In biochemistry, a fatty acid is a carboxylic acid typically with a long aliphatic chain, which is either saturated or unsaturated. The majority of naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ranging from 4 to 28. Fatty acids are commonly derived from phospholipids ortriglycerides. Fatty acids are important sources of fuel because, when metabolized, they produce large quantities of ATP. A lot of cell types can use either fatty acids or glucose for this purpose. Long-chain fatty acids cannot cross the blood–brain barrier and so cannot be utilized as fuel by the cells in the central nervous system; nevertheless, free short-chain fatty acids and medium-chain fatty acids can cross the blood–brain barrier, except for glucose and ketone bodies.
The FID method used to be utilized by a large number of lipid analysts to measure Fatty acid methyl ester (FAME) separated by GC. Although FID has proven to be a useful tool for FAME determination, the lack of any selectivity can limit the usefulness of this detector when used to complicated samples, since only instrument response and retention time information may be gathered. Owing to this limitation, misidentification of FAME in the presence of contaminants, artifacts, or coeluting compounds is still of concern when using FID. Thus, much work has been done to maximize the usefulness of retention time for FAME identification through methods such as retention time locking, retention time prediction, and the dependence of retention time on FAME equivalent chain lengths; however, FAME identities assigned by such methods are generally considered tentative. Therefore, FID analysis of complex biological extracts may prove insufficient in some situations, especially for FAME of relatively low abundance.
An investigation of the performance of FID vs. MS in quantifying FAME separated by GC has not been carried out since the work of Koza et al. in 1989. These scientists compared FID response factors of FAME with those obtained using EI in quadrupole as well as sector-type MS. However, only seven FAME were examined, none of which was polyunsaturated. In addition, since this type of MS was still a relatively recent development at that time, the study provided no information to users of ion trap (IT) MS systems. Limits of detection, calibration behavior, and reproducibility of the instrumental methods were not addressed.
Currently, a reliable and reproducible method using highly sensitive LC-MS/MS platform for the identification and quantification of total fatty acids in different sample types has been established by the scientists at Creative Proteomics, which can satisfy the needs of academic and industrial study in your lab.
Total lipid fatty acid profile by GC of methyl esters
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