> Circular Dichroism wiht RSM1000

Circular Dichroism with an RSM-1000

 

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.

 

TIME-RESOLVED CD

 

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.

 

SCANNING RANGE

 

The scanning range of our UV/Vis model is within 167 to 1150 nm, depending upon gratings, detectors, and lamps used.

SENSITIVITY

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 CD SCANS

 

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.

 

CALIBRATION

 

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.

 

LIGHT SOURCE

 

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.

 

SAMPLE COMPARTMENT

 

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.

 

LINEAR DICHROISM

 

This measurement can be made on the RSM CD without additional expense.

 

FUTURE DEVELOPMENTS

 

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 RSM CD

 

Temperature-Controlled CD Cell Holder

Julabo F30-C Water Bath