bly is held in the mouth of a 22-mL glass vial. The
dilution that was required to bring the eluent into
plunger is depressed so that the mixture passes
the linear range of the initial calibration should be
through the SPE tube at about 5 mL/minute and
included in the calculations using the following
is collected in the glass vial. The acidacetone mix-
formula:
ture converts the retained picrate ions to unre-
g/g picric acid =
tained, protonated picric acid. The SPE tube and
daily rf (g/g-ABS unit)
filter are placed in a waste container.
[(Final ABS df) 0.5 (Initial ABS/df)]
11. A portion of the acidacetone eluent is trans-
ferred with a disposable pasteur pipet to a glass
spectrophotometer cuvette and the absorbance at
where rf is the response factor and df is the dilu-
400 nm measured and recorded as Initial ABS. The
tion factor.
spectrophotometer is zeroed with water.
12. The eluent is returned to the 22-mL glass
vial and the cuvette rinsed with water from a squirt
13. METHOD PERFORMANCE
bottle and discarded.
13. If the eluent has any color, a qualitative de-
The method has been applied to a series of soil
scription is recorded. A 5-mL aliquot of unacidified
samples whose picric acid concentrations had been
acetone plus a 5-mL aliquot of water is measured
determined by RP-HPLC (Table A2).
in a second 10-mL graduated cylinder and added
to the 22-mL vial. This converts any colorless, pro-
tonated picric acid to yellow picrate ions.
14. POLLUTION PREVENTION
14. A portion of the diluted eluent is transferred
to the cuvette using the same disposable pasteur
All containers of organic solvents and extrac-
pipet and the absorbance at 400 nm measured and
tion solutions should be kept capped to prevent
recorded as Final ABS.
evaporation. A bottle-top dispenser is highly rec-
15. If the Final ABS is greater than 0.7, the di-
ommended to prevent acetone spillage. Alterna-
luted eluent may be diluted further with water and
tively, a large, deep funnel may be used when mea-
remeasured.
suring the acetone into the 100-mL graduated
16. After measurement, the eluent is returned
cylinder. A large tray should be used under the
to the 22-mL vial and the pipet is placed in a waste
work area to contain any spilled solvents.
container.
17. The cuvette is rinsed, first with water from a
squirt bottle, then with acetone from a squirt bottle.
15. WASTE MANAGEMENT
It is critical that no residual water be present in
the cuvette when the next sample is added to the
All solid waste contaminated with solvents, acid
cuvette for the Initial ABS measurement. Water will
and extracted chemicals should be disposed of ac-
ionize any picric acid to picrate and invalidate the
cording to Federal, state and local regulations. This
background correction.
includes extraction bottles and soils, filters, syringes,
disposable pipets, SPE tubes and eluent vials.
All waste organic solvents from the extraction
procedures and rinses should be disposed of ac-
12. DATA ANALYSIS
cording to Federal, state and local regulations.
AND CALCULATIONS
All acidsolvent mixtures should be treated
The absorbance data are converted to picric acid
separately as required by Federal, state and local
concentration in the sample by the following for-
regulations.
mula:
g/g picric acid =
16. REFERENCE
daily response factor (g/gABS unit)
(Final ABS 0.5 Initial ABS).
Thorne, P.G. and T.F. Jenkins, "Development of
a Field Method for Ammonium Picrate and Picric
This is based on a 20-g wet-weight subsample ex-
Acid in Soil and Water," Special Report 95-20, USA
tracted with 100 mL of acetone and measured us-
Cold Regions Research and Engineering Labora-
ing the dilutions specified in the Procedure. Any
tory, Hanover, N.H.
16
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