Hach DR/700 Procedures Manual page 681

PHOSPHONATES,
7.
Insert the
ultraviolet (UV) lamp
into the prepared
sample. The other
sample is the blank.
Note: UV safety goggles
should be worn while
the lamp is on.
Note: Do no handle the
lamp surface.
Fingerprints will etch
the glass. Wipe lamp
clean with a soft, clean
tissue between samples.
Do not use phosphate
detergents to wash
glassware.
Note: A specially
designed cord adapter
(Cat. No. 19584-00) is
available for
performing two
digestions with a single
power supply. A second
UV lamp
(Cat. No. 20823-00) is
also required.
continued
10 minutes
8.
Turn the lamp on.
Wait for 10 minutes.
Note: Phosphonates are
converted to
orthophosphate in this
step.
Note: The digestion step
should normally be
completed in less than
ten minutes. However, a
contaminated sample or
a weak lamp could
result in incomplete
conversion to
phosphate. Check
conversion efficiency by
running a longer
digestion and seeing if
readings increase.
81-7
9.
Turn the UV lamp
off and remove from
the sample cell.