All stationary phases in GC offer a selectivity, called polarizability, that is influenced by the sample, but OPTIMA® δ columns offer this valuable feature to a greater extent than any other phase. The polymers consist of cross-linked polysiloxane block polymers, and narrow molecular weight distribution, which are exclusively produced for MACHEREY-NAGEL. Especially polar analytes are able to induce a dipole moment in the stationary phase, so that the molecules show stronger interactions with the phase. This enhanced interaction is maintained at higher temperatures, where normally interactions between molecule and phase become reduced due to the Brownian movement.
We call this phenomenon "autoselectivity", because the stationary phase adjusts itself to the polarity of the analytes.
Thus OPTIMA® δ phases cover broad ranges of polarities. Compared with conventional phases, OPTIMA® δ-3 polarity ranges from approximately the nonpolar OPTIMA® 5 to the midpolar OPTIMA® 1701, while for OPTIMA® δ-6 the polarity covers a range from about the midpolar OPTIMA® 17 to the polar OPTIMA® 210. In conventional midpolar phases the polarity is induced by phenyl, but especially by cyano and trifluoromethyl groups.
The two latter often cause bleeding, which results in severe problems with some detectors. In contrast, the OPTIMA® δ phases show very high temperature limits (340/360 °C), as well as the low bleed levels, which makes them ideal for the use with mass selective (MSD) or phosphorus/nitrogen detectors (PND) in the field of environmental trace analysis.
Key features of the OPTIMA® δ are:
- Wide range of applications/selectivity due to autoselectivity
- Outstanding thermal stability similar to non-polar phases
- Medium polar without CN groups
W. Röder, D. Lennartz, GIT 3/99, p. 226
R. Looser, K. Ballschmiter, J. Chromatogr. 836 (1999), 271-284
R. Baycan-Keller, M. Oehme, J. Chromatogr. 837 (1999), 201 – 210