7-1
7. KEY OPERATIONS IN SPECTRUM MODE
This chapter outlines the operating procedures for the SPECTRUM mode.
7.1 Outline
In addition to simultaneous monitoring of CD and UV chromatograms, the CD-1595 chiral
detector allows simultaneous CD and UV spectral measurements by stop-flow scanning.
Please note that this function is primarily meant to find the optimum wavelength for the
compound of interest to be monitored. In order for the detector to maximize the sensitivity,
a Hg-Xe lamp and a monochromator with a relatively wide spectral bandwidth (20nm) are
incorporated. Therefore, a spectrum obtained by a detector with this configuration has
limited accuracy to evaluate it qualitatively. For such purpose, please use CD
spectropolarimeter such as one from JASCO J-series products .
Spectral measurement is carried out by the single-beam method. This means that a
measured spectrum includes background spectra contributed by spectrometer
characteristics, mobile phase, etc. In order to obtain the true spectrum, such background
spectra must be subtracted from the measured spectrum that is known as baseline
correction. This is done by measuring the background first when no sample
is being
eluted, i.e., the baseline spectrum, then, the spectrum of the sample is measured. Finally,
the detector will output the true spectrum.
7.1.1
Principles of Operation
The following operations are performed in the SPECTRUM mode:
1) The baseline spectra (CD and UV) are acquired then stored into memory #10.
2) Spectra of sample compounds are measured and stored into memories #0-9.
3) Baseline correction is executed by subtracting the baseline spectrum from the
measured spectra. Spectra stored in the specified memory number are output as
baseline-corrected ones to the recorder or integrator output.
Steps 1), 2) and 3 are described in detail in Sections 7.2, 7.3 and 7.4, respectively.
(NOTE)
The baseline spectra are automatically stored into memory #10. Measuring new baseline
spectra delete the previously stored spectra.
7.1.2
Operation
SPECTRUM mode key operations are summarized below (refer to Fig. 7.1):
1) Change to SPECTRUM mode by pressing [SCAN].
2) Enter "0" and perss [EDIT/ENTER] after step 1) to select the baseline measurement
and baseline correction operations. Refer to Section 7.2.
3) Enter "1" and perss [EDIT/ENTER] after step 1) to select spectrum measurement.
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