What are fatty acids
Fatty acid is a kind of compound composed of carbon, hydrogen and oxygen, and it is the main component of neutral fat, phospholipid and glycolipid. It refers to a long aliphatic hydrocarbon chain with a carboxyl group at one end, which is an organic substance. The general formula of straight-chain saturated fatty acids is C(n)H(2n-1)COOH. The lower fatty acids are colorless liquids with a pungent odor. , Higher fatty acids are waxy solids with no noticeable odor. Fatty acids are the simplest type of lipids, and they are the building blocks of many more complex lipids. In the case of sufficient oxygen supply, fatty acids can be oxidized and decomposed into CO2 and H2O, releasing a lot of energy, so fatty acids are one of the main energy sources for the body. Includes saturated (without double bonds) fatty acids and unsaturated (with double bonds) fatty acids. Generally, most of them are straight chains, and some branches will also appear.
The principle of pretreatment method
The sample is saponified by sodium hydroxide methanol solution to generate fatty acid salt, which is catalyzed by boron trifluoride to generate fatty acid methyl ester from methanol and fatty acid salt, which is extracted with n-heptane.
Applications
Determination of fatty acid composition in polyoxyl (40) stearate
Chromatographic conditions:
Chromatographic column: WEL-PEG20M (30m×0.32mm, 0.25μm).
Column temperature: the initial temperature was maintained at 170 °C for 2 min, and then increased to 240 °C at 10 °C/min and maintained for 30 min
Inlet: 250℃
Detector: FID260℃
Carrier gas: nitrogen
Injection volume: 1 μL
Split ratio: 40:1
Column flow rate: 1mL/min
Hydrogen to empty ratio: 32:200
Chromatograms and Data
Test solution
| Name | Retention time | Area | Height | Plates(USP) | Resolution(USP) | Tailing factor |
| Methyl palmitate | 8.558 | 433986 | 168566 | 256837 | – | 1.048 |
| – | 10.209 | 91106 | 27436 | 213477 | 21.171 | 1.039 |
| Methyl stearate | 10.536 | 305052 | 92093 | 233040 | 3.720 | 1.025 |
In conclusion
Using this methyl esterification method, the fatty acid methyl esters in the samples can be extracted, and the results of WEL-PEG20M (30m × 0.32 mm, 0.25 μm) can meet the relevant requirements in the Chinese Pharmacopoeia 2020 Edition.
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