HALO® columns for UHPLC at "normal" pressure
compatible with UHPLC and conventional HPLC equipment

HALO® columns allow a fast separation as in UHPLC but at "normal" pressure under 400 bar on standard HPLC equipment.

The fast separation is achieved by smaller size particles packed into the column which reduces the diffusion of solutes into and out of the stationary phase and therefore reduces peak broadening. This allows faster flow rates, fast separations and higher sample throughput.

Unfortunately the smaller particles increase back pressure excessively and "fast" columns with 1.7 µm particles usually require expensive ultra-high pressure instrumentation.

The HALO® column is based on the Fused-Core particle technology.

A 0.5 μm porous shell is fused to a solid core particle of ø 1.7 µm. The shorter diffusion path of HALO® particles reduces axial dispersion of solutes and minimizes peak broadening. A HALO® particle has a diffusion path of only 0.5 μm compared to the approximately 1.5 μm diffusion path of a 3 μm totally porous particle.

This allows faster flow rate. Because of the increased separation power of the HALO® column, it can either be used for faster analysis or an improved separation.

The shorter diffusion path of HALO® reduces axial dispersion
 
The shorter diffusion path of HALO® particles reduces axial dispersion of solutes and minimizes peak broadening. Because of the shorter diffusion path, the performance advantages of HALO® become even more apparent when separating larger solute molecules and operating at faster mobile phase flow rates.
   

HALO® columns have a higher efficiency

Comparison of column back pressure

Van Deemter plots are a convenient way to compare the efficiency of HPLC columns. In this comparison we see that HALO® columns are more efficient than columns packed with totally porous particles and that they can be run at higher mobile phase linear velocity and still maintain their resolving power. Most HPLC systems have operating pressure limits of 400 bar or less. As the column packing particle size decreases, the column back pressure increases rapidly. To use columns packed with sub-2 μm size particles at their optimum flow rate, pressure that exceeds 6,000 psi is often encountered. This necessitates purchasing very expensive "ultra-pressure" equipment to achieve optimum performance. HALO® columns, even though they do generate slightly higher back pressure than columns packed with 3.5 μm particles, can be used with both UHPLC and conventional HPLC equipment.
   
Peak tailing due to trace metals or silanol groups is essentially non existent on HALO® stationary phases. The examples here show the excellent peak shape that can be achieved for either bases or acids when using a HALO® column. The conditions used for the bases were chosen to encourage any potential silanol interference. Note the excellent peak shape for amitriptyline under these conditions.

Sample:
1. Uracil
2. Butyl paraben
3. Propranolol
4. Naphtalene
5. Acenaphthene
6. Amitriptyline

Column: HALO® C8, 4.6 x 50 mm

Mobile Phase: 75% Methanol, 25% 25 mM Potassium Phosphate, pH 7.0

Flow Rate: 1.5 mL/Min

Temperature: ambient (24 °C)

Pressure: 3,000 psi, 205 bar

   

Quick Tips for Converting Conventional Reversed-Phase HPLC Separations to Ultra-Fast Separations

When applications from 5 µm Material are run on a HALO® Column the flow rate needs to be adjusted otherwise the back pressure increases too much. This Quick Tips Guide contains a conversion guide for adjusting the flow rate.

pdf 545 KB

   

HALO® UHPLC particle
• particle size 2.7 μm - a 0.5 μm thick porous layer is fused to a solid core
• Ultra-pure “Type B” Silica
• speric shaped
• pore size 90 Å
• surface area150 m2/gram

 

HALO® UHPLC column with C18 & C8 phase

Evaluation report on HALO® C18 columns - pdf 1.1 MB

Excellent performance for a broad range of analyte polarities. Separations are primarily due to hydrophobic interactions and differences in hydrophobicity among analytes.

C18 - will strongly retain polar and moderately polar analytes
C8 - provides similar selectivity to C18 but with less retention

   

HALO® UHPLC columns with Phenyl-Hexyl phase

Separations occur both due to hydrophobic and π-π interactions. Enhanced retention and selectivity for aromatic and unsaturated analytes especially those with electron withdrawing groups and halogens. Compatible with aqueous mobile phases.

   

HALO® UHPLC columns with RP-Amide phase

HALO® RP-Amide Phase for the separation of Analytes that form weak hydrogen bridges with Amide. This Phase is an alternative to C18 Phase for Analytes, when a C18 phase fails to provide an adequate separation. In general, acids will be retained more, bases will be retained slightly less, and neutral analytes will have approximately the same retention on the HALO® RP-Amide as they will on the HALO® C18.

   

HALO® UHPLC columns with PFP phase

UHPLC Trennung von polaren und nicht polaren Substanzen

Separations take place due to multiple types and degrees of analyte interactions including hydrophobic, π-π, dipole-dipole and hydrogen bonding. Can be used in the HILIC mode with mobile phases containing greater than 80% acetonitrile. Enhanced selectivity for stereoisomers. Compatible with highly aqueous mobile phases.

   

HALO® UHPLC columns with ES-CN phase

Provides strong dipole-dipole interactions with analytes and weak hydrophobic interactions. Suitable for use in reversed-phase, HILIC, and normal-phase modes. Rapid equilibration with low bleed for high throughput LC-MS applications. Extra stable bonding with sterically protected ligand provides improved stability and performance compared to conventional CN phases, especially at low pH (1–4).

   

HALO® UHPLC columns with Penta-Hilic phase

The Penta-HILIC is specifically designed and intended for hydrophilic interaction liquid chromatography, HILIC. The HALO® Penta-HILIC stationary phase is a highly polar ligand that possesses 5 hydroxyl groups tethered to the silica via novel proprietary linkage chemistry. The retention mechanism offered by the Penta-HILIC phase is a combination of hydrophilic interaction and weak hydrophobic binding interaction. Retention in HILIC mode as a function of mobile phase is opposite that of reversed phase. For example, increasing the mobile phase strength involves increasing the polarity of the mobile phase by increasing the aqueous component. Penta-HILIC is particularly recommended for the separation of highly polar analytes that are poorly retained in reversed phase mode. The Penta-HILIC phase is also recommended for LC-MS applications because of the MS friendly mobile phase conditions typically used with Penta-HILIC.

   

HALO® UHPLC columns with Hilic phase

The HILIC phase is an unbonded pure silica. It can be used for either normal-phase or HILIC mode of separation. When used in HILIC mode, it is recommended for similar applications as the Penta-HILIC phase described previously. Separations on HILIC are expected to be similar to Penta-HILIC, although subtle differences in selectivity will often occur, favouring one phase over the other when developing an optimized HILIC separation.

HALO® semi-preparative columns
pdf 62 KB

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