EN 15962:2011 – Fertilizers – Determination of the complexed micro-nutrient content and of the complexed fraction of micro-nutrients

1 Scope
This European Standard specifies a general method for the determination of the micronutrients complexed by complexing agents in fertilizers. The method allows the determination of the total concentration of each complexed micronutrient in complexes after subtraction of the chelated micro-nutrients content, but it does not identify the individual complexing agents. This procedure concerns EC-fertilizers which contain complexed micro-nutrients covered by Regulation (EC) No 2003/2003. The method is applicable to a mass fraction of the metal complexed of at least 0,07 %, 0,006 % and 0,035 % of Fe, Mn and Zn respectively (see [2]). A lower limit of quantification has not been established for Cu and Co.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1482-2, Fertilizers and liming materials — Sampling and sample preparation — Part 2: Sample preparation EN ISO 3696:1995, Water for analytical laboratory use — Specification and test methods (ISO 3696:1987)
3 Principle
The method is based on the precipitation of the inorganic forms at pH 9. Then the complexed forms of an element remain in solution and are separated from the non complexed forms. The complexed forms are collected and their content determined by spectrometry, as well as the soluble element content. NOTE For additional information see [2] and [3].
4 Interferences
Any substance combining with a micro-nutrient to form a stable soluble compound (chelate or complex) at pH 9, will prevent the precipitation of the metal, and account for a certain degree of complexation. This is the case for chelating agents. If the presence of chelates is suspected the appropriate analytical method should be used (see Bibliography) to identify and quantify the amount of element chelated, that should be subtracted from the amount of the element given by this method in order to obtain the actual amount of element complexed.
5 Apparatus
All glassware, filters, and equipment parts coming in contact with samples and solutions, should be appropriate for micro-nutrient analysis, be very clean and free from contamination, especially by the elements Co, Cu, Fe, Mn, and Zn.
Usual laboratory equipment, glassware and in particular the following:
5.1 Magnetic stirrer.
5.2 Balance, capable for weighing to an accuracy of 1 mg.
5.3 pH-meter, equipped with a glass electrode; the system shall be calibrated with pH 7 and pH 10 calibration buffers.
5.4 Membrane filters, micro-membrane filters resistant to aqueous solutions, with porosity of 0,45 µm.
EN 15962:2011 – Fertilizers – Determination of the complexed micro-nutrient content and of the complexed fraction of micro-nutrients