an aqueous sample, add the reagents to deionized water to prepare
the reagent blank. The prepared reagent blank includes only the
amount of color that is added to the deionized water by the reagent and
not the analyte. The prepared sample includes the amount of color that
is added by the reagent and the analyte.
For some chemistries, the intensity of the color decreases as the
analyte concentration increases. These chemistries are referred to as
bleaching chemistries because the measured sample is lighter in color
than the reagent blank that was used to zero the instrument. This
instrument is able to measure bleaching (or negative) absorbance
chemistries directly. Set the instrument zero with the reagent blank (the
most highly colored solution) and then read the sample or bleached
color directly.
Single wavelength procedure
Before starting
Always measure solutions in sample cells or AccuVac
®
Ampules. Do not put
the instrument in the sample or pour the sample into the cell holder.
Make sure that the sample cells are clean and there are no scratches where
the light passes through them.
Make sure that there are no fingerprints or liquid on the external surface of the
sample cells or AccuVac
®
Ampules. Wipe with a lint-free cloth.
Rinse the sample cell and cap with the sample three times before the sample
cell is filled.
Always insert the sample cell in the correct and consistent orientation so that
the results are more repeatable and precise. Refer to Figure 7.
Install the instrument cap over the cell holder before ZERO or READ is
pushed. Refer to Figure 8.
Measure the volume of the liquid reagent accurately. Use a pipet if possible.
If the test result is over-range, dilute a fresh sample with a known volume of
deionized water and repeat the test. Multiply the result by the dilution factor.
When the test is completed, immediately empty and rinse the prepared sample
cell. Rinse the sample cell and cap three times.
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