74 percent by desorbing with 1 ml of THF, or 75-80 percent if 
> 1.5 ml were used. The final procedure called for 2.5 ml of 
THF. Then 1.7 ml of purified water was added so that the 
liquid sample composition matched the initial HPLC carrier 
make up. The liquid chromatograph 254 nm UV monitor (Waters 
Model 440) remained on scale using 25 pi samples of extract. 
Similar tests were carried out using DTDP (ditridecyl- 
phthalate) and the results were quite similar except that a 
lower recovery, approximately 60 percent, was obtained. 
The precision of the HPLC results were found to be linear 
with the amount of added standard to within 5 percent variabil¬ 
ity. This was observed during Sep Pak adsorption of 10 ppm 
DEHP dissolved in water samples ranging from 30 to 150 ml in 
volume. 
Water analysis in Tenneco Pond and several sampling sites in 
the Chester River was attempted using C18-Sep Pak cartridges to 
concentrate the analyte. These cartridges were soon clogged by 
suspended particles so the sample volume was limited to 150 ml 
or less. GCMS showed that the liquid chromatographic (LC) 
technique alone in one instance gave an apparent but false 
identification of ditridecylphthalate. At trace concentrations, 
LC was considered valid for setting upper limits. 
The final conditions for HPLC analysis were obtained using 
a linear carrier gradient proceeding from 60 percent THF/40 
percent H 2 O to 90 percent/10 percent over a 5.0 minute period. 
A flow rate of 2.0 ml/min was used. 
Sediment extracts in dichloromethane were twice treated by 
adding THF and using purified nitrogen gas blowdown to remove 
the dichloromethane. Then makeup water was added, as before, 
to give the correct liquid solvent rates. 
Quantitative Analysis of Sediment Extract using GC/MS-SIM 
The Hewlett Packard 5992A GC/MS system was used for the 
analysis of sediment extracts. The microprocessor-controlled 
5992A uses a jet separator to interface the gas chromatograph 
to a hyperbolic quadrupole mass filter. A 3-foot (90 cm) 
silanized glass column (packed with 3 percent SE-30 on Chromo- 
sorb W-AW-DMCS) was used. The column was temperature program¬ 
med from 140°C-250°C at 5°/min. The system was later converted 
to a SE-52 glass capillary column programmed from 160°C-275°C 
at 7.5°/min. Up to 6 ions can be monitoring during a chromato¬ 
graphic run in the selected ion monitoring mode. The base peak 
of DEHP, m/z 149 was monitored. Mass 59 was also monitored 
which is characteristic of the internal standard, dimethoxyethyl 
phthalate (DMEP). DMEP has a low mass 149 abundance which de¬ 
creases its chromatographic interference with other possible 
54 
