AOCS CE 2-66 PDF

Unfortunately, standard methods such as AOCS Official Method Ca 5a 12 are not suitable for small-scale analytical lipid determinations, because they require significant quantities of starting material and conversion reagents, and because they are not capable of discerning the free acids from triglycerides in the sample. The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Sampling and analysis of commercial fats and oils. Additional experiments were performed with this sesame oil that was spiked with 0. Place the column under a carrier gas flow e.

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Sar Place the column under a carrier gas flow e. Clearly, when trying to minimize TAG conversion, a lower reaction temperature should be used. Related articles in Web of Science Google Scholar. Apparatus equipped aovs a temperature programmer is recommended. O p e rating the oven by linear heating increases the speed of fatty acid elution but does not improve or reduce the resolution of the gas chromatograms.

The Scientific World Journal It will be n e c e s s a ry to optimize the operating conditions by acting on this parameter or more simply on the deadspace of the columnaccording to whether one wishes to improve the separations or to make a rapid analysis.

HCl-to-oil ratio, temperature and reaction time. Safety devices are available and should be used. Triglycerides with the following chain length were purchased from Sigma—Aldrich and used as received: This was done to assure that any observed FAME recovery differences were a result of incomplete conversion and not due to incomplete hexane extraction, with glyceryl triheptadecanoate used to monitor the completeness of both the esterification reaction and the ease of extraction of the resulting FAMEs, while the methyltridecanoate was used to monitor only the effectiveness of the hexane extraction step for FAME recovery.

In both the large-scale production of biodiesel and in the analytical preparation of Aods, FFA content is an important technical criterion that is critical to selecting the proper processing method. A ratio of 0. Hydrogen, which is used only with capillary columns, can double the speed of analysis, but it is hazardous. The characteristics of the recorder should be: In the case of sesame oil and its reaction products, the unknown peaks were identified by class [monoacylglyceride MAGdiacylglyceride DAG zocs, and TAG] by a combination of retention time matching to known standards and mass spectrometry spectral library matching.

Receive exclusive offers and updates from Oxford Academic. The concentrations of pure components and their reaction products were taken directly from calibration curves. A unique double-spike methodology was also employed in which oil samples were spiked with a TAG conversion standard glyceryl triheptadecanoate and a FAME extraction recovery standard methyltridecanoate. Email alerts New issue alert. Taken together, these results confirm that the selective aoocs of FFA can be performed with minimal transesterification of TAG, using a 2.

The primary drawback to gravimetric methods is the tendency to include co-extracted species that can artificially inflate the lipid quantity. This sample was then reacted in the same manner as the pure component samples, as outlined previously.

Carrier gas—either helium or hydrogen see Notes, 3. Maintain at this temperature for 1 hr or until the aovs stabilizes. FID was chosen because of its ubiquitous nature in chromatographic quantitative analyses, as well as its rugged and less expensive nature when compared with other detectors such as mass spectrometry MS.

View large Download slide. The reactivity of FFA and TAG materials under acid-catalyzed esterificaton conditions was found to differ significantly. Fatty Acid Methyl Esters — SampleQ These parameters were modified from a previously reported study using an on-column injection method for the separation and analysis of total lipids Syringe—max capacity of 10? In many cases, the more preferred method for chromatographic determination of the lipid content is through transesterification of the extracted material 5—7.

The trend observed for TAG reactivity indicates that lowering the acid catalyst—substrate ratio below 2 is effective for minimizing the degree of conversion to FAME. Recorder—If a recorder curve is to be used to calculate the composition of the mixture analyzed, an electronic recorder of high precision is re q u i re d.

A typical reaction for pure component testing is outlined as follows: L, graduated in 0. BoxPittsburgh, PA Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies.

Most commonly, gravimetric methods, whereby the biomass is extracted using non-selective solvent-based methods and the extracted material is subsequently dried and weighed, are used to determine the total lipid content based on the mass of the material extracted 1—3.

Hydrochloric acid trace metal grade was purchased from Fisher Scientific and used as received. It should be of the split-type or on-column see Notes, 1. Preparation of fatty acid methyl esters for gas-chromatographic analysis of lipids in biological materials.

The hexane extracts were dried over fresh anhydrous calcium chloride, filtered via a 0. To demonstrate method effectiveness on a complex biological oil, a well-characterized sesame oil standard was reacted under the optimized selective esterification conditions 2. This study was designed to establish a set of reaction cd and protocol aimed at the selective conversion and determination of free fatty acid in oil mixtures, while allowing the popular and accurate use acos GC—FID for analysis and quantitation of FAMEs.

Official methods and recommended practices socs the AOCS: Standard methods such as AOCS Official Method Ce 8 are excellent for small-scale analytical determinations for common fats and oils, but these methods are also unable to separate the individual chemical species that form FAMEs.

It should be compatible with the apparatus used. The coating should be 0. The most important parameters governing the conversion are temperature and time. The accuracy of the selective esterification method was established by confirming that the total FFA content of the unspiked oil was lower than the spiked oil by the amount of oleic acid spike.

Lipid solvent systems are not equivalent for analysis of lipid classes in the microeukaryotic green alga, chlorella. Close mobile search navigation Article navigation. Most 10 Related.

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Sar Place the column under a carrier gas flow e. Clearly, when trying to minimize TAG conversion, a lower reaction temperature should be used. Related articles in Web of Science Google Scholar. Apparatus equipped aovs a temperature programmer is recommended. O p e rating the oven by linear heating increases the speed of fatty acid elution but does not improve or reduce the resolution of the gas chromatograms.

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Fatty Acids Composition. Research in Plant Sciences. Email: ntsomboh yahoo. Method development and validation is useful for GC and other analytical procedures.

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