Determination of Moisture in Fertilisers and Analytical Quality Assurance in Fertiliser Production

Keywords: Fertiliser moisture, Water determination, Fertiliser caking, Fertiliser analysis, Quality assurance.

1. DETERMINATION OF MOISTURE IN FERTILISERS.

Summary.

The moisture content of fertilisers is a very important production parameter, owing to the correlation between moisture and physical properties. The choice of water determination method in this connection is not obvious. It has been argued that a method for ‘free water’ should be most appropriate.

After a short discussion regarding different ways to classify the state of water and the principles of some commonly used methods, a revised method for the determination of ‘free water’ is presented in this paper.

The revised method is in principle similar to the official AOAC extraction method. Some changes in the analytical procedure are proposed, particularly the change from 1,4-dioxane to isopropanol as an extraction agent.

The accuracy of the new method is discussed and evaluated.

The importance of a proper pre-treatment of the sample is stressed. Large moisture changes may occur during sample grinding.

Finally some practical experiences regarding the correlation between water content and the physical properties of fertilisers are discussed.

I Dellien and C Svensson, Supra Aktiebolag, Landskrona, Sweden.

21 pages, 10 figures, 3 tables, 12 refs.

2. ANALYTICAL QUALITY ASSURANCE IN FERTILISER PRODUCTION.

Summary.

The production of fertilisers is a chemical process which requires a careful chemical characterisation of the raw materials, intermediate compounds and the final products. The analytical methods used for the quality control of production must fulfil stringent requirements with respect to accuracy and precision.

This paper describes a programme to evaluate the quality of the analytical results and the analytical standard that can be achieved in routine analytical work. This is usually termed a quality assurance programme. Examples of method improvements are discussed, as well as aspects of the management of the programme.

I Dellien and C Svensson, Supra Aktiebolag, Landskrona, Sweden.

14 pages, 2 figures, 6 tables, 3 refs.