Separation column packing

The C8 (octyl reverse phase) is the general "work horse" of reverse phases and is recommended as the first to be tried when attempting to exploit dispersive interaction to achieve a separation. Columns packed with C8 material are available in range of lengths from 3 to 50 cm long and can be packed with particles 3, 5, 10 and 18 m in diameter. Consequently, a wide range of column efficiencies is available to the analyst, which, in the methods development laboratory, should always be readily accessible. 

Marko Varga et al. [45] found that a cleanup column prior to the separation column, packed with a chemically bonded amine material (Nucleosil 5 HN2) was found to be effective in removing interfering humic substances. No influence was found from humic substances in concentrations up to 45 pg L 1 on ion chromatographic analysis of nitrate and sulphate (10-100mg L ) after passage through the cleanup column. 

The main advantages in the use of small-diameter, reduced-length separation columns, packed with small-diameter stationary phase particles are a reduction in solvent consumption, together with an increase in the ability to interface with other techniques. 

The dynamic ion-exchange separations are performed successfully on a wide range of stationary phases, which include PS-DVB copolymers (e.g., Hamilton PRP columns), and chemically bonded silica materials (Cjg, Cg, and phenyl groups). Cjg supports are the most popular choice (e.g., hypersil, merck, and phase separation). Columns packed with 3 or 5 xm particles are used for analytical scale separation of lanthanides. 

Further advances in HPLC instrumentation and column technology were made in 2004, with significant increases to the resolution, speed, and sensitivity in liquid chromatographic separations. Columns packed with smaller particles (1.7 mm) and instrumentation with specialized capabilities designed to deliver mobile phase at 15,000 psi (1000 bars) were needed to achieve a new level of performance. UPLC... 

The particle size of the resin and the void volume of the suppressor column affect the quality of the separation, because both parameters determine the peak broadening. The total volume of the suppressor column should be as small as possible to prevent mixing of the already separated signals. For the resulting suppression capacity, however, the total volume of the suppressor column should be as large as possible. These two requirements are incompatible, so the dimensioning of packed-bed suppressors is always a compromise between the suppression capacity and the peak broadening caused by the void volume. Therefore, it is advisable to use suppressor columns only in combination with separator columns packed with resins that have a particle diameter of more than 15 pm. Under these conditions, the contribution to the total peak variance is small. 

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