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Day 7
.—Complete extraction 5; clean columns and system immediately.
(a)
Extraction 1
.—Adjust bath to maintain a temperature of 25 ± 1.0°C in columns and start
circulation pump (Figure
2015.15E
). Add 475 mL extraction solution to each flask. Pump
extraction solution and air from flasks to the bottom of the columns. Extract for exactly 2 h
after solution reaches test portion. Swirl flask occasionally to mix solution during extraction.
After 2 h, stop pump, reverse flow to top of column (Figure
2015.15F
); pump flows may be
accelerated to hasten transfer process. Pump air for 1 min after liquid is emptied from column to
ensure complete transfer of solution. Cool solution to 25.0°C, dilute to volume (500 mL) with
extraction solution, and mix. Transfer exactly 250 mL extract to a storage bottle; add exactly 5.0
mL stabilizing solution. Extracts should be stored frozen or analyzed within 21 days. Remainder
of test solution can be discarded. Extract 1 is ready for analysis.
(b)
Extraction 2
.—Immediately after completionof extraction No. 1, adjust bath to temperature X
(the bath temperature needed to maintain 50.0 ± 1.0°C in columns). Drain manifold to preheat all
manifold water. Start circulation to stabilize temperature in entire system 15 min before
beginning extraction 2. Do not circulate water more than 5 min prior to extraction 2. Begin
extraction 2 exactly 1 h after extraction 1 is complete. Add 475 mL extraction solution to
flasks. Pump extraction solution and air from the flasks at 4 mL/min to the bottom of columns
at predetermined time. Extract for exactly 2 h after solution first reaches samples. Swirl
occasionally tomixextract solutionduring extraction. After 2 h, stop pump, reverse flow to top of
columns, pumping solution back into flasks. Pump air for 1 min after all liquid is emptied to
ensure maximum transfer of solution. Cool extract to 20°C, dilute to volume with solution, and
mix. Using clean dry graduated cylinder, transfer exactly 250 mL of extract to amber HDPE
bottles, and add exactly 5.0 mL of stabilizing solution. Extract is now ready for analysis. Keep all
remaining 250 mL of solution in flasks to be used in next extraction. Add approximately 225 mL
of freshly prepared extraction solution to flasks, bringing total volume to approximately 475 mL.
(c)
Extraction 3
.—Immediately after completion of extraction No. 2, adjust bath to temperature Y
(the bath temperature needed to maintain 55.0 ± 1.0°C in columns). Drain manifold to preheat
all manifold water. Start circulation to stabilize temperature in entire system 15 min before
beginning extraction 2. Do not circulate water more than 5 min prior to extraction 3. Begin
extraction 3 exactly 1 h after extraction 2 is complete. Remainder of extraction 3 is identical to
No. 2 except extraction time is exactly 20 h.
(d)
Extraction 4
.—Immediately after completion of extraction No. 3 adjust bath to temperature Z
(the system temperature needed to maintain 60.0 ± 1.0°C in columns). One hour after completion
of extraction No. 3, begin extraction No. 4. Remainder of Extraction 4 is identical to No. 2 except
extraction time is exactly 50 h.
(e)
Extraction 5 (if needed)
.—One hour after completion of extraction No. 4, begin extraction
No. 5. Extraction No. 5 is identical to No. 4 except extraction time is exactly 94 h.
Following removal of test portion, clean columns in place with a large brush. If there is buildup or
Candidates for 2016 Method of the Year
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