DBP
Diazomethane Preparation Procedure
* This procedure is for preparing the diazomethane for DBP analysis
Supplies needed
* Based on use of the small reactor
Reagents
 ~1 g MNNG (1-Methyl-3-nitro-1-nitrosoguanidine, 97%, Aldrich)
 MQ water
 6 ml MtBE (Methyl-tert Butyl Ether)
 1 ml ~5N NaOH
Equipment
 Reaction chamber (large)
 500 ml erlenmeyer flask (to hold reaction chamber)
 800-1000 ml plastic beaker
 ~3 L crushed ice
 1 ml plastic syringe
 25 gauge, 5/8” luer lock needle
 ~25 ml erlenmeyer flask or beaker
 Teflon tape
 Small glass funnel
Precautions!!!
* MNNG and the gas produced are very dangerous. Always perform in hood with proper
personal protection equipment and training.
Apparatus
Cap w/septa
O-ring

Holding Flask
Reactor base
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Reactor stem
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Procedure
1) Tilt reactor so hole in reactor stem is facing up. It is important to make sure all additions to
the reactor stem do not go through the hole.
2) Add the MNNG to the base of the reactor stem up to the fill line (~1 g)
Reactor Stem
Fill line
MNNG
3) Add ~1 ml MQ water to reactor stem to moisten the MNNG and firmly screw on cap w/
septa.
4) Add 6 ml MtBE to reactor base
5) Place reactor stem in the reactor base with O-ring sandwiched in between glass flange. Wrap
Teflon tape around the reactor at the O-ring and clamp tightly. Wrap Teflon tape around the
cap.
6) Prepare and ice bath in a 800 ml plastic beaker. Place reactor in ice bath and allow reactor to
reach thermal equilibrium. Adding some water to the ice will increase the heat transfer.
7) Plunge ~25 gauge needle through septa in reactor stem. Add ~1 ml of NaOH very slowly in
a drop wise fashion (until all MNNG is gone). [Reaction is Extremely Exothermic!]. Be
sure to keep pressure on the syringe since significant pressure builds up inside reactor. Be
sure to maintain good heat transfer to the ice bath.
8) Allow ~30 minutes for reaction completion while in the ice bath. The outside MtBE solution
should turn a moderate or deep yellow. If this does not occur, the solution is no good.
9) Allow the pressure to slowly release by loosening the cap first. Transfer diazomethane to 25
ml erlenmeyer flask via small glass funnel. Keep the diazomethane cold and use as soon as
possible after preparation. If bubbles form following addition of the diazomethane to the
sample, then diazomethane solution is good.
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