4• Startup
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4.3 Preparing Samples
This section provides basic information about collecting, storing, and preparing
samples for analysis.
NOTE Sample preparation can be performed while the system
is equilibrating.
4.3.1 Collecting and Storing Samples
Collect samples in high density polyethylene, polystyrene, or
polycarbonate containers that have been thoroughly cleaned with ASTM
Type I (18 megohm-cm) filtered and deionized water. Do not clean
containers with strong acids or detergents because these can leave traces
of ions on the container walls. The ions may interfere with the analysis.
If samples will not be analyzed on the day they are collected, filter them
through clean 0.45-micron filters immediately after collection; otherwise,
bacteria in the samples may cause the ionic concentrations to change over
time. Refrigerating the samples at 4
° C (39° F) will reduce, but not
eliminate, bacterial growth.
Analyze samples containing nitrite or sulfite as soon as possible. Nitrite
oxidizes to nitrate, and sulfite to sulfate, thus increasing the measured
concentrations of these ions in the sample. In general, samples that do not
contain nitrite or sulfite can be refrigerated for at least one week with no
significant change in anion concentration.
4.3.2 Pretreating Samples
Analyze rainwater, drinking water, and air particulate leach solutions
directly with no sample preparation (other than filtering and if required,
diluting).
Filter groundwater and wastewater samples through 0.45-micron filters
before injection, unless samples were filtered after collection.
A Dionex High Pressure Inline Filter (P/N 044105) is available for
removing particulates down to 0.45 micron from samples. Connect the
inline filter between the autosampler outlet and the sample inlet port on
the injection valve. For details, see the instructions provided with the
inline filter.
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