User manual

Section 3- Applications
- The shorter pathlength is advantageous for highly concentrated samples. Although this is an automatic
function in other applications, the user does have the option of using the auto pathlength feature or
restricting the pedestal to a 1 mm pathlength in the UV-Vis application. In either case, the absorbance data
will be displayed as 1 mm equivalent absorbance values.
• Baseline Correction - allows for specification of a wavelength for the bichromatic normalization of
absorbance data for the entire spectrum. The baseline is automatically set to the absorbance value of the
sample at the reference wavelength. All wavelength data will be referenced off of this value. The default
wavelength is 750 nm. If the baseline correction is not utilized, the spectra may be offset from the baseline.
• Add Wavelength - adds cursor wavelength and cursor absorbance to the table. After a sample is
measured, move the crosshair to the wavelength of interest and click Add Wavelength to add to the table.
Alternatively, simply enter a wavelength in the highlighted field.
• Clear Wavelength – clears one entry from the wavelength table.
• Clear All – clears all entries from the wavelength table.
As with other applications, right-clicking within the graph display box generates a multi-option menu box. In the UV-
VIS application, an additional Sample labels on/off option is available. The Sample labels option either shows or
hides the absorbance values displayed at each selected wavelength. Right-clicking on a label allows editing,
color/font changes, rotation, send to back/front and deletion.
Making UV-Vis Measurements
1. Select the UV-Vis application from the main menu. If the wavelength verification window appears, ensure
the arm is down and click OK.
2. A default wavelength of 750 nm is automatically used for a bichromatic normalization. Select an alternative
reference wavelength or choose not to have the spectrum normalized by deselecting the Baseline
correction box.
3. Enter up to 40 wavelengths to monitor in the nm - Add wavelength(s) box. Select the first row, enter the
wavelength and click Enter. The next row will now be highlighted and additional wavelengths can be added
as above. Alternatively, wavelengths can be added by positioning the crosshair cursor on the desired
wavelength and clicking Add Wavelength. There are also optional buttons to clear one or all wavelengths.
- Select the file drop-down option Use current settings as default as a convenient way to limit set-up time
for each new workbook.
4. Select Add to report to include all measurements in the current report. The default setting is for all samples
to be added to reports. The Add to report checkbox must be selected prior to a measurement to save the
sample data to a workbook.
5. Select Overlay spectra to display multiple spectra at one time.
6. Establish a blank using the appropriate buffer. The blank solution generally is the buffer that the molecule of
interest is suspended or dissolved in. This solution should be the same pH and of a similar ionic strength as
the sample solution.
- Pedestal Option: Pipette 1-2 µL of the appropriate blanking solution onto the bottom pedestal, lower the
arm and click Blank.
- Cuvette Option (Model 2000c only): Insert the cuvette noting the direction of the light path indicated by
the etched arrow. The optical beam (2 mm) is directed 8.5 mm above the bottom of the cuvette. Refer to
the cuvette manufacturer for volume recommendations.
Note: The arm must be down for all measurements, including those made with cuvettes. It is
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