The importance of purging the sample for the removal of CO2
was demonstrated by treating pure water samples differently.
There was no distinct difference in the measured 12C+ intensity
for bidistilled water samples (distilled in a quartz apparatus) and
those which were additionally acidified by nitric acid. Also, the
storage of these water samples in glass or PE bottles shows no
significant effect. On the other hand, a reduction of the carbon
concentration by a factor of about 2 was obtained for an acidified
and helium-purged water sample. Additional reductions of the
carbon blank by a factor of about 1.5 could be achieved by using
water purified with a Millipore system equipped with a special
filter for the absorption of organic material. The use of such a
largely carbon-free water as an eluent in SEC separation is
essential for DOC determinations in chromatographic fractions.