Polystyrene isocratic separation

Recent chromatographic data indicate that the interactions between the hydrophobic surface of a molded poly(styrene-co-divinylbenzene) monolith and solutes such as alkylbenzenes do not differ from those observed with beads under similar chromatographic conditions [67]. The average retention increase, which reflects the contribution of one methylene group to the overall retention of a particular solute, has a value of 1.42. This value is close to that published in the literature for typical polystyrene-based beads [115]. However, the efficiency of the monolithic polymer column is only about 13,000 plates/m for the isocratic separation of three alkylbenzenes. This value is much lower than the efficiencies of typical columns packed with small beads. 

Fig. 3. Isocratic separation of oligomers from a polystyrene standard (M = 2100 g/mol) on a silica column (250 x 4 mm do = 6 nm dp = 5 pm). Injection m0 = 0.3 mg in 10 pi eluent n-pentane — tetrahydrofuran (87 13, v/v) flow rate 1 ml/inin UV detection at 254 nm. (From Ref.14) with permission)...

Benzoic acid, SA, and EsHBA can be also well separated using an isocratic elution. After separation on a Sep-Pak C)g cartridge, the sample was injected on a Rhodex RSpak DS-613 column containing a rigid polystyrene-divinylbenzene resin. An eluent, 0.05 M potassium dihydrogen phosphate-acetonitrile (60 40), was directed to the UV detector, which operated at 230 nm (2,55). 

Methods of Separation. Elution Behavior. First, elution was performed by an isocratic elution mode. At a constant column temperature, the copolymers and homopolymers of polymethacrylates and polyacrylates were retained in the column with chloroform (and DCE) without ethanol. Only polystyrene could elute from the column. By adding ethanol to chloroform (and DCE), copolymers with a higher styrene content started to elute, and by increasing the ethanol content in the mobile phase, copolymers with less styrene were eluted. 

The use of normal phase silica columns was also described but after acetylation of the flavonoids and then isocratic elution on silica gel. Polystyrene divinylben-zene as a stationary phase was also found to give satisfactory separation and good peak shapes without using... 

Fig. 5-11. Isocratic purification of the crude synthetic peptide, ACP (65-74), from its truncated failure sequences using the polystyrene reversed phase matrix, PLRP-S 100 A (Polymer Laboratories). Column dimensions, 150mmx4.6mm ID and the eluent was acetonitrile/water (20 80 v/v) containing 0.1% TFA. (A) Shows the separation of approximately 5 pg of peptide, (B) shows the separation of approximately 1 mg of peptide.

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