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STANDARD OPERATING PROCEDURE
Z/004
The determination of ammonium in organic wastes (liquid or solid)
Edition: 05
Last amended 31.01.2006
Authorised by: I Morris
Page 1 of 5
Date:
INTRODUCTION
NH4-N is extracted from organic waste samples with 2M KCl.
Samples appearing to have less than 10% solids are routinely treated as liquids, samples
appearing to have above 10% solids are routinely treated as solids. An aliquot of the
extract is made alkaline and the released ammonia is determined titrimetrically, after
removal by distillation.
REFERENCE DOCUMENTS
RB427 The Analysis of Agricultural Materials1985. Method 53.
SOP H/007 – Determination of residual moisture in plant material and animal
feedingstuffs
SOP Z/002 – Determination of nitrogen/crude protein content using the Kjeldahl technique
SOP SAMP/006 – Procedures for handling potentially biohazardous materials
MATERIALS AND EQUIPMENT
1.
Reagents
1.1
2M KCl. Dissolve 149.2  0.1g of KCl in 1 L of water. Store for up to three
months at room temperature.
1.2
NH4-N Standard Solution, 1.4 mg/ml. Dry ammonium sulphate at 102 
2°C for one hour  5 min and cool to room temperature in a desiccator.
Dissolve 3.3035  0.001g of the dried salt in deionised water and dilute to
500ml with deionised water. Store for up to three months at room
temperature.
1.3
Boric Acid Solution, approx. 1% m/v. Store for up to four months at room
temperature.
1.4
Magnesium Oxide Powder (MgO)
1.5
Methyl Red Solution. Dissolve 1.0  0.01g of methyl red in 1L of methanol.
Store at room temperature for up to two months.
1.6
Bromocresol Green Solution. Dissolve 1.0  0.01g of bromocresol green
in 1L of methanol. Store at room temperature for up to two months.
1.7
Sulphuric Acid, 50 mM volumetric solution, available from VWR. Store
for up to six months at room temperature.
Z/004
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Equipment
2.1
Bottles - 250 ml, wide mouth with screw caps.
2.2
Kjeldahl Tubes, 250ml and 500ml
2.3
Shaking machine - The Griffin bottle shaker (A. Gallenkamp and Co. Ltd.,
Cat No. SGL - 200) is suitable.
2.4
Distillation units, Kjeltec 2300 Auto analyser for direct steam distillation.
PROCEDURES
1.
Sampling
Non-food, non-soil samples are prepared according to SOP SAMP/015
2.
Sample Extraction
Samples are extracted with 2M KCL prior to distillation. Some samples can be
distilled directly.
2.1
The extraction is usually carried out in the sample preparation section and
the extract transferred to the Kjeldahl unit as per SOP SAMP/005.
2.1.1 Transfer 20  0.1g of fresh solid waste or 20  0.1ml of an organic
liquid waste into a bottle. Add 100  2ml of 2M KCl. If the sample size
is small then it is acceptable to weigh out 10g and use 50ml of
extractant.
2.1.2 Cap the bottle and place on the shaking machine. Shake for two hours 
10 min. Filter through a 15 cm Whatman No. 541 filter paper and retain
the filtrate for the determination of ammonium - nitrogen.
2.1.3 Transfer to the Kjeldahl section.
2.2
3.
Carry out a blank determination.
Distillation
20ml of the extract from step 2.1.2 is taken for distillation.
3.1
Transfer the required volume of extract to a 250ml Kjeldahl tube. in Table 1
below. Volumes are taken to ±0.01ml and the volume is recorded.
3.2
Add approximately 0.5g of MgO and wash this down the neck of the tube
with deionised water. The total volume of the tube should be between 20ml
and 150ml.
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3.3
Certain samples will froth excessively on addition of MgO. If this occurs
repeat the process using a 500ml Kjeldahl tube.
3.4
Transfer the tube to the Kjeltec 2300 analyser and distil the samples
following the instructions in the Kjeltec manual, using the pre-set
programme, Kjel3
3.5
Run blanks between samples to avoid carry over from high samples
5
Calculation of result
Standard Solution (1.2) = 1.4 mg/ml NH4N
5ml of Standard Solution gives a titre of 5ml
So, 1ml of titre ≡ 1.4mg NH4N
concentrat ion of NH4 N in the tube  titre 1.4
Det
Calculation
NH4N for
extracted solids
Titre x 1.4 x ([100 + wt] – [DM%/100 x wt]) x 1000
V1 x wt
Reporting
Units
mg/Kg SAR
NH4N for
Titre x 1.4 x ([100 + wt] – [DM%/100 x wt]) x 1000 x 100 mg/Kg DM
extracted solids to
V1 x wt
%DM
be reported on a
dry matter basis
NH4N for
mg/L SAR
Titre x 1.4 x ([100 + V2] – [DM%/100 x V2]) x 1000
extracted liquids
V1 x V2
Where
V1 = the volume taken for distillation
V2 = the volume of liquid sample taken for extraction
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AQC
An AQC duplicate is analysed on a basis of 1 per 10 samples. If the batch is
smaller than the AQC frequency should be one per batch.
