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The new easy way forward

Kromasil® EternityXT is a family of unparalleled stationary phases that keep you in the forefront of purification technology. The Kromasil® EternityXT bulk materials support you in your preparative chromatography needs even under extreme harsh conditions where the mechanical and chemical stability of the packing could be challenged.

Designed for extended lifetime

The well regarded EternityXT family of products is based on patented technology where the material can operate under extremely demanding conditions, including extended pH range and clean-in-place conditions normally used for polymer based materials. Kromasil® EternityXT stationary phases can be used beyond the pH window of Kromasil® Classic materials, recognized for their mechanical and chemical stability for a variety of applications worldwide.

Key benefits with Kromasil® Eternity

The Kromasil® EternityXT family of stationary phases

Kromasil® EternityXT is the chemically stable merged organic/inorganic silica material of choice for the purification of pharmaceuticals, peptides and oligonucleotides under reversed phase preparative chromatography.

This reinforced silica has extraordinary high chemical stability, maintains the benefits of the well-recognized Kromasil® Classic silica and offers first-rate separation power as well as loadability at low, medium and high pH from impurity isolation to full scale purification manufacturing.

Kromasil® EternityXT bulk materials are end capped and are shipped in both C18 and C8 derivatizations providing the flexibility needed from small to large scale preparative chromatography.

Main platform characteristics
Pore size100 Å
Particle sizes1.8, 2.5, 5 and 10 μm
Surface area310 Å
This platform is fully scalable.
Kromasil® EternityXT 10 μm derivatizations for purification
TypeCarbon contentconditions' pH range
C1819 %1 - 12
C813 %1 - 12
The operating pH range for both Kromasil® EternityXT C18 and C8 are the same.
Usable pH range for silica based materials

Chemical stability equal to none.

With Kromasil® EternityXT C18 and C8 you have stationary phase options to purify main compounds and isolate impurities depending on sample hydrophobicity and you can operate freely through practically the entire pH range. As a significant portion of the API purified today are basic in nature it is possible to run under strong basic conditions with these phases to increase loading onto the column, improve productivity and therefore reduce overall purification costs. Other compounds such as peptides and oligonucleaotides can also benefit from high pH purification methods.

Separation of Angiotensins at high pH

Separation of Angiotensins on Kromasil® EternityXT C18
Increased selectivity for peptides at high pH
Angiotensin II (1046.18 Da):
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe
Angiotensin III (931.09 Da):
Arg-Val-Tyr-Ile-His-Pro-Phe.
  • Conditions
  • column: Kromasil EternityXT-10-C18, 4.6 x 250 mm
  • Flow rate: 1.0 ml/min
  • Low pH
  • Mobile phase: acetonitrile / water / 0.1% TFA
  • Gradient: 0 min: 9%, 30 min: 35% acetonitrile
  • Detection: UV @ 220 nm
  • Temperature: 30 °C
  • Low pH
  • Mobile phase: acetonitrile / water + 0.1% NH4OH
  • Gradient: 0-5 min: 5%, 35 min: 26.5% acetonitrile
  • Detection: UV @ 225 nm
  • Prep injection: 40 mg mix of angiotensins II and III

State-of-the-art stability

Testing for mechanical and chemical stability is one of the cornerstones in the development of Kromasil® stationary phases. The Kromasil® EternityXT materials for preparative chromatography have been designed to specific requirements where the packed material has been exposed to various hydrolysis and clean-in-place conditions.

Long-term chemical stability

In the following figures the long-term chemical stability at low and high pH is shown.

Low pH conditions simulate very long-term use by applying an elevated temperature of 80 °C, and a highly aqueous mobile phase, 95% water, with 0.1% TFA (trifluoroacetic acid), pH ≈ 1.9. The EternityXT materials still show excellent stability, with very low shift in k’ over time.

High pH conditions include highly aqueous bicarbonate buffer at pH 10.5, at an elevated temperature of 60 °C. It has been shown that bicarbonate buffer is especially aggressive when used with silica-based packing materials, but it has little effect on the retention factor for EternityXT, due to the very dense derivatization and EternityXT platform, protecting the silica matrix.

