Turner Designs TD-700, Руководство по эксплуатации

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TD-700 Laboratory Fluorometer Operating Manual
Page 31
For example, Rhodamine WT fluorescent dye provides linear readings from
about 10 parts per trillion to approximately 0.1 ppm. Using the 25 x 150
mm Sample Adaptor, linearity should be checked when measuring con-
centrations of dye higher than 0.1 ppm.
At dye concentrations below 0.1 ppm, a single-point calibration (one
standard and a blank) may be used to calibrate the TD-700. For concentra-
tions between 0.1 and 0.5 ppm, use a multi-point calibration with 3 to 5
different standard concentrations. Above 0.5 ppm, “concentration quench-
ing” occurs, and samples should be diluted into the linear range before
taking readings. Or, you can switch to a smaller size test tube or cuvette
(smaller pathlength) and increase the linear range.
Linearity may be checked by diluting a sample 1:1 or some other conve-
nient ratio. If it is linear, the reading will decrease in direct proportion to the
dilution. If the reading goes up (“concentration quenching”), you are beyond
the range for a calibration curve. If the reading does not decrease in direct
proportion to the dilution, you are in the range for a calibration curve, but
still beyond the linear range.
D. Temperature Considerations
Fluorescence is temperature sensitive. As the temperature of the sample
increases the fluorescence decreases. For greatest accuracy, read blank,
standard, and samples at the same temperature. (The TD-700 Fluorometer
does not compensate for temperature changes.) NOTE: The unit’s lamp
will heat samples if left in the instrument. Thus it is recommended that you
use the instrument’s Discrete Sample Averaging feature to ensure that
samples are read after they have been in the instrument for the same
period of time and are at approximately the same temperature.
Concentration
Fluorometer Reading
0
10
20
30
40
50
60
70
80
90
100
0 2 0 40 60 80 100 1 2 0 140 160 180
Linear Range
Range in which Multi-
Point Calibration is
n e e d e d
Concentration
Quenching is
Observed
Figure 1 . Linearity, Calibration Curve, and Quenching