3 • Operation and Maintenance
Doc. 065215-02 9/09
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3.10 Preparing Samples
NOTE Sample preparation can be performed while the system
is equilibrating.
3.10.1 Collecting and Storing
Collect samples in high density polyethylene 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 will 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
μ
m 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 changes in anion concentrations.
3.10.2 Pretreating
Analyze rainwater, drinking water, and air particulate leach solutions
directly with no sample preparation (other than filtering and possibly
diluting).
Filter groundwater and wastewater samples through 0.45
μ
m 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 printed installation instructions
provided with the inline filter.
Before injection, pretreat samples that may contain high concentrations of
interfering substances by putting them through Dionex OnGuard™
