[Technical Report] Characteristics of C30 HPLC Column Wakopak Navi C30-5
This article was written by Mamoru Kubota, FUJIFILM Wako Pure Chemical Corporation, for Vol. 69, No. 3 (July 2001) of Wako Junyaku Jiho. The content of this article is from the time of publication. It is not the latest information due to new knowledge and changes in regulatory rules after original publication.
While, as a reverse-phase HPLC column packing, C18(ODS) modified silica gel with a broad range of applicability and excellent durability is still the focus of interest, silica gel bonding alkyl groups shorter (C1, C4, C8) or longer (C22, C30) than C18 are also used for research analysis and quality test.
Among them, C30 (triacontyl group) modified silica gel has attracted attention in recent years, and many investigations have been conducted on its resolution characteristics and recognition ability for the molecular structure.1-3)
In the case of C30 modified silica gel, it is presumed that it has solute selectivity and shape recognition ability that cannot be obtained with C18 because long, hard and elongated alkyl chains are bonded to the surfaces of the porous silica gel.4) C30 modified silica gel has been found to show excellent separation, especially for homologue separation in reversed phase chromatography. On the other hand, according to reports, when polar compounds were separated using 100% aqueous mobile phase using C30 modified silica gel, high reproducibility was obtained in the retention capacity of the analyte.5)
In order to evaluate the selectivity and shape recognition ability of Wakopak Navi C30-5 column packed with C30 silica gel, comparative analysis of carotenoid standards and vitamin E homologue standards were performed using Wakopak Navi C18-5 (C18 silica gel) and Wakopak Navi C22-5 (C22 silica gel). The results are shown in Figures 1 and 2.
For α- and β-carotenes, the resolutions were improved in the order of C18-5 < C22-5 < C30-5 under the same HPLC conditions. For vitamin E, the numbers of methyl groups that bind to the aromatic ring of β- and γ-tocopherols are the same, and thus both tocopherols were coeluted for the C18 and C22 columns. However, for the C30 column (Wakopak Navi C30-5), γ-tocopherol was eluted earlier, and resolution was achieved. In addition, for the vitamin E analysis using Wakopak Navi C30-5, when comparative study was performed using 100% methanol or 100% acetonitrile as the mobile phase, the resolution of β and γ-tocopherols tended to be higher in 100% acetonitrile.
Based on the above, as characteristics of the type C30 silica gel, the following were confirmed:
- The shape recognition ability is high, and it is excellent in resolution and analysis of homologues.
- Resolution can be expected even when resolution is difficult with C18 and C22 silica gel.
For Wakopak Navi C30-5, the functional group is chemically modified to a polymeric type, and specific behaviors such as reverse of the elution order based on this binding mode be exhibited.
In the future, highly accurate techniques to resolve and analyze homologues will become essential. To what extent the C30 silica gel can contribute to these analyses? Accumulation of applied data is anticipated.
References
- C.Sander, K.E.Sharpless, N.E.Craft, S.A.Wise: Anal.Chem., 66, 1667 (1994).
- Emenhiser, L.C.Sander, S.J.Schwartz: J.Chromatogr.A, 707, 205 (1995).
- Pursch, S.Strohschein, H.Hä ndel, K.Albert: Anal.Chem., 68, 4107 (1996).
- Strohschein, M.Pursch, D.Lubda, K.Albert: Anal.Chem., 70, 13 (1998).
- Enami, N.Nagae: Chromatography, 19 (4), 380 (1998).