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Section 16 Ammonia–2: Nesslerization Method
16.1 Micro Dist™ Method
CAUTION
Chemical hazard. Always follow appropriate laboratory safety
procedures when handling chemicals. Always wear personal
protective equipment appropriate for the chemicals you are
handling.
ATTENTION
Danger chimique. Suivez toujours les procédures de
laboratoire de sécurité lors de l'utilisation de produits
chimiques. Veuillez toujours porter l'équipement de protection
personnel approprié pour les produits chimiques que vous
manipulez.
This is a method for distilling samples containing 0.010 to 2.0 mg
N/L with the Micro Dist distillation apparatus.
In the following procedure,
D and M refer to the marks on the ends
of the collector tube.
D means 'distillation' or 'discarded' end and M
means 'measuring' end. See Figure 2 on page 13.
1. Set the controller to 120
°C. Allow the heater block to warm up.
This will take about 40 minutes.
2. With the
M end up, put the required number of collector tubes
into the collector tube rack. Fill the tubes with the trapping
solution and cap the tubes.
3. Place 6.0 mL of sample into each sample tube with an
automatic pipet.
4. Add between 0.5 to 1.0 g of soil or sludge to 5 mL of DI water. If
the sample is high in organics, a smaller sample size or less DI
water may be required. Foaming or caking of the membrane is
often eliminated by the above measures. If not, see Running
Solid Samples with Micro Dist on page 70.
5. To decrease the hydrolysis of cyanates and organic nitrogen
compounds, the sample is buffered at pH 9.5 by adding 0.75
mL of 0.011 M borate buffer (Na
2
B
4
O
7
).
6. Immediately push the
D end of a Ammonia–2 collector tube
over the open end of each sample tube to start the seal.
7. Place the assembly in the press, putting the sample tube
through the hole in the white base. Before pressing the user
should grip the collector tube firmly at the breakaway point to
keep the tube from shifting during the pressing procedure.
8. The pressing motion should be a smooth constant pressure
which is just enough to slide the sample tube inside the
collector tube. A jerky, forced motion may cause added strain to
the tube and could potentially crack it. Press down on the
handle until the stop ring on the sample tube hits the
D end of
the collector tube.
9. Put on the heat-resistant gloves. Push the sample tube and
D
end of each tube all the way into the preheated block so that
the collector tube stop ring touches the block. Placing 21 tubes
should take less than one minute.
10. Set the timer for 30 minutes.
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