdic acid and heating for several minutes at 180°C. 

The fatty acid methyl esters were analyzed using GC (Model 5890, Hewlett-Packard, Wilmington, DE) equipped with a capillary column (SPB-1,15 m x 0.32 mm, 0.25-pm film thickness, Supelco). Helium was used as the carrier gas at 1 mL/min. The initial column temperature was 160°C, heated at a rate of 5°C/min to 210°C, and then kept at 210°C for 30 min. Detection was done by a flame ionization detector with hydrogen, helium (make-up gas), and air at 27, 29, and 445 mL/min, respectively. The amounts of linoleic acid, THOA, and DEOA were calculated from the peak area relative to that of palmitic acid (internal standard) using stan-... 

Olive oil and other oleic-rich oUs are recognized by their relatively high content of oleic acid, detected as its fatty acid methyl ester (FAME) (peak 3). Palmitic and stearic acid FAMES (peaks 1 and 2) are also detected. Soya bean oil and similarly safflower, sunflower, and dehydrated castor oils contain approximately 60% linoleic... 

The fatty acid methyl esters C16.0, C18.0, and C18.2 indicate the presence of a vegetable oil. However, the detection of isopropyl palmitate (IPP) and isopropyl stearate (IPS) in the Py-GC experiment (not shown) means that there would also be a contribution of their fatty acids to this pyrogram. The methyl ethers of cetyl alcohol (C16-OME) and stearyl alcohol (C18-OME) suggest the presence of the respective free fatty alcohols, and this is confirmed by an inspection of the pyrogram from the Py-GC experiment (not shown). Myristyl alcohol methyl ether (C14-OME) and myris-tic acid methyl ester (CM. 0) originate from myristyl myristate used in the formulation. 

Analysis of the fatty acid profile of the extracted fat is now almost exclusively carried out using gas-liquid chromatography (GLC). Standard methodology for this technique is detailed by the International Union of Pure and Applied Chemistry (lUPAC). It involves the saponification of the extracted fat to break down glycerides, with the liberated fatty acids being esterified in the presence of methanol and boron trifluoride. Fatty acid methyl esters are then extracted with heptane and analyzed using GLC with flame ionization detection. 

In a comparative study of the reproducibility of results obtained by the two techniques for the analysis of blood lipids Mares et al. (1983) concluded that the variations obtained with the TLC-FID system were much higher than those obtained by GC. However, recent improvements in the latroscan detection system are likely to increase significantly the reproducibility for this type of analyses. Sebedio and Ackman (1981) analysed a synthetic mixture of fatty acid methyl esters on silver-nitrate-impregnated Chroma-rods and compared the results with those obtained from conventional GC. Comparable results were obtained by the two methods for all methyl esters, except for methyl linolenate, the quantity of which was substantially overestimated by the TLC-FID method. 

In Chapter 8 a leading expert in the detection of adulteration of oils and fats, Rossell, explains the economic advantages which tempt unscrupulous dealers to add cheap oils to high-value oils such as olive oil. He then describes a technique which he and his coworkers at Bristol have pioneered where stable carbon isotope ratio (SCIR) measurement has simplified the task of detecting adulteration. He compares sterol and fatty acid methyl ester analysis with SCIR and shows how clearly the latter detects maize oil. 

Figure 22-4 Resolution of 22 18-carbon fatty acid methyl esters with 1, 2, or 3 double bonds. Fatty acids shown in Figure 5-3 are labeled (peaks 3, 7, and 14). A Supelco ILIOO ionic liquid wall-coated open tubular gas chromatography column (100 m X 0.25 mm inner diameter with 0.20 xrr film thickness) was operated at 150°C with H2 carrier gas at a linear flow rate of 25 cm/s and flame ionization detection. [From C. Ragonese, P. Q. Tranchida, P. Dugo,...

Fatty Acid Methyl Ester (FAME) Detection The unique fatty acid composition and variability of the relative abundances of these species among microorganisms from different genera have been summarized as early as half a century ago by O Leary (1962). Subsequent developments in increasing sensitivity of mass spectrometers obviated the need for analysis of these nonvolatile, highly abundant compounds for biodefense approaches. Laboratory protocols have been developed to optimize the esterification procedure to increase the yield and minimize the required reaction time. 

FIGURE 20.11 Pyrolyis-mass spectrometry analysis of fatty acid methyl esters (FAMEs) from four pathogenic bacteria mass range 180-350Th range of FAMEs detected C10 0ME-C20 0ME. Source Basile, F.B., Michael, B., Voorhees, K.J. (1998) Pathogenic bacteria their detection and differentiation by rapid Upid profiling with pyrolysis mass spectrometry. TRAC Trends in Analytical Chemistry, 17(2), 95-109. 

Eide, L, Neverdal, G., Westad, F. (2010) Detection of 5 ppm fatty acid methyl ester (FAME) in jet fuel using electrospray ionization mass spectrometry and chemometrics. Energy Fuels, 24,3661-3664. 

Fig. 1.4. Reversed-phase separation of fatty acid methyl esters, including CLA. A Nucleosil C g column (250 x 10 jim i.d. 5 mm particles) was used with acetonitrile as mobile phase, and ultraviolet detection at 234 nm. Methyl esters (20 mg) in acetone were injected, with acetonitrile as mobile phase and a flow rate of 4 mL/min. The fraction corresponding to the C g dienes may also contain some 14 0, 16 1, and certain polyunsaturated fatty acids. (Chromatogram kindly supplied by J.-L. Sebedio and P. Juaneda.)...

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