Stability test at low pH
Stability test at high pH
Stability test legend
  • Conditions
  • Column size: 4.6 x 250 mm
  • Acidic hydrolysis
  • Mobile phase: methanol / water / trifluoroacetic acid (5/95/0.1), pH ≈ 1.9
  • Flow rate: 0.2 ml/min
  • Temperature: 80 °C
  • Basic hydrolysis
  • Mobile phase: acetonitrile / 10 mm ammonium carbonate, pH 10.5 (10/90)
  • Flow rate: 0.2 ml/min
  • Temperature: 60 °C
  • Chromatographic test conditions
  • Mobile phase: acetonitrile / water (70/30)
  • Test substance: phenanthrene
  • Flow rate: 1 ml/min
  • Detection: UV @ 254 nm

Chemical stability - CIP conditions

It is possible for you to sanitize or regenerate Kromasil® EternityXT C18 and C8 in-column (CIP) even at 1 M NaOH, if you so require. Kromasil® EternityXT stationary phases are disruptive in the marketplace as 1 M NaOH is a standard in biochromatography for treatment of polymer resins and now this barrier has been minimized between polymer and silica based materials due to the characteristics of the Kromasil® EternityXT platform.

CIP test results
The figure shows the leakage of silicon during after a number of CIP cycles at different NaOH concentrations. At 0.1 M NaOH, even Kromasil® Classic resists better than regular competitors. Already at 0.5 M NaOH, the main hybrid 10-C18 competitor shows serious leakage, actually higher than EternityXT phases at 1 M NaOH.
  • Conditions
  • Column size: 4.6 x 250 mm
  • Mobile phase: 10 column volumes of NaOH solution/ethanol (50/50)
  • Flow rate: 1 ml/min, for 10 column volumes (contact time 41.5 min)
  • Test substance: nortriptyline at pH 7.0
  • Temperature: ambient

Chromatographic performance
– EternityXT vs polymeric packing

It is well known that PS/DVB-based packing materials exhibit very high chemical stability at high pH, allowing cleaning steps involving for example 1 M NaOH. However, the material can unfortunately not compete with silica-based packing materials in terms of chromatographic performance.

With Kromasil® EternityXT it is now possible to obtain the high separation power associated with silica-based materials, and at the same time experience very high chemical stability at high pH.

Stability that matches a polymeric material
The graph shows a typical comparison between a silica- and a polymer-based packing material: Kromasil® EternityXT and the market leader for PS/DVB-based packings, where identical conditions have been used. The chromatogram shows a preparative separation of insulin, where it can be seen that the silica-based material, EternityXT, has markedly sharper peaks, with roughly only 50% of the band broadening seen on the PS/DVB-based material. Both analytical efficiency and loading capacity is significantly better for EternityXT.
With Kromasil® EternityXT it is possible to obtain the high separation power associated with silica-based materials, and at the same time experience very high chemical stability at high pH, as can be seen in the figures.
  • Conditions
  • Column size: 4.6 x 250 mm
  • Mobile phase: ethanol / ammonium acetate, 0.2 mM
  • Gradient: for EternityXT; 0 min: 30%, 60 min: 38% ethanol
  •   for PS/DVB; 0 min: 34%, 60 min: 42% ethanol
  • Flow rate: 0.7 ml/min
  • Temperature: 25 °C
  • Detection: UV @ 280 nm

Preparative separation with Kromasil® EternityXT C8

Separation of capsaicins on EternityXT C8 (alt)
  • Conditions
  • Column size: 4.6 x 250 mm
  • Mobile phase: ethanol / ammonium acetate, 0.2 mM
  • Gradient: for EternityXT; 0 min: 30%, 60 min: 38% ethanol
  •   for PS/DVB; 0 min: 34%, 60 min: 42% ethanol
  • Flow rate: 0.7 ml/min
  • Temperature: 25 °C
  • Detection: UV @ 280 nm