above. Each vial was equilibrated at 30C for 24
(HPLC) system composed of the following compo-
nents:
minutes. The vial was then pressurized, forcing an
aliquot of the headspace into a 1-mL sampling
A Spectra Physics Model SP8810 precision iso-
loop. The loop was put in line with the carrier gas,
cratic pump.
thus transferring the sample to the head of the
A Spectra Physics Model Spectra 100 variable
chromatographic column (Restek MXT-1 mega-
bore [15 m 0.530 mm i.d.]). The column tempera-
wavelength UV detector set at 254 nm.
ture was maintained at 100C throughout the
A Dynatech LC-241 precision autosampler
entire run. The analytes were detected with a
equipped with a Rheodyne Model 7010A sam-
photoionization device operated with a source cur-
ple loop injector and a 100-L loop.
rent of 80 A. Chromatographic results were
An Alltech Model 3000 solvent recycling system.
reported as peak height measurements.
A Hewlett Packard Model HP3396 digital inte-
Calculations
grator equipped with a Hewlett Packard Model
Daily response factors were calculated as
HP9114B disk drive.
described above. The concentration of TCE in the
The autosampler was used to introduce samples
water samples was calculated by dividing the peak
by flushing the 100-L loop for 20 seconds at a rate
height response for the sample by the daily
of 0.5 mL/min. The phenol was separated on an
response factor
LC-18 (25 cm 4.6 mm i.d., 5 m) reversed-phase
[TCE]j = (peak height)j / (response factor) (1)
column (Supelco, Inc.) eluted with a binary eluent
of water and methanol (1:1, v/v) at a flow rate of 1.4
where (j) denotes each individual sample. This
mL/min. Chromatographic results were reported
resulted in a concentration value in the units of
as peak height measurements.
micrograms per liter in the water sample. Note
that, although the direct analysis was of the head-
Chemicals
space, the response factor was determined relative
The phenol used to prepare the analytical stan-
to the concentration of the water. This assumes that
dards was from Sigma-Aldrich. The analytical
the partitioning of the TCE between the water and
grade water in which the standards were prepared
headspace was equivalent for both the standards
was purified by a Milli-Q Type 1 Reagent Grade
and the samples; thus, the determination of the
Water System (Millipore Corporation). Methanol
concentration of TCE in the headspace can be alge-
used for the chromatographic eluent was from J.T.
braically factored out.
Baker.
The concentration of TCE in the clay samples
was calculated by determining the concentration in
Preparation of stock standard
the analyzed sample (j) using eq 1, then, with eq 2,
A stock standard of phenol was prepared by dis-
back-calculating to the concentration in the clay
solving 50 mg of phenol in reagent grade water and
using the dilution factor of 100 L to 10 mL from
diluting to 100 mL in a volumetric flask. The result-
the transfer of the aliquot of extract to the water in
ing concentration was 500 mg/L.
the vial, and the exact weight of the soil sample.
Initial calibration
[TCE]clay (g/g) =
For the initial calibration for the phenol analysis,
[(TCE)j (g/L)/0.81] (100) [0.004 (L)/w(g)]
a series of standards was prepared as a dilution of
the stock standard. Table 3 lists the details of the di-
(2)
lutions and the concentration of phenol in the cali-
where 0.81 = correction factor
bration solutions.
100 = dilution factor
0.004 L = combined volume of extract from
Table 3. Preparation and concentrations of
calibration solutions.
the four extractions
w = wet weight of the sample (g).
Calibration
Dilution from
Concentration
solution
stock standard
(mg/L)
Analysis for phenol
Stock standard
525.0
Solution 1
10:25
210.0
All of the analyses for phenol were performed
Solution 2
5:25
105.0
Solution 3
1:25
21.0
using a high performance liquid chromatographic
7
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