Determination of tocopherols and vitamin A in vegetable oils using packed capillary column supercritical fluid chromatography with electrochemical detection
✍ Scribed by Francisco J. Señoráns; Karin E. Markides; Leif Nyholm
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 138 KB
- Volume
- 11
- Category
- Article
- ISSN
- 1040-7685
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✦ Synopsis
A recently developed microelectrochemical detector for packed capil-Ž . lary column supercritical fluid chromatography pcSFC has been applied to determine nanogram amounts of tocopherols and vitamin A in vegetable oil samples. With this procedure, no removal of triglycerides, preconcentration, or isolation of the unsaponifiable fraction of the sample was required. The oils could thus be injected with no sample preparation step and their tocopherol contents were determined in less than 20 min. The column used was an 80-cm = 200-m-i.d. silica capillary with a packing of 5-m C particles, while the mobile phase was 18 supercritical carbon dioxide modified with 8% methanol. The amperometric detector, based on a 25-m-diameter platinum microelectrode, was found to yield a better sensitivity than an on-column ultraviolet absorbance detector for the analysis of tocopherols and vitamin A. The amperometric detector was found to be compatible with pressure-programmed conditions using supercritical carbon dioxide modified with methanol. The detection limit was determined to be 260 pg for oxidative detection of tocopherols and 240 pg for vitamin A. The experimental setup, including the microelectrode, could be employed for more than 300 injections during several weeks of continuous use.