Drinking Water Monitoring - The Drinking Water - page 194

TAble 10.4
Recommended Sample Storage and Preservation Techniques

Maximum Storage
Time (Recommended/
Regulatory)

Container
Type Test Factor Preservation

Alkalinity P, G Refrigerate 24 hours/14 days

BOD P, G Refrigerate 6 hours/48 hours

Conductivity P, G Refrigerate 28 days/28 days

Hardness P, G Lower pH to <2 6 months/6 months

Nitrate P, G Analyze immediately 48 hours/48 hours

Nitrite P, G Analyze immediately None/48 hours

Odor G Analyze immediately 6 hours/NR

Oxygen, dissolved
Electrode G Analyze immediately 0.5 hour/STAT

Winkler G Fix immediately 8 hours/8 hours

pH P, G Analyze immediately 2 hours/STAT

Phosphate G(A) Filter immediately; refrigerate 48 hours/NR

Salinity G, wax seal Analyze immediately or use

wax seal

6 months/NR

Temperature P, G Analyze immediately STAT/STAT

Turbidity P, G Analyze same day or store in

dark up to 24 hr; refrigerate

24 hours/48 hours

Source: Adapted from APHA, Standard Methods for Examination of Water and Wastewater ,
American Public Health Association, Washington, DC, 2005.
Note: P = plastic (polyethylene or equivalent); G = glass; G(A) = glass rinsed with 1 + 1 HNO 3 ;
Refrigerate = store at 4°C in dark; NR = none recommended; STAT = no storage allowed.

(APHA, 2005) , or those specified by the laboratory that will eventually pro-
cess the samples (see Table 10.4 ). In general, handle the sample in a way that
does not cause changes in biological activity, physical alterations, or chemical
reactions. Cool the sample to reduce biological and chemical reactions. Store
in darkness to suspend photosynthesis. Fill the sample container completely
to prevent the loss of dissolved gases. Metal cations such as iron and lead and
suspended particles may adsorb onto container surfaces during storage.
References used for sampling and testing must correspond to those listed
in the most current federal regulations. For the majority of tests, to com-
pare the results of either different water quality monitors or the same moni-
tors over the course of time requires some form of standardization of the
methods. The American Public Health Association (APHA) recognized this
requirement when, in 1899, it appointed a committee to draw up standard
procedures for the analysis of water. The report (published in 1905) con-
stituted the first edition of what is now known as Standard Methods for the
Examination of Water and Wastewater , or Standard Methods. This topic serves
as the primary reference for water testing methods and as the basis for most
USEPA-approved methods.