This document describes analytical methods used in a fertilizer laboratory to determine the contents of various elements in fertilizers. The laboratory uses Inductively Coupled Plasma and Atomic Absorption Spectrophotometry to determine elements like potassium, magnesium, and phosphorus. Specific procedures are outlined for determining magnesium and phosphorus content, which involve preparing standard solutions, digesting samples, and measuring absorbances of sample solutions and standards to calculate concentrations. The roles of potassium, magnesium, and phosphorus in plant growth are also briefly discussed.

1. FERTILIZER
LABORATORY

2. FERTILIZER
Aim : to determine the contain of element e.g. K, Mg, P,
Ca in the fertilizer followed by the specification.
Instrument used:
Inductively Coupled Plasma(ICP)- determine all
element at one time include heavy metal if necessary.
Atomic Absorption Spectrophotometer(AAS) & UV
Spectrophotometer - one element at a time.

3. Determination
of pH value
Determination
of moisture
content
Determination
of potassium
Determination
of magnesium
Determination
of phosphorus
Trace element
FERTILIZE
R
ANALYSIS

4. DETERMINATION OF POTASSIUM AND MAGNESIUM
Why we need potassium and magnesium?
POTASSIUM - provide the ionic environment for metabolic
process in cytosol.(growth regulation)
- potassium ions (K+) for protein synthesis and
opening and closing of stomata.
MAGNESIUM - part of chlorophyll in plant for photosynthesis

5. METHOD
• Method for the determination of magnesium
Determination of water-soluble magnesium content (MgO)
• Principle
Magnesium in magnesium sulphate fertilizers is extracted in
boiling water and the magnesium content determined by
atomic absorption spectrophotometer.
• Reference: MS 417: Part 6: 1994

6. PROCEDURE
•Sample preparation
-registration
-drying
-grinding
•Weigh the sample
•Add distilled water and HCl

7. • Digest the solution using hot plate at boiling
point around 20minutes
• Leave to cool
• Transfer into volumetric flask and dilute to
the mark (250ml)
• Mixed the solution and filter in plastic vial
• Further dilution(100ml)
• Add strontium nitrate(5ml) and dilute to the
mark
• To remove phosphate from magnesium and
calcium and prevent interference from other
elements

8. • Preparation for Atomic Absorption
Spectrophotometer
• Standard stock solution
- Potassium dihydrogen sulphate solution
- Magnesium sulphate solution
• For 1000ppm,weigh 4.3928g.
• Dry in oven for 2 hours
• Undergo further dilution(m1v1=m2v2)
• 0, 0.25, 0.5, 0.75, 1.00 and 1.25 ppm

9. • Pre-calibrate the AAS with standard stock
solution
• Run the AAS
• Then, we can determine the concentration of
the solution

10. DETERMINATION OF PHOSPHORUS
Why phosphorus important to plant?
• Essential to stimulate early plant growth and hastens the
maturity.
• Development of root health.
• Classified as macronutrient.

11. Methodology:
• molybdovanadate method (yellow method).
Reference:
•MS 417: Part 4: 1994
Apparatus:
Spectrophotometer.
Principle:
•Amount of light transmitted (yellow colour) dependent on the
concentration of phosphorus.
•Spectophotometric absorption curve from known standard
phosphorus solutions determined in unknown solution.

12. Standard stock solution:
 Potassium dihydrogen phosphate (4.3928g in 1L)
 1000ppm 100ppm 0ppm 2ppm 4ppm 8ppm 10ppm
Reagent used:
 Molybdovanadate reagent: Ammonium molybdate (100ml) mixed together
with ammonium
vanadate (150ml).
Aqua regia:
 Mixing the HCl & HNO3 together.

13. Procedure
• Sample preparation and
weigh the samples (fertilizer)
• Add distilled water.
• Add 10ml HCl and 5ml HNO3 and boil.
• transfer into volumetric flask.
• Mark-up with distilled water then filter.

14. • 1ml of sample solution is pipette into 100ml volumetric flask.
• Add Molybdovanadate reagent and diluted to the mark with
distilled water.
• Prepare calibration standard (0,2,4,6 & 8 ppm) from the stock
solution (1000ppm) and take reading after 30 minutes.

15.  Determine phosphate at acidic colour at pH ±
2.6
 Double acid method is used.
 We put HCl and HNO3 to convert all
polyphosphate (P2O7) to orthophosphate
(PO4
3-).
 phosphate + metavanadate =
phosphomolybdate acid + water. (yellow
colour)