First Steps with the Fluorescence Detector 2
1100 Series FD Reference Manual 49
Multi wavelength detection
Time-programmed wavelength switching traditionally is used to achieve low
limits of detection and high selectivity in routine quantitative analysis. Such
switching is difficult
if compounds elute closely and require a change in excitation or emission
wavelength. Peaks can be distorted and quantitation made impossible if
wavelength switching occurs during the elution of a compound. Very often this
happens with complex matrices, influencing the retention of compounds.
In spectral mode, the Agilent 1100 Series FLD can acquire up to four different
signals simultaneously. All of them can be used for quantitative analysis.
Apart from complex matrices, this is advantageous when watching for
impurities at additional wavelengths. It is also advantageous for reaching low
limits of detection or increasing selectivity through optimum wavelength
settings at any time. The number of data points acquired per signal is reduced
and thus limits of detection may be higher, depending on the detector settings
compared to the signal mode.
PNA analysis, for example, can be performed with simultaneous multi
wavelength detection instead of wavelength-switching. With four different
wavelengths for emission, all 15 PNAs can be monitored (Figure 17 on
page 50).
Tabl e 10 Conditions for Figure 17 on page 50
Column Vydac, 2.1 x 250 mm, PNA, 5 µm
Mobile phase A = water; B = acetonitrile (50:50)
Gradient 3 minutes, 60%
14.5 minutes, 90%
22.5 minutes, 95%
Flow rate 0.4 ml/min
Column temperature 22
°C
Injection volume 2 µl
FLD settings PMT 12,
response time 4 s,
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