Horiba Scientific FluoroMax-4 Operation Manual page 225

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FluoroMax -4 & FluoroMax -4P with USB rev. D (30 Jul 2012)
Reference detector
Resolution
Right-angle detection
Sample changer (auto-
mated)
Saturation
Scatter
Signal channel
Signal photomultiplier
Signal-to-noise ratio
S N
( / )
Single Point
beam is striking the sample properly.
The detector used to monitor the output of the xenon lamp. A silicon
photodiode with enhanced-UV response is used for the FluoroMax
and is connected to input channel R. Use S/R to correct for the xenon-
lamp response during an excitation scan.
The ability to separate two closely spaced peaks. Resolution can be
improved by decreasing the bandpass and the increment (step size).
Collection of fluorescence at 90° to the incident radiation. Right-angle
detection typically is selected for dilute and clear solutions.
An automated accessory that automatically positions up to four cu-
vettes held in the sample compartment. Use this accessory to run up to
four samples at one time for a small assay, or to run blanks with the
samples simultaneously. Automated sample changers are thermostatted
and possess magnetic stirrers.
The effect of having too much signal incident on a particular detector.
Saturated detectors give an erroneous result and no longer show any
response for small changes in signal. In some cases, saturation can
damage a detector's performance, so avoid saturation whenever possi-
ble. The R928P photomultiplier tube used on the FluoroMax
7
rates at 1 × 10 cps.
A combination of Raman, Rayleigh, and Rayleigh-Tyndall scattering,
which can distort fluorescence spectra with respect to intensities and
wavelengths.
See: Acquisition modes.
Detector used to measure excitation and fluorescence from the sample,
operated in photon-counting mode to provide the highest sensitivity.
Different detectors can be used to optimize different wavelength re-
gions.
The measurement of the signal observed divided by the noise compo-
nent seen in that signal. Generally, the better the S/N is, the better the
measurement is. This is accomplished by using photon-counting detec-
tion with the proper high-voltage bias for improved sensitivity during
fluorescence measurements. The user then optimizes the sample signal
to the higher area of the linear range for the detector, typically between
100 000 and 2 000 000 cps. Next, dark offsets or blank subtraction may
be used to improve the S/N. Finally, increasing the integration time or
repeating the same scan several times can improve the signal to noise.
For specifications, signal-to-noise may be represented as signal to
peak-to-peak noise, or signal-to-noise at first standard deviation (FSD).
The FluorEssence™ scan-type designed for performing single-point
13-9
Glossary
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-4,
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-4 satu-