46
When the proper program is displayed, press
ENTER. Unless the instrument
is already adjusted to the correct wavelength, the instrument prompts for
the correct wavelength value; for example:
Adjust the wavelength control until the nanometer (nm) readout matches
the prompted value. Always approach the desired wavelength from the
high side for best accuracy and repeatability. When the values are the
same, the prompt will change to
Zero Sample, followed by the program’s
units and chemical form (see section
3.3.3 Zeroing the Spectrophotometer).
Note: If the wavelength is not set properly according to the programmed
wavelength, the wavelength number in the display will flash. You may, however,
perform the test with an alternate wavelength by pressing the
ENTER
key when the
alternate value is in the display. The nanometer display will continue to flash,
indicating the recommended wavelength is not being used.
3.3.2 Sample Preparation
The zero solution (or blank) is usually prepared at this time. The blank for
a specific procedure can be a variety of solutions:
• Sample being tested without the reagents
• Sample with reagents and a masking agent added
• Deionized water
• Deionized water with reagents added (a reagent blank)
Generally, sample preparation consists of adding the contents of a
premeasured reagent pillow(s) to 10 or 25 mL of the sample. Follow the
instructions in the Procedures Manual.
It is important to observe the waiting period specified in the particular test
procedure to be certain that the color (due to the reaction of the reagent
with the substance being measured) develops fully. Many procedures also
give a maximum time limit after which the color may begin to fade.
The DR/2010 Spectrophotometer has color development times programmed
into the method software. The operator is notified by a series of short beeps
when the time has elapsed. The timer must be initiated by pressing
SHIFT
TIMER
at the time the countdown should begin.
nm
+8.8.:8.8.
ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ
888500
*P272
Dial nm to 590
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