Wavelength repeatability

The temperature tuning coefficient of TeOa is 0.025 nm/°C, so it is clear that in order to combat the effects of thermal heating of the crystal due to incident optical and aconstic power, as well as environmental considerations, a good level of thermal control is needed. This can be in the form of a thermo-electrically cooled enclosure. This will deal to a certain extent with the need to achieve analyzer wavelength repeatability. However, it does not address the issue of wavelength reproducibility between AOTF modnles, which impacts the transportability of calibrations and datasets between analyzers. 

Checking for wavelength repeatability by using one or more suitable standards (e.g. polystyrene or rare-earth oxides). The repeatability of measurements should be consistent with the spectrophotometer specification. 

Robustness for UV-Vis Analysis. Wavelength accuracy, wavelength repeatability, diluting solvent (i.e., pH, concentration), solution stability, and bubble formation by the sipper can be investigated during validation of the analytical component. 

This figure also shows the potential for using CD as a tool for kinetic analysis. The Cotton effect at 289 nm is due to the concentration of free ketone present. The dimethyl ketal absorbs at much shorter wavelength. Repeated additions of small amounts of water shifts the ketone-ketal equilibrium toward the free ketone, which increases the value of the experimental molecular ellipticity. The formation of ketal also depends upon the structure of the alcohol, as well as on stereochemical factors. Thus cholestan-3-one gives 96% of dimethyl ketal, 84% of diethyl ketal and only 25% of the diisopropyl ketal. The proportion of ketal formed from the 3-keto-5 P- steroids is higher than in the case of their 5 a isomer. 

Wavelength repeatability is a measure of the precision of wavelength measured. The bandwidth refers to the width of an emission band (from the monochromator) at half peak height. This value, normally provided by the manufacturer is accepted. Using a mercury vapor lamp one can also check the spectral width. A number of well defined emission lines at 243.7, 364.9, 404.5, 435.8, 546.1, 576.9, and 579 nm can be used to check spectral bandwidth. However, the accuracy of the absorbance measured is dependent on the ratio of spectral bandwidth to the normal bandwidth (NEW) of the absorbing species. Most active pharmaceutical compounds have a normal bandwidth of approximately... 

Wavelength repeatability is a measure of the precision of the wavelength measured. 

Wavelength repeatability (A,) is the precision with which a spectrometer can make repeated measurements at the same nominal wavelength over tempo-... 

Cannes advantage. The intrinsic wavelength scale in an FT-NIR spectrometer provides wavelength repeatability better than one part in a million. The wave number scale of an FT-NIR spectrometer is derived from a HeNe laser that acts as an internal reference for each scan. The wave number of this laser is known very accurately and is very stable. As a result, the wave number calibration of interferometers is much more precise. If a calibration standard such as the NIST standard reference material SRM1920 is used, the wave number calibration is more accurate and has much better long-term stability than the calibration of dispersive instruments. 

Besides the speed and efficiency of wavelength selection, the acousto-optical tunable spectrometers (AOTS) are much smaller than grating monochromators with equal resolution. In a properly engineered design the long-term wavelength repeatability also surpasses that of the grating monochromators. 

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