Hach DR/700 Procedures Manual page 244

LEAD,
continued
c) After two minutes the sample is ready for analysis. Steps 2 and 3 are
skipped in the analysis procedure. Use 100 mL of this preserved sample
directly in Step 7.
Sampling for lead contamination from drinking water sources such
as well water or water from main supply lines
a) Add 10 mL of pPb-1 Acid Preservative to a one-liter bottle.
b) Turn on the tap for 3-5 minutes or until the water temperature has
been stable for 3 minutes.
c) Collect exactly one liter of water into the bottle containing the acid
preservative.
d) Cap and invert several times to mix.
e) After two minutes the sample is ready for analysis. Steps 2 and 3 are
skipped in the analysis procedure.
Notes
a) At least one liter should be collected to obtain a representative
sample. If less than one liter is collected, use 1 mL of pPb-1 Acid
Preservative per 100 mL of sample.
b) If nitric acid is to be substituted for pPb-1 as a preservative or the
sample is digested, the buffering capacity of the pPb-2 Fixer Solution
may be exceeded. Adjust the sample pH to 6.7 to 7.1 pH with 5 N
sodium hydroxide after Step 4.
c) Each sample type typically requires different sampling procedures.
Consult with the appropriate regulatory agency in your area for more
information about your specific sampling requirements.
ACCURACY CHECK
Standard Additions Method
The standard additions method for checking the validity of the test
results can be performed as follows:
a) Use a TenSette Pipet to add 0.1 mL of a 10 mg/L Lead Standard
Solution (included in the reagent set) to a second 100-mL portion of the
sample.
48-8