GE MOA 280i, Руководство по эксплуатации и обслуживанию

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GE Analytical Instruments ©2006
12-10
DLM 14291 Rev. A
off”. If off-scale peaks are obtained for standards, the standard should not be
included in the calibration curve. There are three options for off-scaled peaks:
inject a smaller volume, dilute the sample or change the NOA’s sensitivity to Low.
The Low Sensitivity is 500 times less sensitive than High. The linear range for the
NOA for nitrite measurements will depend on how sharp the peaks are, but
typically the NOA has a linear response from the detection limit of ~1 picomole to
~400 picomoles in the High Sensitivity and ~0.1 nanomoles to 200-250 nanomoles in
the Low Sensitivity. In terms of concentration, 1 nM is 1 femtomole/µL, 1 µM is 1
picomole/µL, and 1 mM is 1 nanomole/µL. For a 100 µL injection, the linear range
is 10 nM to 4 µM for the High Sensitivity, For a 5 µL injection the linear range is 0.2
µM to 80 µM.
The NOAnalysis Liquid program will automatically multiply the signals collected in
the Low sensitivity by 500 to account for the difference in the PMT amplifier gain.
However, Sensitivity cannot be changed while collecting data with the Liquid
program and then have the program correct for the gain difference. Stop the
acquire program and collect data in either the High Sensitivity setting or the Low
Sensitivity setting.
Repeatability
The repeatability for nitrite measurements should be 5-10% depending on the
concentration of the samples and standards (lower repeatability will be obtained
for low concentration samples). If the repeatability is >5% or a linear response is
not achieved, identify the problem before analyzing the samples (see the
Troublshooting Chapter 16 for solutions to repeatability problems).
Nitrite Contamination
The most common problem, particularly for low level (<1 µM) nitrite measurement
is contamination. If the glassware, pipettes, and other equipment are
contaminated with nitrite, then the actual concentration of NO
2
-
in the standards
will be higher than expected. Rinse all equipment with nitrite-free deionized