International Symposium for Thin-Layer Chromatography
Participation type:
Póster
Year:
2014
Location:
Lyon (Francia)
AMD has been used in isocratic mode, with n-heptane as mobile phase over increasing migration distances (20-40 mm, in 10 mm steps) to obtain a rapid separation of base oils in Saturates and Aromatics. In addition, as can be seen in another communication to this meeting, an AMD separation using a THF-DCM-n-heptane 20-step gradient with 2 mm step–1 over 90 mm total migration distance can also be applied to base oils. This allows an improved separation of the apolar families of these samples to be carried out.
Attribution of the nature of separated peaks using both AMD conditions has been done by comparison with migration distances of standards (applied individually and spiked with the base oils), selective UV detection at different wavelengths, and on-silica UV recording of peak's spectra. LOD and LOQ of aromatics in base oil have also been obtained from UV chromatograms.
Detection has also been done using fluorescence densitometry by FDIC. Quantification of Saturates involved post-impregnation of silica gel plates with a solution of either berberine sulfate or berberrubine in MeOH (60 mg L-1).
As fluorescent responses of saturated hydrocarbons in berberine depend on the chain length, calibration procedures using this fluorophore must be done by normalization using a calibrant which is representative of the problem sample. Different calibrants have been tested: 1) a mixture of pure alkanes; 2) fractions of Saturates (obtained from the base oils either by flash chromatography, or using a TLC-MS interface).
Unlike in the case of berberine, fluorescence responses of saturated hydrocarbons on berberrubine plates are roughly constant with the number of carbon atoms in the hydrocarbon chain. Then, base oils may be determined using a pure alkane (e.g., C24, C28 or C32) as a single calibrant. Results are discussed and compared with those obtained from HPLC.
AMD has been used in isocratic mode, with n-heptane as mobile phase over increasing migration distances (20-40 mm, in 10 mm steps) to obtain a rapid separation of base oils in Saturates and Aromatics. In addition, as can be seen in another communication to this meeting, an AMD separation using a THF-DCM-n-heptane 20-step gradient with 2 mm step–1 over 90 mm total migration distance can also be applied to base oils. This allows an improved separation of the apolar families of these samples to be carried out.
Attribution of the nature of separated peaks using both AMD conditions has been done by comparison with migration distances of standards (applied individually and spiked with the base oils), selective UV detection at different wavelengths, and on-silica UV recording of peak's spectra. LOD and LOQ of aromatics in base oil have also been obtained from UV chromatograms.
Detection has also been done using fluorescence densitometry by FDIC. Quantification of Saturates involved post-impregnation of silica gel plates with a solution of either berberine sulfate or berberrubine in MeOH (60 mg L-1).
As fluorescent responses of saturated hydrocarbons in berberine depend on the chain length, calibration procedures using this fluorophore must be done by normalization using a calibrant which is representative of the problem sample. Different calibrants have been tested: 1) a mixture of pure alkanes; 2) fractions of Saturates (obtained from the base oils either by flash chromatography, or using a TLC-MS interface).
Unlike in the case of berberine, fluorescence responses of saturated hydrocarbons on berberrubine plates are roughly constant with the number of carbon atoms in the hydrocarbon chain. Then, base oils may be determined using a pure alkane (e.g., C24, C28 or C32) as a single calibrant. Results are discussed and compared with those obtained from HPLC.