Samples 
Oyster samples from the Chester River were collected July 2, 
1979 by personnel of the Chesapeake Biological Laboratory. The 
samples were frozen for subsequent delivery. They arrived in 
jars which had cracked presumably during the freezing process. 
The extent of possible contamination, however, was considered 
minimal. 
Oyster sample CBL-1 was collected at Buoy Rock correspond¬ 
ing to sediment site 1. Sample CBL-2 was from Spaniard Point 
where sediment sample 6 was collected. There is no equivalent 
sediment site for the CBL-3 sample collected at Ferry Bar. A 
fourth sample from Love Point contained too few oysters to 
analyze. A homogenate of seven commercial oysters from northern 
Chesapeake Bay was used for reference purposes. Unspiked sam¬ 
ples as well as samples spiked with DEP, DBP and DEHP were pre¬ 
pared from this. 
Results 
Oysters contain approximately 80 percent water and 2 percent 
lipid. Both of these tend to interfere with the analytical de¬ 
termination. The water must first be removed before considering 
extraction of the phthalates with methylene chloride. The lipid 
content is readily soluble in methylene chloride, as are the 
alkyl phthalates. An attempt was made to dry the oyster tissue 
using the same method successfully used for wet sediment. The 
tissue homogenate was spread as thin layer on a watch glass and 
placed in a desiccator containing sodium sulfate. This method 
was discarded because a bacterial bloom tended to form on sam¬ 
ples prepared in this way. However, the controls from commer¬ 
cial oysters were free from this mold-like growth. It is 
suspected that these oysters are thoroughly rinsed and an 
anti-bacterial preservative is added during processing. 
A more rapid drying method was needed. The preferred alter¬ 
native was lyophilization or "freeze-drying." Spiked and un¬ 
spiked controls were first freeze-dried to evaluate the method. 
The spiked samples contained 20 ppm each of DEP, DBP and DEHP. 
The extracts of these samples were injected directly into a 
glass capillary gas chromatograph with an FID detection. 
Numerous, partially resolved peaks resulted but the spiked peaks 
were not evident. GC-MS was used to identify the four major 
sets of peaks. The first large peak was identified by matching 
its mass spectrum to reference spectra as palmitoleic acid and 
closely related compounds that elute at 200°-203°C. The second 
large set of peaks eluting at 215°-217°C was identified oleic 
acid. The third (228°-232°C) and fourth (244°-248°C) groups are 
linoleic acid and linolenic acid, respectively. 
76 
