|
|
Gas Diffusion Ammonia Method (Water Based Samples)
and Various Extracts |
|
FIAlab standard method for the ammonia
assay in fresh/salt waters and various food
product extracts using the
FIAlab-2500/2600/2700 system.
|
Assay |
Typical Throughput |
Concentration Range |
Notes |
|
Ammonia (Mid to High) |
40 samples/hour |
0.05 to 30 mg (N)/L NH3 |
1 cm flowcell |
|
Ammonia (Low) |
30 samples/hour |
0.005 to 3 mg (N)/L NH3 |
10 cm flowcell |
Principle:
When ammonium in samples are injected into a
basic (pH 12) NAOH carrier/reagent1, NH3
is formed. The NH3 passes across a gas-permeable
membrane into a collector stream (reagent 2)
containing bromothymol blue at pH 6.3.
Collection of NH3 into the bromothymol blue
raises the pH, creating a bluish color change
proportional to the initial ammonium. Peak
wavelength for absorbance is 630 nm.
Recommended reference wavelength is 720 nm.
Consider using a suboptimal wavelength or lower
surface area membrane flowcell for decreased
sensitivity.
Comments:
The FIAlab-2500 is configured so that
the M1 port (output of injected
sample/R1/carrier) tubing passes through
the first mixing coil, through one side
of the membrane cell, and then to waste.
The other side of the membrane cell is
connect to the R2 port. This
flows through the membrane cell, through
the second mixing coil, then through the
absorbance flowcell.
Pump speed should be set to 30.
Sample loop for Mid to High
concentrations should be 6" of 0.03" ID
tubing, and the 1 cm flowcell should be
used..
Sample loop for Low concentrations
should be 12" of 0.03" ID tubing, and
the 10 cm flowcell should be used.
Note on concentration method
sensitivities: the listed
ranges depend on the size/type of
membrane flowcell, and are only
listed as a guidlines. For
higher concentrations it is
recommended that a membrane flowcell
with less surface area be utilized.
Please inquire.
Interferences:
Any component which will interfere with
the ability of NH3 to pass across the
membrane.
|
|
Reagents:
Carrier:
The carrier should be DI water.
Reagent 1:
Sodium hydroxide solution 0.02 M:
Dissolve NaOH in water until a pH of 12 is achieved.
Approximately: 0.8 g NaOH in 1 liter of DI water.
Reagent 2:
Bromothymol
blue solution
Dissolve
0.1 g BTB in 1
liter of distilled water.
Critical: Adjust pH
to 6.3 by drop-wise addition of
of Reagent 1 into Reagent 2.
Stir for 3 minutes and measure pH prior
to each additional drop.
Standards:
100ml ICAMU-100 (ammonia
standard)
Source: 727-524-7732 -
www.exaxol.com
|
|
|
Please email or phone FIAlab Instruments
for additional product information.
Email:
fialab@flowinjection.com,
Voice: 425-376-0450 or 1-800-963-1101,
Fax: 425-376-0451
|
|
|
|