BS/EN 16962-2018 pdf download.Fertilizers – Extraction of water soluble micronutrients in fertilizers and removal of organic compounds from fertilizer extracts.
7 Apparatus
lithe boron content is to be determined it is recommended to minimize contact of all solutions with borosilicate glassware. Use suitable plastic or silica ware especially for extraction step and for removal of organic compounds. Glass volumetric flasks may be used for making up to volume but shall not he used for storage of extracts and solutions.
7.1 Shaker, rotary or horizontal eccentric shaker.
Shaking shall prevent any settling of the sample during extraction.
7.2 Electric hotplate, equipped with variable temperature control.
7.3 Extraction vessels, capacity 500 ml and 1 000 ml.
7.4 Filter paper, ash-free and of recognized and tested quality.
7.5 Beaker, capacity 100 ml.
7.6 Volumetric flasks, capacity 25 ml and 50 ml.
7.7 Watch glass.
8 Procedure
8.1 Preparation of the test solutions
8.1.1 Micro-nutrient content 10 %
For samples with a micro-nutrient content of ≤ 10 % weigh (5 ± 0,005) g of the prepared sample. transfer the sample quantitatively to a 500 ml extraction vessel (73) and add (250 ± 0,2) ml of water (j) at (20 ± 2) O(
8.12 Micro-nutrient content> 10 %
For samples with a micro-nutrient content of> 10% weigh (2 ± 0,002) g of the prepared sample. transfer the sample quantitatively to a 1 000 ml extraction vessel (L3) and add (500 ± 0,5) ml of water (1) at (20±2)°C.
8.2 Extraction
Close the vessel tightly and shake vigorously by hand to disperse the sample. Then place the vessel on the shaker (Li) and shake for 60 mm. The intensity of shaking shall be adjusted to prevent any settling of the sample during the extraction. The temperature of the extraction solution shall be kept at (20 ± 2) °C during the whole extraction time. Filter the extract if necessary immediately after the extraction into a plastic vessel. Use ash-free filter paper of recognized and tested quality (Z4) and discard the first portion of the filtrate (approximately 20 ml). Pipette 20 ml of the extract into a 25 ml volumetric flask, add 2,5 ml of diluted nitric acid solution (2i). fill to the mark with water (1) and mix well. The final concentration of nitric acid is 0,5 mol/l.
Account shall be taken of this dilution when taking aliquot portions and calculating the percentage of micro-nutrient in the sample.
Prepare a blank test solution following the same procedure as for samples.
Acidification of the water extract with nitric acid is not suitable for spectrophotometric determination of molybdenum according to prEN 17043. In this case hydrochloric acid (,4) shall be added; the final concentration of hydrochloric acid is 0,5 mol/l. Acidification with hydrochloric acid shall be used also if precipitation of Fe(Ill) is observed after the addition of nitric acid. If boron is not to be determined standard glassware may be used. If the measurement is not carried out immediately the acidified extracts may be stored in tightly closed plastic vessels for up to 15 days.
If a higher volume of the extract is needed for the measurement to follow, a different volume of the
extract may be pipetted but the final concentration of nitric acid (0.5 mol/l) and the final diluting factor
(5/4) shall be the same. For example, 40 ml of the extract is pipetted into a 50 ml volumetric flask (L6)’
5 ml of diluted nitric acid solution (2J) is added and the flask Is filled to the mark with water (Jj.
Centrifugation of the extracts may be used instead of filtration.
Filter paper with a hydrophobic edge or centrifugation is recommended for finely ground samples.
Some chelated micro-nutrients may undergo photolytic decomposition during the extraction resulting in precipitation. In this case, opaque vessels shall be used for the extraction step and samples shall be stored in the dark
8.3 Removal of organic compounds
Transfer 25 ml of the extract prepared for measurement (see 2) quantitatively into a 100 ml beaker (L5) (use a maximum of 10 ml of water for quantitative transfer from the 25 ml volumetric flask (Lb)). add 5 ml of hydrogen peroxide (). Cover with a watch glass (LZ) and allow oxidation to occur at laboratory temperature for about 1 h, then bring gradually to boiling on an electric hotplate (72) and boil for 0,5 h. If the extract is still visibly coloured by the presence of organic matter, add a further amount of 5 ml of hydrogen peroxide () to the solution once it has cooled. Then boil for 0,5 h to remove the excess hydrogen peroxide. BS/EN 16962-2018 pdf download.