Exsil Paragon RP18  =  Exsil Pure RP18M

Exsil reversed phase silicas have an outstanding record for reproducibility and are available in a wide range that offers alternative selectivities to conventional reversed phase media. However due to a continuing demand for a phase which combines conventional selectivity with Exsil performance we have drawn on our experience of over 20 years of phase development to produce

Exsil Paragon  RP18

These features:



  • High Purity Silica:                 Good chromatography of acids, bases and neutrals
  • High efficiency:                      Typically 100 000 plates/m for 5µm
  • Cost effective:                         High performance at lower cost.
  • Reproducibility:                     Typical Exmere reliability
  • Conventional selectivity:      Direct alternative to many RP phases.
  • 120A in 3,5 and 10µm:         Ideal for small to medium sized molecules.
  • Carbon loading:                    Very high alkyl loaded (pH stable up to 11)

This selectivity is combined with good peak shape for acids and bases together with high efficiency  (typically 100,000 p/m) to deliver excellent resolving power for difficult samples both in isocratic,

Sample: Nicotine, Quinine, Diphenhydramine, Nortryptiline, Dichlorophenoxyacetic, proprionic and butyric acids

Eluent:   50% MeCN/50% 60mm potassium phosphate pH 2.8

 at 35oC                

Column: 150 x 4.6 mm Exsil Paragon 5 µm RP18

… and gradient separations


Sample and

Column; As above


Gradient:  5 to

65% MeCN/0.1%

TFA in 30 min at




Gradient applications are facilitated by low levels of bleed which are illustrated by these chromatograms of gradients from 0.1% TFA to MeCN/0.1% TFA for three runs with a column and one without using an ELSD.

The high performance is maintained at neutral pH with strongly basic compounds giving low asymmetry peaks.

The asymmetry is measured at 10% peak height; the USP symmetry would be lower e.g. 1.21 for Amitriptyline.

Sample: Uracil, Propanolol, Diphenhydramine, Acenaphthene and Amitriptyline

Eluent: 80% MeOH/20% 20 mM Potassium phosphate pH 7.0, 35oC

Column: 150 x 4.6 mm Exsil Paragon 5 µm RP18

Stable at pH12

The high phase loading and full end capping helps the phase to maintain reasonable stability at high pH providing the level of organic modifier is above 50% and the temperature moderate. In this case, room temperature.

The 120A pore size means that Exsil Paragon not only excels with small molecules but also has extended molecular weight capability to tackle peptides such as the decapeptide Bacitracin…

Sample:     Bacitracin           

Column:    150 x 4.6 mm Exsil Paragon 5 µm RP18

Gradient:  5 to 55% MeCN/0.1% TFA in 30 min.

..and also larger polypeptides such as the 60 amino acid bovine Insulin that is chromatographed isocratically with good peak shape. Normally only chromatographed with gradients.

Sample: Bovine Insulin.   

Column: 150 x 4.6 mm Exsil Paragon 5 µm RP18

Eluent: 32% MeCN/0.1% TFA @ 1 ml/min.           

Exsil Paragon  delivers conventional selectivity with all the Exsil benefits

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