HALO® column packings are not made the typical way. Instead, the particles packed into HALO columns are manufactured using Fused-Core® particle technology that was specially developed to deliver hyper-fast chromatographic separations while avoiding the reliability issues so often associated with fast HPLC (Figure 1). Quick Link to: HALO RP-Amide  |  HALO HILIC HALO Phenyl-Hexyl

The ability of HALO to generate hyper-fast separations comes not only from their small particle size (2.7 µm) but also from the unique Fused-Core particle technology that creates a 0.5 µm porous shell fused to a solid core particle. As mobile phase flow rate is increased to speed-up a separation, the slow mass transfer of solute molecules inside the particles limits resolving power. Fused-Core particle technology addresses this limitation by providing an incredibly small path (0.5 µm) for diffusion of solutes into and out of the stationary phase, thereby reducing the time solute molecules spend inside the particles and minimizing a major barrier to fast chromatographic separations (Figure 2).

HALO columns deliver over 50% more separating power (theoretical plates) than a column of the same length packed with 3.5 µm particles and more than twice the plates of a column packed with 5 µm particles (Figure 3).

And, because of Fused-Core particle technology, HALO columns maintain their resolving power at high flow rates. This means that shorter columns and higher flow rates can be used to achieve remarkably fast high resolution separations (Figure 4).

Packing HPLC columns can be as much art as it is science. There are many variables that have to be optimized in order to pack a column well for even non-high throughput applications. But, the demands placed upon columns used in high speed applications, i.e., high flow rate and high pressure, make it especially difficult to pack a column that will hold-up for a satisfactory period of time. HALO particles facilitate the packing process in two ways. First, the unique Fused-Core® particle technology produces particles that have extremely narrow size distribution. Second, these particles are significantly more dense than conventional totally porous particles, allowing them to be more easily packed into stable and efficient columns. This combination of extremely narrow particle size distribution and very dense particles allows the production of columns that are incredibly rugged and reliable, as well as very reproducible from column to column (Figure 5).

Also of importance, the extremely narrow particle size distribution permits the use of 2 µm porosity inlet frits on the HALO columns. This is the same inlet frit porosity typically found on columns packed with 5 µm particles. The result is a column capable of delivering incredibly high sample throughput, much higher than 3 µm packed columns, but with the ease of use and durability of a column packed with 5 µm particles (Figure 6).

Who says you can’t have both high speed and ruggedness? HALO delivers both.

Fused-Core^® particle technology produces hyper-fast columns that can be used on practically all HPLC systems. Figure 7 provides a comparison of system back pressure for the HALO column versus other fast HPLC columns. Columns packed with stationary phases smaller than 2 µm often require pressures in excess of what is achievable with typical HPLC instrumentation. A very real bonus that comes with using a HALO column is that expensive ultra-high pressure instrumentation does not have to be purchased and new laboratory protocols do not have to be developed. HALO columns can turn almost any HPLC system into a high speed workhorse for your lab.

The well known van Deemter equation identifies the three main sources of band broadening.



The value of the A term, eddy diffusion, reflects the multiple flow paths through a column. Packing particle size, particle size distribution, and the uniformity of the packed bed all determine the value of A. Because of the high density and extremely narrow size distribution of Fused-Core particles, HPLC columns can be packed with well ordered beds that have A term values significantly smaller than what is typically seen with columns packed with totally porous particles. This is one of the reasons that HALO columns deliver column plate numbers that are much higher than what would normally be expected from their particle size.

The C term of the van Deemter equation, the coefficient of mass transfer, reflects the time it takes for analyte to diffuse in and out of the stationary phase. The C term is directly related to mobile phase velocity because higher velocity interferes with the equilibrium between the analyte, mobile phase, and stationary phase. The longer the path an analyte has to travel within the pores of the stationary phase support particles, the more detrimental will be the effect ofmobile phase velocity on column efficiency.

The path a solute has to travel within the pores of a stationary phase support particle can be reduced by using smaller size particles and this is typically the strategy that is used by column manufacturers when making columns for fast HPLC. Smaller particles have shorter diffusion path lengths and, therefore, are less affected by increases in mobile phase velocity. HALO particles, by virtue of their 0.5 μm porous shell, have reduced the diffusional mass transfer path by one third compared to 3 μm particles. As the molecular size of the solute increases, its diffusion rate slows, making this effect even greater. The result is a column that can achieve faster separations and higher sample throughput.

HALO stationary phases are made using ultra-pure reagents and "Type B" silica. The peak shapes for bases and acids are excellent on HALO columns because metal contamination has been virtually eliminated and interference from silanol groups has been minimized (Figure 9). Because of the elimination of “secondary retention” of solutes from metal contamination or silanol interaction, column-to-column reproducibility is also excellent.

Stationary Phase Support Ultra-pure, “Type B” silica 1.7 µm solid core particle with a 0.5 µm porous silica layer fused to the surface 150 m2/gram surface area 90 Å pore size Bonded Phase Monomeric bonding chemistry Densely bonded phase Maximized endcapping C18: Octadecyldimethylsilane, 3.5 µmoles/m2 C8: Octyldimethylsilane, 3.7 µmoles/m2 pH Range: 2 to 9 Maximum Pressure: 9,000 psi, 600 Bar

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