Attention:

Certain features of Sigma-Aldrich.com will be down for maintenance the evening of Friday August 18th starting at 8:00 pm CDT until Saturday August 19th at 12:01 pm CDT.   Please note that you still have telephone and email access to our local offices. We apologize for any inconvenience.

Ascentis Express Guards: Efficient and Effective Protection for all HPLC and UHPLC Columns

By: Craig Aurand, Reporter US Volume 28.4

Craig Aurand
craig.aurand@sial.com

The new Ascentis Express Guard Cartridge system provides significant improvements in column lifetime of any HPLC column, including classic particles, sub-2 μm UHPLC, and newer technology superficially porous particles, without sacrificing resolution or throughput. The efficiency permits their use as an analytical column, directly connecting to MS interfaces.

Protecting any HPLC Column is Important

Using guard columns is recommended to protect your HPLC column investment. Guards extend column life by providing chemical and mechanical protection from contaminants entering the system from the sample, the mobile phase, and instrument wear. The ideal guard column design provides this protection without sacrificing performance or throughput.

back to top

Why sub-2 μm HPLC Columns Foul Easily

Recent significant advances in HPLC have evolved around new particle technologies and enabling instrumentation. Sub-2 μm or UHPLC particles have garnered attention in the past decade because of the high column efficiencies and rapid separations they can provide. Although the advantages of sub-2 μm particles have been largely supplanted by the Fused-Core® particle technology behind Ascentis Express, they are still quite common. Many users have found that a significant drawback to sub-2 μm particles is their tendency to foul, which leads to high pressure and lost resolution. The broad particle size distribution of sub-2 μm particles requires 0.5 μm frits; this is the reason UHPLC columns foul so readily.

back to top

New Ascentis Express HPLC Guard Column

Users of any HPLC columns, whether packed with conventional HPLC particles, the sub-2 μm UHPLC particles discussed above, or the Ascentis Express Fused-Core or other superficially-porous particles, can realize significant improvements in column lifetime without sacrificing resolution or throughput by using the new Ascentis Express guards. In terms of theoretical plates per meter (N/m), these guards provide values comparable to Ascentis Express analytical columns, but add only seconds to the analysis time.

back to top

Effective for Column Protection and Stand-alone Performance

A demonstration of the performance of the Ascentis Express guards is shown in Figure 1. Methadone and two metabolites were separated on a 5 cm x 2.1 mm I.D. Ascentis Express analytical column with and without a 0.5 cm x 2.1mm I.D. Ascentis Express guard column. Comparison of the top and middle chromatograms show that the Ascentis Express guard column actually increased the total number of plates in the system by nearly 3,000, but added only 20 seconds and 37 bar. The Ascentis Express guard column actually has enough plates to serve as an analytical column. The bottom chromatogram shows the same separation with the guard column directly inserted into the MS interface as in Figure 2. Note the extremely rapid analysis (<20 seconds) and baseline resolution.

Figure 1. Efficient, Effective Column Protection with Ascentis Express Guard Columns
53911-U 53514-U

Figure 2. Ascentis Express Guard Connected Directly to MS Interface


back to top

Features and Benefits of Ascentis Express Guards

Four features lead to the efficiency benefits of Ascentis Express guards:

  • design provides zero-dead volume connections
  • auto-adjusting ferrule seating depth (prevents gaps)
  • low (<1.5 μL) total swept volume flow path (excluding the cartridge)
  • Ascentis Express Fused-Core (2.7 μm) packing material

back to top

Other important attributes:

  • finger-tight design for tool-free installation
  • rated to 15,000 psi (1,030 bar)
  • direct connection to any HPLC column or compatible threaded interface
  • economical, disposable cartridges for cost-effective protection

Ascentis Express guards can be used to protect any HPLC or UHPLC column, and also can serve on their own as a short analytical column for extremely rapid analysis. The product listing below contains the various phases currently available packed into the Ascentis Express guards, along with the hardware housing. The guards are supplied in packs of three cartridges. We also recommend using our high performance HPLC fittings with these and any HPLC columns.

back to top

Materials

     
Related Links