6.
Safety
The Kjeldahl methods and procedures are potentially very hazardous and are carried
out in a corrosive environment. Neoprene gloves and gauntlets are provided together
with facial visors. Gloves should be worn at all times because of possible
dermatological effects of tablets and even dilute acids and alkalis. Disposable gloves
are used for sample handling and weighing out. Additional safety extraction fans have
been fitted in the digestion room in case of failure of the main extraction fan. The main
fan needs to be switched on before samples have acid added. To avoid noxious fumes
from cold acid, ensure the room is well ventilated. Clothing, especially jeans can
become spotted with holes from splashes of dilute acid. In case of accidental acid
drenching, an emergency shower is provided in the digestion room. This shower should
be tested every week to ensure it continues to be in good working order.
6.1
Chemical hazard data sheet
Chemical
Kjeltabs
Hazard
May be harmful if ingested in quantity
Dust may irritate eyes
Control Measure
Good ventilation
Gloves
Safety glasses
Occupational Exposure Standard – not assigned
Causes severe burns to eyes and skin
Fume cupboard
Sulphuric
If ingested causes severe internal irritation and
Gloves - nitrile
Acid
damage
Safety glasses
Dilute acid irritates the eyes and skin and may cause Face shield
burns and dermatitis
Occupational Exposure Standard – 1 mg/m3 per 8 hour
Corrosive to body tissue causing burns and severe
Gloves
Sodium
ulceration
Safety glasses
hydroxide
Irritant
and
harmful
as
mist
or
spray
solution
If ingested causes severe internal irritation or
damage
Occupational Exposure Standard - 2 mg/m3 NaOH per 8 hour
May be harmful if ingested in quantity, causing
Respirator
Ammonium
nausea, vomiting and diarrhoea
Gloves
Sulphate
May irritate eyes and respiratory system if inhaled as Safety glasses
a dust
Occupational Exposure Standard - not assigned
May be harmful if ingested in quantity
Gloves
Methyl Red
Irritating to eyes
Safety glasses
Stains
Occupational Exposure Standard - not assigned
Gloves
Bromocresol May be harmful if ingested in quantity
Irritating
to
eyes
Safety glasses
Green
Stains
Occupational Exposure Standard - not assigned
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Chemical hazard data sheet (continued)
Chemical
Methanol
Hazard
Control Measure
Solvent room or
fume cupboard
Gloves
Safety glasses
Avoid sources of
ignition.
Highly flammable
Vapour/air mixture explosive
Toxic by ingestion
Damaging if splashed in eyes
High concentrations of vapour may cause
dizziness, stupor, cramps and digestive
disturbance. Lower levels may cause headache
and nausea. Chronic effects - damages the central
nervous system, particularly the optic nerve and
internal organs.
Can react vigorously with oxidising materials
Can react vigorously with chloroform in the
presence of sodium and sodium hydroxide
Avoid contact with oxidisers.
Occupational Exposure Standard - 260 mg/m3 per 8 hour
Boric Acid
May be harmful if ingested in quantity
Gloves
May be irritating to eyes
Safety glasses
Occupational Exposure Standard - not assigned
Chromium
Harmful by ingestion and if inhaled as a dust
Dust mask
Metal Powder May be irritating to eyes, skin and respiratory
Safety glasses
system
Gloves
May cause nasal and skin ulceration
Prolonged exposure to dust or fumes may cause
vomiting, diarrhoea, liver and kidney damage and
stomach pains
Occupational Exposure Standard – 0.5 mg/m3 per 8 hour
Sucrose
Ingestion of significant quantities may lead to
Safety glasses
metabolic imbalances
Gloves
May irritate eyes
Occupational Exposure Standard - 10 mg/m3 per 8 hour
Hydrochloric Causes severe burns to eyes and skin
Fume cupboard
Acid
If ingested causes severe internal irritation and
Gloves
damage
Safety glasses
Extremely irritating, harmful vapour
Occupational Exposure Standard - 7 mg/m3 per 8 hour