Gschwend%20thesis.pdf

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For traps analyzed soon after loading, compounds boiling higher.
than about IOO C and lower than about 300 C, could be measured at the
ng/kg level and be seen well above background in the chromatograms.
The efficiency of stripping was assessed in a series of experiments
in which coastal seawater samples were spiked with known quantities of
a variety of compounds. For recovery experjJents at less than 50 ng/kg,
the water was prestripped, removed from the stripper, allowed to cool,
spiked and then analyzed. Table I-i shows the recoveries of these
compounds as compared to direct spikes of solvent containing the same
compounds on the traps. Nonpolar and highly volatile compounds were
recovered at greater than 80% efficiency. Slightly polar materials,
such as the aromatics, were stripped at lower efficiency. Relatively
polar substances such as the aldehydes were recovered poorly or not at
all. Higher-boiling compounds such as heptadecane were found at reduced
efficiency. Pentadecane recoveries at low spike levels appear enhanced
and this was probably due to relatively large concentrations still in
the seawater despite prestripping. A 50% recovery figure was probably
appropriate for pentadecane. No other evidence for nonlinearity of
recovery was seen within the 10-300 ng/kg range tested. Relative
variability of these recovery determinations was calculated to be
approximately 20%.
The standard deviation of the analysis of 21 samples from the
western Equatorial Atlantic for the l-chloro-n-decane internal standard
was + 20%. Other work on seawater samples collected in the coas tal
region near Woods Hole shows similar levels of reproducibility for other
compounds. Table 1-2 shows this result for an aromatic and an aldehydei
as well as for two internal standard chloro-alkanes.