Columns, chemicals, and consumables
(CCCs) account for more
than 30% of the chromatography
market. The quantities are
large. Globally, 400,000 active HPLCs
produce two 100-car tanker trains of waste
mobile phase per year. This cost nearly a
billion dollars to buy and a similar number
to dispose of. With an average of five
columns/year, the number of columns is
about two million. This seems low, since
a few chromatographs run 24 × 7 and use
hundreds of columns. Columns are a topic
close to the heart of many chemists, since
one can utilize one’s chemical training to
use and even improve them.
SFC columns
Since there was so much interest in supercritical fluid chromatography (SFC) instruments, let’s lead with columns for
SFC. SFC is often practiced with HPLC columns. This is successful, particularly
with chiral phases such as AD, OD, and
OJ. However, validated methods may look
better if they use columns mainly qualified
as SFC columns by the manufacturer.
YMC America (Allentown, PA) is on top
of the SFC explosion with the introduction
of 11 columns. Each is tested under
SFC conditions prior to shipment. Surface
chemistries are 2-ethylpyridine, diol (60
Å), N,N-diethylaminopropyl, pyridine,
amide, propylacetimide, silica, diol (120
Å), amino, cyano, PVA-sil, and polyamine
II. The columns are packed with
5-μm silica particles in 4.6 × 250 mm hardware.
YMC can also provide other column
lengths, diameters, and particle sizes by
special order.
Four new Viridis™ SFC columns were
displayed in the Waters (Milford, MA)
booth. Stationary phase chemistries include
2-ethylpyridine, 4-ethylpyridine, fluorophenyl,
and unbound BEH (ethylene bridged
hybrid particle). The particles are all 1.7 μm
in diameter, but can be scaled up to 5 μm
for preparative separations using the same
surface chemistry.
GreenSep™ columns from ES Industries
(West Berlin, NJ) are specifically optimized
and rated for SFC. GreenSep Amino
Phenyl is recommended for analytes containing
OH, COOH, and amines by SFC
without the use of additives. GreenSep
DEAP is noted for the excellent peak
shape of amine and amino analytes without
the use of peak shape enhancers in the
mobile phase. GreenSep Ethyl Pyridine
is also very effective in separating amino
analytes. GreenSep Nitro is the phase of
choice for isomers of aromatic analytes. If
the nitro column does not work, GreenSep
PFP has orthogonal selectivity. Hence,
if one is not suitable, another is. Finally,
GreenSep Pyridyl Amide provides good
loading capacity and unique selectivity.
Peak shape additives are seldom required.
In summary, ES offers six attractive phases
for SFC.
Recognizing the empirical nature of chiral
stationary phase selection, Regis Technologies
(Morton Grove, IL) has set up a
service for screening an analyte against its
library of chiral stationary phases (CSPs)
using SFC and HPLC. Thus far, 519 analytes
have been screened, and a 95% hit
rate has been obtained with HPLC. This
is similar to the success rate claimed by
high-performance capillary electrophoresis
(HPCE). The company also offers a similar
service for SFC. Regis is equipped with
Waters SFC 80 and 350 preparative SFCs,
plus two analytical SFC instruments.
The prep instruments can deliver mg to
kg quantities, depending on the project.
Obviously, this service would be very
attractive for exploration studies. SFC is
easy, but it is also different. Speaking from
experience, experience is useful.
HPLC columns
Agilent’s (Palo Alto, CA) acquisition
of Varian merged companies with
major product offerings in consumables.
Thus, it is not surprising that the
page count of the new catalog for chromatography
is now 1344 pages, a 50%
increase over last year. To be fair, the
new catalog also includes a few pages
of supplies for spectroscopy.
Update on core-shell particles and
columns
Stating in the late 1960s, core-shell
column packings (e.g., Zipax) have followed
a byzantine path to today’s editions.
These are optimized to enable
legacy HPLCs to better compete with
the ultrahigh-performance liquid chromatographs (UHPLCs), at least in speed,
as measured in peaks per second or total
run time. The story began with DuPont
Instruments (Wilmington, DE) and has
traveled through several hands to wind
up in Agilent’s today. Now several vendors
offer core-shell particles with a basic
design of a solid core of about 1.7 μm and
a porous 0.5-μm-thick outer shell. The
total particle diameter is thus about 2.7
μm. Columns packed with these particles
have been a commercial success primarily
due to improved run time offered to
users of conventional HPLC instruments.
Typical products include Poroshell
(Agilent),
Halo (Advanced Materials
Technology. [Newark, DE]), and Kinetex® (Phenomenex, Torrance, CA). The
newest is the SunShell core-shell packing
from ChromaNik Technologies (Osaka,
Japan) introduced at Pittcon® 2011. The
bead has a particle diameter of 2.6 μm,
which is 0.1 μm smaller than some traditional
ones.1
Agilent’s press package for Pittcon
2011 contained a chronological listing
of the important historical milestones
for Agilent
in chromatography. Interestingly,
the last entry, dated January
2011, was titled, “Agilent Secures Patent
for Porous Shell LC Particle Manufacturing
Technology.”
With good reason, some customers avoid
use of sole-sourced products. The claims
in the patent,1 which are the protected
points, appear to be limited to particles
that are agglomerated with urea-formaldehyde
polymer. The polymer is
removed by calcination. Thus, the fears
of sole-source scenarios are probably
unfounded. Further, the introduction
to the patent describes other synthetic
approaches, most of which use technology
that is already in the public domain. Agilent
has therefore provided a road map for
others to follow.
New column brands
Thermo Fisher Scientific (Waltham,
MA) introduced Syncronis silica-based
HPLC columns. The particles are either
1.7 or 5.0 spheres with 100-Å pore. The
5-μm particles are targeted for conventional
instruments, and the 1.7-μm are
reserved for UHPLC. The surface chemistry
range is C18, C8, AQ, and phenyl, with
others listed under the specialty phases
(Tables 1 and 2). All are end-capped. The
C18 phase has a high carbon load at 16%
C. The benzyalmine test shows low silanol
activity, which is expected for end-capped phases. No data were provided about column
lifetime. In summary, the Syncronis
columns appear to be competitive with
other premium brands. Thermo also introduced
the EASY-Column™ for nano-LC.
Columns are packed in metal-free, fused-silica
capillaries.
Table 1 - New columns for reversed-phase liquid chromatography (RPLC) (source: interviews and trade literature)
Table 2 - New specialty phase columns for LC (source: interviews and trade literature)
Agilent added a new series of columns,
ZORBAX Rapid Resolution High Definition
(RRHD) columns. These are built
on 1.8-μm silica particle and are rated to
18,000 psi. They are now available in eight
phases, including four C18 phases.
RPLC columns continue to dominate the
LC column space. This year, new products
appeared to be extensions in the available
phases to improve the choice in selectivity
(Table 1).
The Acclaim Carbamate (Dionex) is
designed to provide baseline separation of
all critical pairs in U.S. EPA Method 531.2
using linear solvent gradients. Bonding
is stable, giving exceptionally low bleed,
which is useful with MS detection. The
Acclaim RSLC 2.2 columns are designed
for labs that have huge sample loads.
Depending on the separation, throughput
can be increase 15× compared to conventional
HPLC. Plus the solvent per sample
is reduced by a similar factor. Dionex
also points out that the shorter columns
give sharper peaks, which can reduce the
amount of sample required by 60–85%.
The Pmax for 50-mm column length is 9000
psi; the 100-mm length is 12,000 psi. For
conventional HPLCs, Dionex offers the
same surface chemistry on 3-μm-diam silica,
also with a 120-Å pore. The Pmax is
4500 psi.