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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 / Page 1 of 5
Authorised by: I Morris / 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

1.12M KCl. Dissolve 149.2  0.1g of KCl in 1 L of water. Store for up to three months at room temperature.

1.2NH4-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.

1.3Boric Acid Solution, approx. 1% m/v. Store for up to four months at room temperature.

1.4Magnesium Oxide Powder (MgO)

1.5Methyl Red Solution. Dissolve 1.0  0.01g of methyl red in 1L of methanol. Store at room temperature for up to two months.

1.6Bromocresol Green Solution. Dissolve 1.0  0.01g of bromocresol green in 1L of methanol. Store at room temperature for up to two months.

1.7Sulphuric Acid, 50 mM volumetric solution, available from VWR. Store for up to six months at room temperature.

Z/004 / Edition: 05 / Page 2 of 5

2.Equipment

2.1Bottles - 250 ml, wide mouth with screw caps.

2.2Kjeldahl Tubes, 250ml and 500ml

2.3Shaking machine - The Griffin bottle shaker (A. Gallenkamp and Co. Ltd., Cat No. SGL - 200) is suitable.

2.4Distillation 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.

2.1The extraction is usually carried out in the sample preparation section and the extract transferred to the Kjeldahl unit as per SOP SAMP/005.

2.1.1Transfer 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.

2.1.2Cap 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.

2.1.3Transfer to the Kjeldahl section.

2.2Carry out a blank determination.

3.Distillation

20ml of the extract from step 2.1.2 is taken for distillation.

3.1Transfer 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.

3.2Add 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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3.3Certain samples will froth excessively on addition of MgO. If this occurs repeat the process using a 500ml Kjeldahl tube.

3.4Transfer the tube to the Kjeltec 2300 analyser and distil the samples following the instructions in the Kjeltec manual, using the pre-set programme, Kjel3

3.5Run blanks between samples to avoid carry over from high samples

4.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

Det / Calculation / Reporting Units
NH4N for extracted solids / Titre x 1.4 x ([100 + wt] – [DM%/100 x wt]) x 1000
V1 x wt / mg/Kg SAR
NH4N for extracted solids to be reported on a dry matter basis / Titre x 1.4 x ([100 + wt] – [DM%/100 x wt]) x 1000 x 100
V1 x wt %DM / mg/Kg DM
NH4N for extracted liquids / Titre x 1.4 x ([100 + V2] – [DM%/100 x V2]) x 1000
V1 x V2 / mg/L SAR

WhereV1 = the volume taken for distillation

V2 = the volume of liquid sample taken for extraction

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5.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.

6.1Chemical hazard data sheet

Chemical / Hazard / Control Measure
Kjeltabs / May be harmful if ingested in quantity
Dust may irritate eyes / Good ventilation
Gloves
Safety glasses
Occupational Exposure Standard – not assigned
Sulphuric Acid / Causes severe burns to eyes and skin
If ingested causes severe internal irritation and damage
Dilute acid irritates the eyes and skin and may cause burns and dermatitis / Fume cupboard
Gloves - nitrile
Safety glasses
Face shield
Occupational Exposure Standard – 1 mg/m3 per 8 hour
Sodium hydroxide solution / Corrosive to body tissue causing burns and severe ulceration
Irritant and harmful as mist or spray
If ingested causes severe internal irritation or damage / Gloves
Safety glasses
Occupational Exposure Standard - 2 mg/m3 NaOH per 8 hour
Ammonium Sulphate / May be harmful if ingested in quantity, causing nausea, vomiting and diarrhoea
May irritate eyes and respiratory system if inhaled as a dust / Respirator
Gloves
Safety glasses
Occupational Exposure Standard - not assigned
Methyl Red / May be harmful if ingested in quantity
Irritating to eyes
Stains / Gloves
Safety glasses
Occupational Exposure Standard - not assigned
Bromocresol Green / May be harmful if ingested in quantity
Irritating to eyes
Stains / Gloves
Safety glasses
Occupational Exposure Standard - not assigned
Z/004 / Edition: 05 / Page 5 of 5

6.1Chemical hazard data sheet (continued)

Chemical / Hazard / Control Measure
Methanol / 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. / Solvent room or fume cupboard
Gloves
Safety glasses
Avoid sources of ignition.
Occupational Exposure Standard - 260 mg/m3 per 8 hour
Boric Acid / May be harmful if ingested in quantity
May be irritating to eyes / Gloves
Safety glasses
Occupational Exposure Standard - not assigned
Chromium Metal Powder / Harmful by ingestion and if inhaled as a dust
May be irritating to eyes, skin and respiratory system
May cause nasal and skin ulceration
Prolonged exposure to dust or fumes may cause vomiting, diarrhoea, liver and kidney damage and stomach pains / Dust mask
Safety glasses
Gloves
Occupational Exposure Standard – 0.5 mg/m3 per 8 hour
Sucrose / Ingestion of significant quantities may lead to metabolic imbalances
May irritate eyes / Safety glasses
Gloves
Occupational Exposure Standard - 10 mg/m3 per 8 hour
Hydrochloric Acid / Causes severe burns to eyes and skin
If ingested causes severe internal irritation and damage
Extremely irritating, harmful vapour / Fume cupboard
Gloves
Safety glasses
Occupational Exposure Standard - 7 mg/m3 per 8 hour