Troubleshooting TD-550/560 Oil in Water Analyzer
28 TD-550/560 Oil in Water Analyzer
Operation Manual
PN 106737
REV H
failure is a dirty optical surface or the cuvette adapter not being properly seated. Remove the cuvette
adapter carefully from the analyzer. Particles can be cleaned from the optical surface with canned gas
suitable for cleaning sensitive optical components. If a residue is present, gently clean the circular
optical surface with a lint-free laboratory tissue moistened with a small volume of 99% purity 2-propanol
(isopropanol or isopropyl alcohol). Do not use any other solvents or water. Do not spill liquid. Dry with a
second lint-free laboratory tissue. Repeat the test. If fail is still reported, please contact the appropriate
service representative for suggestions. There are no user-repairable components within the analyzer.
6.1 LOW FLUORESCENCE DURING CALIBRATION
The TD-550/560 does not impose a lower limit to the uorescence response of the calibration solution
as long as it is greater than the blank response. Benchmark International suggests that the minimum
uorescence response of the calibration solution should be 200 uorescence units greater than the
blank. Calibration that results in a calibration solution response difference less than 200 uorescence
units will cause excessive variation in the measurements. Should this happen, you should try
calibrating with a more sensitive channel (TD-560 only), a larger size cuvette, and/or higher calibration
concentration. The Deep UV channel on the TD-560 will be more sensitive than the Near UV channel for
most applications.
6.2 LINEARITY AND LINEARITY CHECKING
The linear range is the concentration range within which the readout of the TD-550/560 is directly
proportional to the concentration of the hydrocarbon. You must make sure the instrument is calibrated in
the linear range.
The linear range is dependent upon the sample cuvette size and the optical channel of the analyzer;
thus using a smaller cuvette size and/or changing the optical channel (TD-560) can extend the linear
range. See Section 2.2 Channel Selection guidelines and Section 2.3 Cuvette Selection Guidelines.
After performing a calibration, the linearity should always be checked to insure the calibration is within
the linear range. The linearity is checked by diluting the calibration solution exactly to half of its original
concentration with clean solvent in a clean container and then measuring the concentration. If the
measured concentration is much higher than the expected half concentration or even higher than the
original calibration solution concentration, this indicates non-linearity. Should non-linearity occur during
calibration, you should try using a less sensitive channel (TD-560 only), a smaller size cuvette, and/or
lower calibration concentration.
When measuring unknown samples, the sample extract should be checked for linearity by diluting
by a known volume with clean extraction solvent and then checking that the concentration reduction
corresponds to the dilution factor. If the reduction does not correspond to the dilution factor, then dilute
the extract with clean solvent until linearity is observed and then multiply the results by the nal dilution
factor.
6.3 MEASUREMENT OF SAMPLES CLOSE TO ZERO
For critical measurements, it may not be appropriate to report measurements close to zero without
taking into account minimum reporting concentrations. For approximate determination of the minimum
reporting concentration, Benchmark International recommends the following:
1. A calibration must rst be conducted and linearity validated.
2. Fill a cuvette ¾ full with clean solvent (FastHEX Method) or blank (No-Solvent Method).
3. Wipe the sides of the cuvette with a laboratory tissue and insert into the analyzer. Close the lid.
4. Press Read.
5. Remove the cuvette from the analyzer and then re-insert it. Close the lid.
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