Characterization of the
Microorganic Constituents of Water by
Instrumental Procedures
ROBERT A. BAKER, Senior Fellow
BERNARD A. MALO, Fellow
Mellon Institute
Pittsburgh,   Pennsylvania 15213
INTRODUCTION
Separation and identification of trace and microorganic contaminants is becoming increasingly important as investigators seek to understand and control
water quality. Recent advances in instrumental devices have lowered the detectable and measurable quantities necessary for direct analyses. Nevertheless, these
minimum analytical concentrations, usually mg/l, are still greater than those
which cause effects such as sensory, color or potential toxicological impairment.
Such effects may occur for organic concentrations of less than ug/1. For analyses,
preconcentration is requisite, but this step must not alter the structure or quantity
of individual organic constituents nor the relative distribution of components in
complex mixtures. The advantages and limitations of various concentration and
analytical procedures have been reviewed by Baker and Malo (1). Itis the objective of this paper to describe the application of selected combinations of concentration and analytical procedures, particularly those recently developed in this
laboratory, to the characterization of organics in actual field studies.
SAMPLING
Many presently employed sampling procedures utilize long sampling intervals
to accumulate sufficient material to permit subsequent analyses.
The longer the sampling time scale, the more likely is the possibility of missing short duration discharges. Analyses represent long term average rather than
instantaneous water quality conditions. It is desirable to avoid lengthy sampling
methods which are subject to biological or chemical degradation of constituents
or lead to selective adsorption-desorption problems on the collection media. Decisions regarding sample frequency, quantity, method of preservation if analyses
are delayed, and compositing must be tailored to individual situations. For example, if the purpose of the organic profile monitoring is to indicate sensory
quality characteristics, long-term or composite samples are of little value. Taste
and odor producing constituents often vary considerably over even short time intervals, volatiles may evolve, and continuing organic modification of natural
waters via biological activity is almost a certainty. Preservatives or fixing agents
may alter composition. Immediate separation of organic contaminants from spot
samples is the ideal practice. In field studies where sample numbers are often
restricted, a randomized sampling program of lower frequency will be potentially
superior to a rigid, fixed-time and number program. If the concentration procedure is conducted at the sampling site, not only is volume significantly reduced, but sample quality alteration is minimized. No concentration or analytical
procedure is universally suitable.    The most useful information will result from
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