Liquid Chromatography Detectors - The UV Detectors > The Fixed Wavelength UV Detector > Page 43

Column, length, 10m, I.D., 1 mm, mobile phase tetrahydrofuran, flow-rate 30 ml/min., adsorbent Partisil 10. Column efficiency ca.  250,000 theoretical plates. Solutes benzene, ethyl benzene, butyl benzene, hexyl benzene, octyl benzene and decyl benzene. Such columns must be packed in short lengths (about 1 m) and subsequently joined and are thus somewhat tedious to construct.

Figure 26. The Separation of Some Alkyl Benzenes by Exclusion on a High Efficiency Column.

All the solutes are distinctly resolved despite their having molecular weight differences equivalent to only two methylene groups. The peaks from such columns are only a few microliters in width and so a specially reduced volume sensor cell was necessary to cope with the high efficiencies and allow the consequent improved resolution to be realized. The molecular weight of decyl benzene is 218 and, thus, one methylene group would represent a differential of only 6.4% of the molecular weight.