At Pittcon® 2011, most new
products appeared to be evolutionary,
not revolutionary.
Possibly, the recession sapped
money for innovation and hence fewer
new products resulted. But the meeting
was successful: The consensus of the vendors
was uniformly positive about the buying
interest of conferees. The quality of
leads was rated as good to high. I heard two
“best ever”s—all very positive signs for the
industry. The recession was bad in general,
but this industry segment has seen much
worse, especially in the 1970s and ’80s.
There were interesting developments this
year. Seven new supercritical fluid chromatography (SFC) instruments were introduced.
It’s been 30 years since there was
this much commercial interest in SFC.
In fact, there were decades when the new
product flow was next to zero. GC-time-of-flight (TOF)-MS attracted significant
attention. The mass analyzers are fast and
hence compatible with the fastest chromatographic
separations.
Tectonic-like industry consolidation is
the third major development. It has many
facets, depending on the situation of the
stakeholder: Employees fear for their jobs
since new owners often consolidate operations.
Customers are also concerned about
layoffs that may adversely impact instruments
and support teams. Ultimately, users
need reassurance that customer service,
including tech support, will not suffer.
This is especially important as the sophistication
gap between the vendors and users
widens. Some instruments are like high powered
sports cars—They have powerful
engines, but require experienced drivers.
After all, society demands and values the
results of our technology. But to maintain
credibility and value, analysts must deliver
accurate results. “Spinouts” can be deadly.
Chromatography
By all accounts 2011 was a very good year
for LECO (St. Joseph, MI). The firm
celebrated 75 years in business, and at
Pittcon tied for the Gold Editors’ Award
for the Citius™ LC-HRT (High Resolution
TOFMS). The LC is from Agilent
(Santa Clara, CA) and potentially other
vendors. The mass analyzer is LECO’s
Folded Flight Path™ design, where the
resolution increases as more traverses are
added to the flight path. The HRT comes
in both an LC and GC version. The TOF
analyzer is a briefcase-size box that contains
five hollow aluminum rectangles on each
end. These generate the gridless electric
field that most would call a reflectron but
that LECO calls a “mirror.” Between the
two mirrors is another piece of aluminum
with large vertical slots. These are called
the periodic ion lenses, and they direct the
ion beam from the source to the mirror and
then to the other mirror. Two passes provide
low-resolution TOF, which is useful in
GC. High resolution of high mass number
requires 8, 16, or 32 cycles. LECO claims
the gridless feature is responsible for the
high yield of ions. About 75% of incoming
ions are detected in one example; 90%
are detected in another. Reduced ion loss
explains the improved detection limit of
1 pg. Other specs are impressive: resolution
is 100,000 FWHM, mass accuracy is
<1 ppm, and acquisition rate is 200 spectra
per sec. (For a review of the Pittcon Editors’
Awards, see Hunt, J. Pittcon® 2011 Editors’
Awards: A Two-Way Tie for the Gold
Award. Am. Lab. 2011, 43(5), 4–6.)
Seven new SFCs! Who and why?
SFC showed surprising strength at Pittcon
2011, with seven instrument introductions
plus a host of columns. After 30 years, market
interest has reawakened from sort of a
Rip Van Winkle slumber. Early Monday
morning, the first product highlighted in the
Waters (Milford, MA) press conference was
the ACQUITY UPSFC™, which enables
the analytical chromatographer to reduce
the cost of analysis by up to 99%. Most of
this can be attributed to the reduction in
cost of the mobile phase. Food-grade CO2
is about $1.5/lb compared to at least $50/lb
for reversed-phase liquid chromatography
(RPLC) eluents. Even HPLC-grade water is
about $20/lb. Food-grade CO2 is sufficiently
pure for SFC since the CO2 is purified as it
is distilled from the cylinder into the pump
head. Run times in SFC are reduced by
90% due to the lower viscosity and greatly
improved mass transfer. The baseline noise
of the diode array detector (DAD) is less
than 10 uAU, which is good enough that
analytes at the 0.01% level can be detected
confidently. Interestingly, the Pmax of the
UPSFC is 6000 psi, which is only 40% of
the Pmax of other ACQUITY® UPLC instruments.
