Reference data from the NIH/EPA library, recently published by 
the National Bureau of Standards, strengthened the assignment 
of DEHP. 
DEHP was subsequently distinguished from DNOP by their g.c. 
retention times and mass spectra. There was no DNOP detected in 
the Chester River sediment. The use of glass capillary GCMS 
permitted a clear distinction (see p. 69) . 
Tests of the Methodology Based on GC/MS 
A series of experiments were carried out in order to 
validate the method. Preliminary experiments showed that de¬ 
sorption of DEHP or DBP occurred more efficiently from dry 
rather than wet sediment. Very few wet extractions were 
carried out thereafter. 
Rate of Extraction— 
A series of extractions by dichloromethane of the dry work¬ 
ing standard "R" (see Figure 7) were carried out. The DBP 
extraction was independent of the time given to the sonication 
step which was varied from 30 seconds to 4 hours. The results 
are shown in Table 11. The results show no apparent trend with 
time of sonication. Other experiments confirmed the finding 
TABLE 11. EFFECT OF SONICATION ON DBP EXTRACTION BY CE y Cl ? 
FROM SAMPLE "R" Z Z 
Sonication 
Time (min) 
> 
DBP Measurement 
(ppm)* 
0.5 
0.785 * 
5.0 
0 . 
725, 0.66 
30.0 
0.75 
120.0 
0 . 
79, 0.715 
Average Value 
0.74+0.02 (+ SDM, n = 6) 
Standard 
Deviation 
0.05 
Standard Deviation of Mean 
0.02 
Internal 
Standard: 
d-10-Anthracene 
These preliminary results are to be used on the basis of their 
relative accuracy. Subsequent determinations of absolute DBP 
levels were found to be more accurate. 
62 
