Hypersil Silica

Even when the trifluoroaeetyl-(+)-camphor ligand is linked to a solid support (Hypersil silica 205d), if retains its activity both in terms of yield and optical induction. 

FIGURE I A reconstructed extracted ion chromatogram of nicotinic acid and its six metabolites under HILIC conditions. Column Hypersil silica (4.6 X 50 mm) at a flow rate of 4 mL/min. Mobile phase A is water, mobile phase B is acetonitrile, both containing 1% formic acid. Gradient is 0.01-0.25 min 90% B to 65% B 0.25-0.90 min 65% B to 50% B. NA nicotinic acid NAM nicotinamide NUA nicotinuric acid 2-PY l-methyl-2-pyridone-5-carboxamide l-MNAM I-methyl-nicotinamide NAMO nicotinamide-N-oxide 4-PY l-methyl-4-pyridone-5-carboxamide. (Reprinted with permission from Reference 20.)... 

Fig. 3.1. Separation of the unbonded silica test mixture using in-house packed (A) Hypersil silica, (B) Hypersil BDS silica, (C) Hypersil HyPURITY and (D) Kromasil silica capillaries (100 pm i.d., 33.5 cm total length and 25 cm effective). Conditions 8 2 v/v ACN-50 mM MES, pH 6.1, 20 kV, 20°C, 5 kV for 3 sec. injections, 254 nm. Peak identities 1 = biphenyl, 2 = benzamide, 3 = benzyl alcohol and 4 = thiourea. Adaptation of [20]. Reproduced with die permission of Chromatographia.

Benzyloxycarbonyl, N-(3,5-dinitrobenzyloxy carbonyl), 9-fluorenylmethoxycarbonyl, benzoyl, acetyl and N-(2,4-dinitrophenyl) derivatized amino acids and profens WAX (weak anion-exchange) type CSP tert. -butylcarbamoylquinine as chiral selector on Hypersil silica gel), 3 pm Acetonitrile-methanol (80 20)+400 mM acetic acid+4 mM triethylamine 335 mm x 100 pm i.d. 250 mm effective length, chiral separation... 

Muller (13) studied the retention characteristics of the different silicas for different analytes with different functional groups. For benzene derivatives with polar functional groups, a significant influence of the surface pH of the silica was found only for acidic and basic analytes, such as phenol and anilines. Compared to methyl phenyl ketone, phenol was less retained on the acidic Zorbax silica and more retained on the basic Spherisorb and Hypersil silicas. It also exhibited strong tailing on the basic silicas. Conversely, aniline. 

It should be pointed out that separation of more than one class of organic compounds can be achieved by SFC. For example. Fig. 1 shows the chromatogram of 35 PAHs, herbicides, and phenols from a contaminated water sample. Solid-phase extraction was used for sample preparation. Five Hypersil silica columns were coupled in series for separation of these contaminants. The percentage of methanol (as modifier) was varied from 2% (5 min) to 10% (29 min) at 0.5%/min. A pressure program was also applied. A diode-array detector was used in this work. 

Very high separation efficiencies (more than 100000 plates) can be achieved by coupling several packed columns in series (e.g.. Fig. 45 shows a separation of triazine pesticides with ten 2(X)x4.6 mm i.d. hypersil silica (5 pm) columns in series—note that the pressure drop over all these columns is only 12.4 MPa. This would not be possible in HPLC since, because of the higher viscosity of the solvents, the back-pressure over the eolumn would become too high (high-pressure shutdown). 

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