Optical rotatory dispersion
Complimentary and related to CD is the measurement of optical rotatory dispersion (ORD). This technique provides information on chiral molecules even without chromophores such as saccharides. It can be used to measure the chirality of non-absorbing samples and the determination of absolute configuration.
JASCO offers two methods of ORD detection: optical null and intensity measurement systems. The intensity measurement method, using a fixed analyzer, is simpler and more economical, while the optical null approach, with its rotating analyzer, is intrinsically more accurate because the measurement is absolute. Because ORD is very sensitive to the effect of strain in the sample cell window cylindrical cells are strongly recommended for use ORD measurement.
ORDM-520 ORD unit
This accessory allows detection of ORD over a wide angular range (90°) with very high accuracy using a rotating analyzer. No calibration is required, and switching back and forth from CD to ORD is handled automatically by the PC software. The system uses a separate optical path with servo-driven analyzer and a dedicated PM tube.
ORDE-521 ORD unit
The electrical ORD accessory has an angular range up to 2°. Since the measurement principle is based on an electrical measurement method, the apparatus is simpler and is also able to respond faster to changes in ORD signals.
Diffuse-reflectance CD
Samples that are insoluble or may change conformation when in solution have traditionally been difficult to characterize by CD. Diffuse reflectance, using an integrating sphere, is an effective way to analyze these samples, often dispersed into a finely ground scattering matrix such as KBr powder. In addition, diffuse transmission measurements of pellets or films are easily accomplished with the same integrating sphere, substantially increasing the collection efficiency for scattering samples and providing a suitable alternative to conventional transmission measurements.
DRCD-574 | DRCD attachment
The DRCD-574 unit utilizes a BaSO4 interior for economical reflectance and transmittance measurements.
DRCD-575 | DRCD attachment
The DRCD-575 offers a Spectralon™ interior as well as N2 purge port for improved performance at low wavelengths.
Spectralon™ is a trademark of Labsphere inc.