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Ammonia–1: Phenate Method/ISE
56
the collector tube stop ring touches the block. Placing 21 tubes
should take less than one minute.
10. Set the timer for 30 minutes.
11. When 30 minutes is up, put on the heat-resistant gloves.
Remove the first tube from the block and immediately pull off its
sample tube using a downward, twisting motion as opposed to
a sideways motion. Remove the sample tube within 4 seconds
of removing it from the block or suck-back of the sample will
occur. Dispose of the sample tube and the hot solution left in it
by dropping it into the sink or waste bucket.
12. Invert each collector tube and place it into the collector tube
rack, now with the
D
minutes to pull and separate all 21 tubes.
13. Parafilm the
end and allow tubes to cool for at least 10
M
minutes.
14. For each collector tube, hold the tube horizontally and rinse its
walls with the distillate in order to homogenize it. Slowly roll the
distillate around in the tube to gather all droplets clinging to the
tube walls into the bulk of the distillate. Then, slowly return the
collector tube to an upright position so that the
Stubborn drops will often fall into the
flicked with a finger.
15. With the
end still up, break the collector tube in half by pulling
D
the
end hard towards the user to break it, then twisting and
D
tearing off the
end. Discard the
D
16. In the remaining
end of the collector tube, dilute to the 6.0 mL
M
mark with deionized water. This results in the original sample
volume, but now in 0.003 M sulfuric acid.
17. Shake the tube with a gentle whipping motion to mix in diluent
water. Do not invert the sample. With the
the tube into the collector tube rack.
18. Determine the solution in the tube with Lachat QuikChem
Method 10–107–06–1–X. or equivalent. There is enough
distillate for two 25 second sample periods. It is best to do this
the same day if possible. Seal both ends with Parafilm if the
sample will not be determined immediately.
19. Typically, the Ammonia–1 collector tubes will contribute an
ammonia blank of 15 mg N/L, or about 1 mM in the 6.0 mL of
distillate. Therefore, it is important to distill both calibration
standards and all samples using the Ammonia–1 tubes.
end up. It should take less than two
end when the tube is
M
end.
D
end down, place
M
end is up.
D
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