Safety - Hach DR/700 Procedures Manual

the test is performed. This is done by zeroing the instrument on
deionized water and reagents.
In most cases, the reagent blank is so small the instrument is zeroed on
either an untreated portion of the original water sample or deionized
water. This is done routinely without any significant loss of accuracy
except where extremely small amounts of a constituent are sought. In
such a case, it is best to determine the reagent blank by performing the
test on a sample of high-quality, turbidity-free deionized water. The
result is expressed in the concentration units of the test and is subtracted
from the test results of subsequent samples using that particular lot of
reagent. It is necessary to determine the reagent blank only at first use
and at intervals of several months unless subsequent contamination is
suspected.
Every effort is made to produce reagents with the lowest possible blank.
In most cases, it is less than 0.009 absorbance units. In some instances,
it is either impossible or not practical to produce reagents with such a
low blank. In these cases, it is best to determine the reagent blank as
explained above and subtract it from each determination. A note is
included in the appropriate procedures describing when this is
necessary.

Safety

Safety is the responsibility of each individual when performing analysis
procedures, and the analyst must develop and maintain good safety
habits. Because many of the procedures in this methods manual require
the use of potentially hazardous chemicals and apparatus, it is important
for the individual conducting them to minimize chances for accidents by
practicing good laboratory techniques. Several rules applying to water
analysis in the laboratory and in the field follow. They are not all
inclusive, but they emphasize practices that often are key factors in
personal injury incidents.
Read Labels Carefully: Each reagent label should be read carefully
with particular attention paid to the precautionary information. Never
remove the label from a reagent container while it contains reagent. Do
not put a different reagent into a labeled container without changing the
label. When preparing a reagent or standard solution, be sure to label
the container clearly.
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