The ability of your spectrophotometer to resolve absorbtion
lines is the basis of its theory of operation. If absorbtion
lines can not be resolved adequately, then interfering lines
will be integrated with the correct line, thus giving an
inaccurate measurement.

Benzene vapor is an effective material for the detection of
a defraction grating base spectrophotometer's resolving power
as it has a great number of close but distinct absorbtion lines.
Benzene vapor will not work well with a photodiode array
spectrophotometer as they do not measure a continuum and the
peaks will not be resolved well enough to be useable.

Set your spectrophotometer to a slit width and a scan rate
and make a note of the settings. Scan from 260 to 250 nm
which is the area of the largest peaks. Compare the peaks to
the scans below:

Compare the peaks from your spectrophotometer to the two graphs
shown above and determine what changes need to be made
to the settings of your spectrophotometer to improve the
resolution of your scan. Continue to alter both the slit width and the
scan rate until you have optimized the resolution. Make a note of
the settings and use them as the basis of your quality procedures. By counting
the resolvable peaks from your scan you will be able to determine if the resolution
of your instrument matches the specification for resolution
in your instrument user handbook.

Each time that the scan is repeated you can compare the new scan
with the previous scans to check for any variance. If your
instrument needs service because of a change in resolution,
the historical data will greatly assist the service technician.