However, the low viscosity of SFC
mobile phases and the short columns reduce
the need for higher pressure.
Pumping SFC eluents, including CO2, is
much more difficult than most LC mobile
phases such as water, acetonitrile, and methanol.
CO2 is a liquid with a significant vapor
pressure at room temperature. If it is cooled
and compressed too much, it will form a
solid, aka dry ice. The ACQUITY UPSFC
uses Peltier cooling elements attached to
the pump heads to cool and hence liquefy
the CO2 so that it works in metering pumps.
This approach has traditionally been difficult
to implement since the flow rates were
higher. But UPLC is usually performed with
2-mm-i.d. columns or smaller, which flow at
about 250 μL/min. Peltier cooling appears to
be adequate. Waters also developed a new
line of UPLC columns specifically for SFC
called Viridis™ columns.
Aurora SFC (Redwood City, CA) and
Selerity Technologies Inc. (Salt Lake
City, UT) both introduced SFC modules
designed to convert a legacy HPLC to
SFC. This allows the chromatographer to
explore the efficacy of SFC with only a
modest investment in instrumentation,
assuming, of course, that one has a gradient
HPLC sitting idle. One requirement
is that the CO2 be conditioned to pump
well, and another is that the backpressure
needs to be controlled. The Aurora SFC
Fusion™ A5 is designed to sit to the left
of an Agilent 1100 or 1200 dual-pump gradient HPLC, and needs only 12 in. of
bench space. CO2 is supplied to the A5 as
a vapor at 40–60 bar. This is de facto distillation
of the mobile phase, which helps
purify it. Thus, food-grade CO2 is usually
sufficient for UV detection. This may not
be sufficient, however, if flame ionization
detection (FID) for hydrocarbons is contemplated.
The A5 has a condenser and
booster pump to manage SFC compressibility.
Pumps on the HPLC meter the
flow. After the column and detector, the
A5 also controls the system pressure.
Selerity’s 5000 Super Critical Fluid Pumping
Module was designed in collaboration with
the Research Institute for Chromatography
(Kortrijk, Belgium) to expand HPLC instruments
into SFC. Speed and cost are major
benefits, but sometimes selectivity is also different.
Selerity is the leader in characterizing
fuels by hydrocarbon type. The 5000
contains both cooling and heating zones plus
a backpressure regulator to control the retention.
It operates from 80 to 400 bar with a
flow of 0.5 to 10 mL/min. The system uses a
small electronic pressure regulator, like the
SFC Fusion A5, but a spokesperson for Selerity
says she prefers a long capillary tube on
the outlet of the detector to add a bit of pressure
to keep the mobile phase condensed.
Bubbles in the detector are unwelcome. Of
course, long capillaries worked well in HPLC
before degassers and helium sparging became
the norm.
Sepiatec (Berlin, Germany) introduced two
new SFC systems. The Sepmatix 8× Parallel
SFC is designed for rapid analytical
screening of stationary phases and run conditions
(primarily temperature, density, and
% modifier). Crossing chiral analytes with
suitable chiral stationary phases (CSPs)
is largely empirical, and many CSPs exist.
The columns work in parallel simultaneously,
which saves time. A chiral column
screening wizard displays thumbnails of
up to 80 chromatograms simultaneously.
Simple inspection leads to quick selection
of the most favorable candidates. The fluidics
of the Sepmatix involves two metering
pumps (for CO2 and modifier). After the
mixer, an electronic valve distributes the
flow to the eight independent flow paths. A
multiplexed DAD records each chromatogram.
Although it was not shown at the
meeting, the company also makes a compact
eight-column HPLC analyzer fed by an
eight-channel autosampler. This seems to
raise the possibility of adding an autosampler
and converting the Sepmatix SFC to a
very high-throughput SFC analyzer.
On a larger scale, Sepiatec introduced the
compact Prep SFC operating at flow rates
of 100 mL/min. This should be adequate
for columns as large as 30 mm i.d. Prep
SFC of chiral compounds has a huge cost
advantage, plus reduced concern about
residual solvents. Those concerned about
residual methanol can try ethanol. Pmax is
300 bar, which should be more than adequate.
The system pressure is controlled
with a fast electronic valve. Detection is
with a UV/VIS detector with λ range of
190–740 nm.