PARTICULATE ORGANIC MATTER IN SEA WATER
5
this can cause serious errors. Scrubbing and rinsing with isopropyl
alcohol are recommended.
Various kinds of filters have been used in this work. For purposes
of microscopic examination Millipore filters ars commonly used. A sea
water sample of 50-250 ml is filtered ; the pad is then dried and cleared
and mounted with cedar oil or Permount. Scrupulous cleanliness is
required. All glassware should be rinsed with isopropyl alcohol immediately prior to use, and distilled water or any stains used in the
preparation should be pre-filtered. Most distilled water supplies contain considerable quantities of organic matter which can be converted,
on standing, into flake-like particles indistinguishable from some of the
materials naturally occurring in sea water. The type of work done by
Gordon (1970a), using histochemical stains to characterize the kinds of
particles found in the sea, requires fairly extensive treatment with
reagents and rinses. He found it necessary to monitor the operation
by running frequent reagent blanks and correcting his counts, if
necessary, for the presence of any extraneous particles.
Millipore filters also have been used frequently for any purpose
requiring the water to be freed of filterable particles. Various pore
sizes have been used, ranging from 0.22-5 p. If the filtered water is to
be used for experimental purposes, the filter should be pre-rinsed.
Glass fibre and more recently silver filters have been used to collect
material for measurements of total carbon or any other analysis requiring a filter that is relatively free of organic matter. Actually
neither type is ideal. They contain carbon that cannot be entirely
removed by baking a t the relatively low temperatures that they can
tolerate (about 40O0C), and in some cases baking has produced an
undesirable increase in the pore size of silver filters. Experience has
shown that 0.8 p silver filters contain less carbon than most of the
others, and they may be used without baking. However, there is
enough variation from one batch to another so that blank determinations on each batch are necessary, and fairly large water samples
should be used in order to minimize errors due to variability of the
blanks.
Silver filters, like the Millipore filters, have the advantage of graded
pore size, whereas the glass fibre filters have pores of varying sizes.
However, the writer has found no marked difference in the total catch
obtained by a fine glass filter as compared with 0.46 p silver filters, nor
did Gordon (1969) obtain significant differences when he filtered
aliquots of sea water samples through silver filters of different pore
sizes.
Sheldon and Sutcliffe (1969) examined this situation further, using
5
this can cause serious errors. Scrubbing and rinsing with isopropyl
alcohol are recommended.
Various kinds of filters have been used in this work. For purposes
of microscopic examination Millipore filters ars commonly used. A sea
water sample of 50-250 ml is filtered ; the pad is then dried and cleared
and mounted with cedar oil or Permount. Scrupulous cleanliness is
required. All glassware should be rinsed with isopropyl alcohol immediately prior to use, and distilled water or any stains used in the
preparation should be pre-filtered. Most distilled water supplies contain considerable quantities of organic matter which can be converted,
on standing, into flake-like particles indistinguishable from some of the
materials naturally occurring in sea water. The type of work done by
Gordon (1970a), using histochemical stains to characterize the kinds of
particles found in the sea, requires fairly extensive treatment with
reagents and rinses. He found it necessary to monitor the operation
by running frequent reagent blanks and correcting his counts, if
necessary, for the presence of any extraneous particles.
Millipore filters also have been used frequently for any purpose
requiring the water to be freed of filterable particles. Various pore
sizes have been used, ranging from 0.22-5 p. If the filtered water is to
be used for experimental purposes, the filter should be pre-rinsed.
Glass fibre and more recently silver filters have been used to collect
material for measurements of total carbon or any other analysis requiring a filter that is relatively free of organic matter. Actually
neither type is ideal. They contain carbon that cannot be entirely
removed by baking a t the relatively low temperatures that they can
tolerate (about 40O0C), and in some cases baking has produced an
undesirable increase in the pore size of silver filters. Experience has
shown that 0.8 p silver filters contain less carbon than most of the
others, and they may be used without baking. However, there is
enough variation from one batch to another so that blank determinations on each batch are necessary, and fairly large water samples
should be used in order to minimize errors due to variability of the
blanks.
Silver filters, like the Millipore filters, have the advantage of graded
pore size, whereas the glass fibre filters have pores of varying sizes.
However, the writer has found no marked difference in the total catch
obtained by a fine glass filter as compared with 0.46 p silver filters, nor
did Gordon (1969) obtain significant differences when he filtered
aliquots of sea water samples through silver filters of different pore
sizes.
Sheldon and Sutcliffe (1969) examined this situation further, using