Determination of Anions by Ion Chromatography 1 SCOPE AND FIELD OF APPLICATION This method is suitable for the determination of inorganic anions in Ammonia Solution in the range 100 ppb to 50 ppm m/v. 2 PRINCIPLE The sample is passed through a column of anion exchange resin, on which the anions are absorbed and separated. They are then eluted with dilute sodium carbonate/sodium hydrogen carbonate solution and passed through a suppressor. This replaces the cations with hydrogen ions and thus reduces the background conductivity of the eluent. Final measurement is by conductivity

1. GBH Enterprises, Ltd.
Plant Analytical Techniques
ANHYDROUS AMMONIA: DETERMINATION OF ANIONS BY ION
CHROMATOGRAPHY
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2. AMMONIA SOLUTION: Determination of Anions (Cl, PO,, NO, b SO,) by Ion
Chromatography
WARNING AND SAFETY PRECAUTIONS:
AMMONIS SOLUTION: SPLASHES INT0 EYES CAN CAUSE SEVERE
BURNS. AVOID INGESTION. PRESSURE MAY BUILD UP IN CLOSED
CONTAINERS.
1
SCOPE AND FIELD OF APPLICATION
This method is suitable for the determination of inorganic anions in
Ammonia Solution in the range 100 ppb to 50 ppm m/v.
2
PRINCIPLE
The sample is passed through a column of anion exchange resin, on
which the anions are absorbed and separated. They are then eluted with
dilute sodium carbonate/sodium hydrogen carbonate solution and passed
through a suppressor. This replaces the cations with hydrogen ions and
thus reduces the background conductivity of the eluent. Final
measurement is by conductivity.
3
Reagents
During the analysis use only reagents of analytical reagent grade, unless
otherwise specified, and water which has been deionized and then
distilled from an all glass apparatus, or water of equivalent purity.
3.1
Standard stock anion solution, weigh respectively 0.4125 g sodium
Chloride, 0.7164 g potassium dihydrogen phosphate, 0.6853 g sodium
nitrate and 0.9075 g potassium sulfate and transfer to a 500 ml one mark
volumetric flask add approximately 300 ml water. Shake until dissolution is
complete, dilute to the mark with water and mix. 1 ml of this solution
contains 0.5 mg Cl, 1.0 mg PO, 1.0 mg NO, and 1.0 mg SO,.
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3. 3.2
Preparation of calibration solution, pipette 10 ml of standard stock
anion solution (3.1), using a Grade A 10 ml pipette, into a 1 liter one mark
volumetric flask and dilute to the mark with water and mix. 1 ml of this
solution contains 5 µg Cl, 10 µg PO,, 10 µg NO, and 10 µg SO,.
3.3
Eluent (0.0017 M NaHC03, 0.0018 M Na2CO3), weigh 0.713 + 0.001 g of
sodium hydrogen carbonate and 0.955 + 0.001 g of anhydrous sodium
carbonate, dissolve in water and transfer to a 5 L volumetric flask (4.1)
and dilute to volume with water.
SODIUM CARBONATE - IRRITATING TO EYES - DUST IS
STERNUTATORY – SODIUM HYDROGEN CARBONATE MAY
IRRITATE EYES AND RESPIRATORY SYSTEM IF INHALED AS DUST
3.4
Suppressor regenerant (0.025 M, H2SO4), transfer 3.5 mL of concentrated
Sulfuric acid (S.G. = 1.84) into a 5 L volumetric flask containing water and
dilute to volume with water.
SULFURIC ACID CAUSES SEVERE BURNS TO EYES AND SKIN
4
APPARATUS
4.1
Standard volumetric glassware, class A.
4.2
Ion chromatograph system.
A suitable system is a Dionex QIC model comprising a micromembrane
suppressor, an AG4A guard column and AS4A sample column, a 5 µg
sample loop; computing integrator, a Shimadzu C-R3A model is suitable;
a 3 Slot expansion accessory, a Shimadzu C-R3A model is suitable;
Automation interface supplied by Dionex; a flat-bed recorder, capable of 0
- 10 mV; Compressed air supply, at 5 p.s.i. (Figure 1 shows a schematic
diagram).
4.3
Auto-sampler system, a suitable system is supplied by Dionex consisting
of an autosampler with autosample vial racks.
4.4
Autosampler vials, 5 mL autosampler vials with filter caps supplied by
Dionex are suitable.
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4. 4.5
Platinum evaporating dish.
4.6
Steam bath.
5
Sample Pretreatment
5.1
Transfer a volume equivalent to 100 g of the sample into the platinum
evaporating dish (4.5) and reduce the volume to approximately 5 ml on a
steam bath (4.6) to remove all the ammonia. Transfer the residue to a 100
ml one mark volumetric flask, wash the platinum dish with 4 x 10 ml
portions of water, adding the washings to the residue in the volumetric
flask. Dilute to the mark with water and mix.
6
Procedure
6.1
Ensure that the Ion chromatagraph system (4.2), autosampler system
(4.3), eluent (3.3) and suppressor regenerant (3.4) are connected in
accordance with the manufacturer's instructions.
6.2
Select the method for anionic determination. The parameters are set out in
Annex 1.
6.3
Fill sample vials (4.4) with anion standard (3.2) and place in the
autosample vial rack on the autosampler (4.3).
6.4
Test sample, fill a sample vial (4.4) with sample and place in the
autosample vial rack on the autosampler (4.3).
6.5
Repeat procedure (6.4) for the required number of test samples,
6.6
Start the run in accordance with the manufacturers instructions. The
results will be recorded by the computing integrator. Figure 2 shows a
typical chromatogram.
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5. 7
Expression of Results
7.1 The results are expressed as Cl, NO, PO, and SO, ppm m/v.
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Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
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6. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown
Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass
Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance
Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts /
Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries
Web Site: www.GBHEnterprises.com