152
800-356-1688 or 814-353-1300
HPLC COLUMNS
Physical Character ist ics
pH ranges and temperature limits: see product listings on pages listed here.
Column lifetime will be shorter when operating at pH and/or temperature extremes.
Managing High Backpressure
High backpressure is one of the most common problems encountered in HPLC analyses. Normal column backpressure is
observed after a new column has been installed and equilibrated with mobile phase. Unfortunately, this pressure often will
increase as the column is used because particles collect on the column inlet frit. These particles can be sample impurities,
mobile phase contaminants, or materials from the injector or autosampler rotor seal.
In addition to increasing backpressure, particles on the frit can cause split peaks, peak tailing, and, eventually, over-pressure
shut-down. In some circumstances, these problems can be corrected by back-flushing the column. However, in many cases the
result is an unusable column.
To minimize backpressure problems, all samples and mobile phase solvents must be filtered before use, and rotor seals should
be changed on a routine basis. Along with these preventive measures, it is advisable to use precolumn filters such as the
Trident guard column protection system, pages 196-198. Particles build up on the inexpensive, replaceable frit in the filter,
instead of on the permanent frit at the column inlet.
tech
tip
Applications
Carbon
load (%)
Pore
Size (Å)
End
Cap?
Restek
HPLC Column
Allure Biphenyl
Y
60
23
Multiple ring structure; excellent for aromatic and unsaturated compounds. Increased retention over
traditional phenyl phases.
Allure Silica
— 60
— Highly retentive phase for normal phase separation.
Ultra C18
Y
100
20
Ideal for anilines, barbiturates, carbonyls, fat-soluble vitamins, fatty acids, glycerides, phthalates, PTH amino acids,
steroids, other acids.
Ultra Aqueous C18
N
100
15
Ideal for analyses that require >90% water in the mobile phase. Excellent for highly water soluble
or poorly organic soluble compounds. Excellent for water-soluble vitamins and organic acids.
Ultra IBD
N
100
12
A polar group assists in deactivating surface silanols and contributes to unique separation selectivities for acids,
bases, zwitterions, and other polar compounds.
Ultra C8
Y
100
12 Selectivity and peak shape similar to Ultra C18, but less hydrophobic retention.
Ultra C4
Y
100
9 Ideal for peptides and small proteins.
Ultra C1
— 100
5
Alternative selectivity to Ultra C18 or C8 columns, especially for polar analytes. Shortest chain alkyl phase
available for reversed phase separations.
Ultra Cyano
Y
100
8 Excellent for basic pharmaceuticals, steroids (normal or reversed phase conditions), or other basic compounds.
Ultra Phenyl
Y
100
10 Ideal for fatty acids, polycyclic aromatic hydrocarbons, purines and pyrimidines, and polar aromatics.
Ultra Amino
N
100
2 Superior general purpose amino phase. Ideal for carbohydrates.
Ultra PFP
Y
100
7 Ideal for taxol and precursors, or halogenated compounds, amines, esters, or ketones.
Ultra Silica
— 100
— Ideal for normal phase applications.
Ultra Carbamate
— 100
— Rapid analysis of carbamates.
Ultra Quat
— 100
— Proprietary phase for the analysis of paraquat and diquat and other quaternary amines.
Viva Wide Pore C18
Y
300
9 Proteins and other higher molecular weight compounds.
Viva Wide Pore C8
Y
300
5 Proteins and other higher molecular weight compounds. Less retentive than C18 phase.
Viva Wide Pore C4
Y
300
3.5 Proteins and other higher molecular weight compounds. Less retentive than C18 and C8 phases.
Viva Wide Pore
Biphenyl
Y
300
6.7 Exhibits excellent peak shape for a wide range of compounds; ideal for large molecule and biomolecule assays.
Viva Wide Pore
PFP Propyl
Y
300
5
Exhibits excellent peak shape for a wide range of compounds, including nucleosides, nucleotides,
and halogenated compounds.
Viva Wide Pore Silica — 300
— Normal phase applications for highly retained high molecular weight compounds.
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Mar 2011
