57
Ammonia–1: Phenate Method/ISE
15.2 Borate Buffer
Make this buffer solution up in a 1 L container and then place
directly in the automatic re-pipettor supplied with the starter kit. This
will make 1 L of 0.011 M Na
2
B
4
O
7
. This is enough to treat
1300 samples.
For samples not preserved with acid:
1. Place a 1 L container onto a top-loading balance with a 1000 g
capacity or greater. Tare the balance.
2. Dissolve 2.17 g sodium borate (Na
2
B
4
O
7
) in 964 g deionized
water into the tared 1 L container. Add 36 g 0.1 M sodium
hydroxide (NaOH). Mix well.
3. Transfer this solution to the re-pipettor, screw the cap on tight
and prime the pipet. The solution is ready to use in method
Ammonia–1. Recalibrate the re-pipettor once a month with
deionized water.
For acid preserved samples (2 mL concentrated sulfuric acid
per liter):
1. Place a 1 L container onto a top-loading balance with a 1000 g
capacity or greater. Tare the balance.
2. Dissolve 5 g sodium borate (Na
2
B
4
O
7
) in 964 g deionized water
into a 1 L volumetric flask. Add 22 g sodium hydroxide (NaOH).
Mix well.
3. Transfer this solution to the re-pipettor, screw the cap on tight
and prime the pipet. The solution is ready to use in method
Ammonia-1. Recalibrate the re-pipettor once a month with
deionized water.
15.3 Sources
• APHA–AWWA–WEF Standard Methods for the Examination of
Water and Wastewater, 20th ed. (1998), Method 4500–NH3 D.
to H., pp. 4–106 to 4–112.
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