DBP
THM Extraction Procedure
* This procedure is for Extracting THM’s from chlorinated water samples based on USEPA
method 551.1.
Supplies needed
* Based on 1 sample (not duplicated)
Reagents
 8 g NaCl
 3 ml MtBE (methyl tert-butyl ether)
 3 drops of sodium sulfite solution (if stopping the chlorination)
Equipment
 disposable pasteur pipette (if stopping the chlorination)
 disposable pasteur pipette (per sample)
 pipette bulb
 40 ml glass sample vial
 GC vial & cap (per sample)
 GC vial holder tray
 medium weighing tray
 waste beaker
 orbital mixer
 timer
 green pen, black pen
 green tape
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Procedure
Note: THMs are volatile, so be sure to perform procedure quickly and cap samples when not in
use.
A) Sample transfer
1) Mark a 40 ml vial at 30 ml’s and fill to the mark. It is recommended that you keep a
permanent stock of marked 40 ml vials.
B) Sample prep
2) Stop the chlorination process if needed by the addition of 65 mg  ~3 mg Ammonium
Chloride
3) Add 8 g  ~0.1 g of NaCl (decreases solubility of ether in water & increases partitioning).
Pre-weighing this for each sample prior to sample prep is recommended.
4) Add 3 ml of MtBE (via bottle top pipetter)
5) Recap vials, shake for 2 minutes on an orbital mixer (until most of salts are dissolved)
6) Let stand for ~15 minutes (for separation).
C) Extraction
7) Remove ~ 2 ml of the top organic layer with a pasteur pipette and add to 2 ml volumetric
flask.
Organic Layer
8) Transfer sample to GC vial and cap. Analyze as soon as possible. Keep sample in freezer.
9) Make one blank with only MtBE
Fill with 30 ml
sample
sodium
sulfite
(if needed)
8 g NaCl
~2 ml organic
layer
3 ml MtBE
1)
2)
3)
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~2 ml organic
layer to GC vial
Cap vial
Shake 2 min.
Stand 15 min.
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D) Clean-up
All residual MtBE and samples should be left in the hood to evaporate. White salt crystals will
be left in the waste containers following evaporation; these should be cleaned out after all MtBE
has evaporated.
QA/QC:
THM analysis can have a high variability in results due to the many steps and variables in the
process. It is recommended that triplicate analyses be performed on 10% of the samples to
quantify the variability in results.
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