and wavelength measurements can only be achieved if due consideration is
given to the resolution of the monochromator in use. In modern instruments
with grating monochromators, the resolution relates directly to the slitwidth
The smaller the slit and associated spectral bandwidth, the greater the
resolution, but the corresponding reduction in energy means the signal-to-noise
ratio falls. When measuring an absorbance band in a high-resolution instrument,
it is recommended that the spectral bandwidth (SBW) should not exceed 10%
of the natural bandwidth (NBW) of the band.
simple checks on the resolution power of a spectrophotometer will ensure,
for example that adjacent peaks will be fully resolved and not be blended
into a combination peak with the associated wavelength, and absorbance errors.
For the measurement and checking of this fundamental
parameter, Starna® offers you the choice of either a sealed liquid cell
(0.02% v/v solution of toluene in hexane), or a sealed benzene vapour cell.
formulation is described and used in the European Pharmacopoeia where
the ratio of the peak maximum at 269 nm to the minimum at 266 nm gives
a measure of the resolution of the instrument.
SBW (nm): 0.5 1.0 1.5 2.0 3.0
2.5 2.1 1.6 1.4 1.0
determinations are run against the hexane blank supplied with each
Reference Material, and the procedure is similar for all spectral
Scan the 265-270 nm region, and calculate the peak maxima and minima.
Calculate the peak/trough ratio and compare to the reference values
instrumental linearity is established using the Double Aperture method.
Primary instrumental wavelength calibration is established using the
emission lines from mercury and deuterium sources.
traceability links to NIST primary materials are established using
SRM 2034 holmium oxide (4% m/v) in perchloric acid (10% v/v), SRM
930e and SRM 1930 neutral density glass filters.
All appropriate fundamental parameters
and procedures relating to measurement, handling and storage are fully
documented on the certificate supplied with each Certified Reference