Circular Dichroism with an
Thirty millidegree CD signals in 16 milliseconds
was an achievement considered beyond
the realm of possibility until the
Olis RSM CD system was invented. Now, it is routine.
'Easy' CD measurements can be made in under
one second; hundreds of CD scans will
have been made and averaged during
this time. 'Difficult' measurements
will take multiple seconds; tens or
hundreds of thousands of CD scans
can be collected and fitted during
this time. With real-time data averaging
and a continuous presentation of the
improving spectrum on the screen,
the investigator has the option of
interrupting data collection as soon
as the data are sufficiently noise-free.
When a sample is not stable, conventional
CD technology systems (which take
minutes to collect a single scan)
cannot capture the true shape of the
CD spectrum, because the sample will
have changed from the start to the
end of the scan. The Olis RSM, collecting
full scans every millisecond, is much
more likely to collect the true spectrum
of an unstable CD sample. Any changes
to the sample which occur over time
will be captured by the RSM as a change
in the entire spectrum, not as a change
in the shape of the spectrum which
was caused by deterioration of the
sample over time that took place during
the minutes elapsed from the start
to the end of the scan.
Everyone interested in time-resolved CD
should use the RSM CD. Time-resolved
CD includes situations where the sample
is changing rapidly, as in flash photolysis
and stopped-flow mixing.
The scanning range of our UV/Vis model
is within 167 to 1150 nm, depending
upon gratings, detectors, and lamps
We recently optimized the system for complete
minimization of the effects of the
lamp instability on the signal, improving
sensitivity of CD detection to 10-
6 abs units.
DUAL BEAM ABSORBANCE AND
The Olis RSM CD collects absorbance scans
every millisecond while collecting
sub-second CD scans. As with other
configurations of the RSM, the scanned
range should be less than 300 nm (like
other configurations of the RSM, this
is a fixed slit width optical bench).
In order to obtain full spectral scans
(e.g., 167-1150 nm), shorter scans
will be made, saved, and then appended
one to the other ; or rapid-scanning
is turned off in favor of Conventional Speed Scanning.
The Olis RSM CD spectrophotometer requires
no calibration and uses no lock-in
amplifier. No longer must you fix
the amplitude of the CD signal based
on a standard like d-camphorsulfonic
acid, but you get the absolutely correct
answer in both sign and amplitude.
These details, along with others, mean
the system is easy to operate correctly.
Even novices to CD can obtain research
quality CD data.
A water cooled supracil 150 watt xenon
arc lamp is standard.?Other options
include 75 and 450 watt xenon arcs
lamps or tungsten/deuterium choices.?Wavelength
range you need will determine which
light source is best suited.
The CD system comes with one jacketed CD
cell holder, which can be used with
both a rectangular cell or a cylindrical
cell and two jacketed cell holders
for rectangular sample and reference
cuvettes for true dual beam absorbance
and single beam CD spectroscopy work.
This measurement can be made on the RSM
CD without additional expense.
Dramatic improvements happen often in out
efforts to distinguish this CD from
all predecessors. Please contact Olis
directly for the most comprehensive
and current information about "the
CD of the 21st century."
ACCESSORIES FOR USE WITH
Temperature-Controlled CD Cell Holder
Julabo F30-C Water Bath