3 • Operation and Maintenance
Doc. 031644-02 9/03
3-19
Sample Bandwidth
The sample bandwidth is the wavelength range at which the chromatogram is
measured. As the bandwidth increases, baseline noise decreases. Increasing the
bandwidth increases the number of wavelength signals overlaid at each point in
time. Increasing the bandwidth may also decrease the signal, especially of those
peaks with narrow peak maximas.
Select a sample bandwidth that provides the resolution required to achieve the
desired sensitivity. Selecting a wider bandwidth reduces baseline noise, but may
also reduce peak height. For narrow spectral peaks, select narrow bandwidths.
Example Chromatogram: Selecting the Bandwidth
Figure 3-4 illustrates how selecting a wide bandwidth for both the sample
and reference reduces noise by averaging over a wavelength range. The
operating conditions are:
Sample wavelength = 254 nm
Reference wavelength = Off
Flowing water at 1.0 mL/min, 10.35 MPa (1500 psi)
Figure 3-4. Effect of Sample Bandwidth on Baseline Noise
-0.0500
-0.0400
-0.0300
-0.0200
-0.0100
0.0000
0.0100
0.0200
0.0300
0.0400
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
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5.00
mAU
min
1
2
3
3
2
1
WVL:254 nm
Sample Bandwidth = 1
Noise = 26
µ
AU
Sample Bandwidth = 4
Noise = 16 AU
µ
Sample Bandwidth = 8
Noise = 14
µ
AU