Abstract
The parameters affecting the separation and quantification of trimethylsilyl ethers of mono- and diglycerides have been investigated by gas-liquid chromatography with QF-1 and SE-30 as stationary phases and a flame ionization detector. Results have been compared with those obtained earlier for triglycerides. The isothermal characteristics of a range of trimethylsilyl ethers of mono- and diglycerides on both stationary phases showed that log retention volume was directly proportional to carbon number and inversely proportional to absolute temperature. However, glyceride derivatives with lower carbon numbers deviated from these relationships. By using various rates of programmed temperature rise, we have determined the elution temperatures (Kelvin scale) of the mono- and diglyceride trimethylsilyl ethers relative to that of glycerol trilaurate. The "carbon equivalent of a trimethylsilyl group" is defined and shown to be useful in comparing the chromatographic properties of different glyceride classes. Weight and molar correction factors have been obtained and used to analyze diglycerides derived from egg and bovine brain lecithins.
Highlights
The isothermal characteristics of a range of trimethylsilyl ethers of mono- and diglycerides on both stationary phases showed that log retention volume was directly proportional to carbon number and inversely proportional to absolute temperature
T o prepare TMS ethers, we dissolved mono- and diglycerides in chloroform (20 mg/ml) and allowed 20 pl portions to react with 5 pl of bis(trimethylsily1)acetamide for 5 min at room temperature. 2.5 p1 of the resultant solution was injected onto the gas-liquid chromatography (GLC) columns
T o judge by both GLC and thin-layer chromatography, monoglyceride silylation by bis(trimethylsily1)acetamide was complete in 1 min, but up to 5 min was required for diglyceride silylation
Summary
The isothermal characteristics of a range of trimethylsilyl ethers of mono- and diglycerides on both stationary phases showed that log retention volume was directly proportional to carbon number and inversely proportional to absolute temperature. Temperature-programmed GLC was used [5] to separate TMS derivatives of mono- (C12-C18)and diglycerides (Cl2-CZ4),though the technique was not claimed to be quantitative.
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