4. 
The methylene chloride extract was concentrated 
directly to 5 ml using the Rotovap followed by a 
stream of nitrogen. No solvent extraction step 
was needed. 
The results of the various extraction tests are as 
follows: 
Test 1 
A comparison of the efficiency of ultrasonication 
and Soxhlet extraction is shown in Table 14. Ultrasonication 
extracted greater amounts of phthalates than Soxhlet extraction 
from the same sediment collected at the mouth of the Chester 
River. The incompleteness of the Soxhlet method is believed to 
be the result of the lower eddy diffusion of solvent in the com¬ 
pacted solid sediment. With particular regard to the time course 
study, it is felt that the present experiments give a sound 
basis to reject the Soxhlet technique on the basis of its 
greater proneness to contamination, its incompleteness and the 
high cost associated with slow rate and need for laborious re¬ 
petition . 
Test 2_ 
A second and more stringent test of the sonication 
technique was carried out. Sonicated material was rinsed free 
of retained extracting liquid, and the samples were then 
subjected to re-extraction. The results are shown in Table 15. 
The repeated use in test 26 of sonication drew a 
blank—no evidence for further extraction was observed. Es¬ 
sentially the same finding was observed when the sonicated 
sample was washed free and then subjected to Soxhlet extraction. 
Test 3 
A comparison was made of wet Soxhlet and dry sonica- 
tive extraction of Tenneco Pond sediment. In general, these 
more heavily polluted samples of sediment seemed to be more 
easily extracted so that is not a stringent test. 
Analysis of the Internal Standards --The use of dimethoxyethyl 
phthalate (DMEP) seemed ideal in the sense that its gas chromato¬ 
graphic elution time fit into a window that caused no inter¬ 
ference with the DBP or DEHP measurements. Further, its 
chemistry was parallel to that of the other phthalate esters. 
However, we eventually became aware that our procedural blank 
levels were significant: 0.10 + 0.04 (n=6) ppm for DBP and 
0.28 + 0.22 (n=3) ppm for DEHP. Direct analysis of the DMEP 
standard revealed the cause since it contained 4 percent DBP and 
11 percent DEHP! These are not serious interferences since the 
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