BS ISO 19822-2018 pdf free download.Fertilizers and soil conditioners — Determination of humic and hydrophobic fulvic acids concentrations in fertilizer materials
4 Principles
4.1 This method determines ash-free quantities of HA and HFA gravimetrically after separation from their matrix.
4.2 The method of extracting HA and HFA utilizes a strong base to extract the alkaline-soluble materials, and then, after removal of non-soluble components, the alkaline solution is acidified to flocculate the HA.
4.3 The liquid supernatant remaining after the removal of the HA is called the Fulvic Fraction. The Fulvic Fraction, which can contain Hydrophobic Fulvic Acids (HFA), is treated to determine the quantity of HFA in the Fulvic Fraction by selective adsorption onto a methacrylic-ester resin designed to separate the HFA from non-humic compounds. The material retained by the hydrophobic resin is referred to in the literature as the hydrophobic acid fraction of soluble organic matter [3] .
5 Warnings
5.1 Requirements
5.1.1 Good laboratory practices
Related standards (e.g. ISO/IEC 17025) should be followed at all times in regards to personal protective equipment (safety glasses, handling strong acids, hydrochloric acid) and alkali (sodium hydroxide).
5.1.2 Moisture control
Humic and fulvic acids are hygroscopic materials; it is critical to prevent absorption of moisture during the handling of dried materials.
5.3 Lignosulfonates
Lignosulfonates will damage the hydrophobic resin. This analytical method cannot differentiate between hydrophobic fulvic acids and lignosulfonates, therefore pre-screening for the presence of lignosulfonates is recommended for liquid products of unknown origin.
See Annex A.
5.4 Temperature control
Do not exceed 65 °C when drying the humic and fulvic analytes. The analytes are subject to decomposition at higher temperatures.
6 Reagents
6.1 Sodium hydroxide solution, 0,1 M, dilute 3,99 g of 99,99 % purity NaOH in 1 l of deionized water.
6.2 Sodium hydroxide solution, 0,5 M, dilute 19,99 g of 99,99 % purity NaOH in 1 l of deionized water.
6.3 Hydrochloric acid solution, 6 M, dilute 12 M HCl with an equal part of deionized water.
6.4 Hydrochloric acid solution, 1 M, dilute 83,3 ml of 12 M HCl with 1 l of deionized water.
6.5 Hydrochloric acid solution, 0,1 M, perform a 1:10 dilution using 1 M HCl prepared in 6.4 with final volume of 1 l using deionized water.
6.6 Nitrogen gas (UN1066) 99,9 % purity.
6.7 Methacrylic-ester resin, 40–60 mesh, approximately 0,79 ml·g −1 pore volume, 225 Å mean pore
size, 160 m 2 ·g −1 surface area, for adsorption of materials up to 150 000 MW, e.g. Supelite DAX-8 Resin, or
any other available resin meeting equivalent properties.
6.8 Amberlite IR-120 strong cation exchange resin, hydrogen form.
6.9 Deionized water [8] .
6.10 Acetone.
7 Apparatus
7.1 Analytical balance with draft guard: capacity 210 g, with readability to ±0,000 1 g.
7.2 Drying oven, capable of 120 °C, precision ±3 °C.
7.3 Centrifuge, minimum relative centrifugal force 1 500 × g, capable of 3 900 × g.
7.4 4 ml to 50 ml or 250 ml polyethylene or HDPE centrifuge tubes, or heavy duty high temperature resistant centrifuge tubes capable of 600 °C (for example; Kimble-Chase, catalog number 45212-50 KIMAX).
7.5 4 ml to 100 ml wide-form crucibles (for example: Fisher Scientific catalog number FB-965-M).
7.6 Rotary evaporator 400 ml capacity.
7.7 Magnetic stir plates and 5 cm to 7 cm long magnetic stir bars.
7.8 pH meter and electrode.
7.9 Electrical conductivity meter with probe having a calibrated cell constant of approximately one, as determined using standard protocols.
7.10 Spectrophotometer, capable of measuring ±0,005 absorbance units at 350 nm.
7.11 Peristaltic pump with a minimum flow rate of 1,2 ml·min −1 and tubing.
7.12 Muffle furnace.
7.13 Rotating shaking mixer.
7.14 Desiccator with silica gel (or its equivalent) as desiccant.
7.15 Erlenmeyer flask, 1 000 ml.
7.16 Beaker, 4 l.
7.17 Graduated cylinder, 1 000 ml.
7.18 Glass chromatography column, 4 cm × 25 cm for DAX-8 resin.
7.19 Glass chromatography column, 5 cm × 60 cm for IR120 H+ exchange resin.
7.20 Ceramic mortar and pestle.
7.21 Sieve, 74 µm (#200 US mesh).
7.22 Parafilm® 1) .
8 Preparing crucibles, drying, and weighing samples
8.1 Preparing crucibles
8.1.1 If using new crucibles, first wash them with acetone and then dry them in an oven at 105 °C for 2 hours.
8.1.2 Prepare previously used crucibles by washing in acetone, then firing them in a muffle furnace at 500 °C for 2 hours. Cool the crucibles in a desiccator to room temperature. Remove from desiccator when cool, record weight of the crucibles to four decimal places.
8.2 Drying and weighing solid analytical samples
8.2.1 If the analytical sample is a solid material, crush and screen approximately 5 g of the analytical sample to ≤75 µm making sure that the powder becomes well homogenized.
8.2.2 Transfer approximately 5 g analytical sample to a 100 ml crucible prepared according to 8.1.
8.2.3 Place the analytical sample in a drying oven for 24 h at a temperature of 62 ± 3 °C. (do not exceed 65 °C). If any clumping of the sample occurs during drying, break up the clumps with a glass rod. Continue drying until the sample is dried to a constant weight. This can take up to 24 h;
8.2.4 After achieving constant weight, remove the analytical sample from the drying oven and immediately place in a desiccator to cool.
NOTE Both humic and fulvic acids are hygroscopic materials, it is critical to prevent absorption of moisture during the handling of these materials.
8.2.5 Weigh out approximately 2,5 g test portion from the dried analytical sample in a pre-weighed crucible prepared according to 8.1, taking precautions to prevent moisture adsorption while handling.
Record the test portion + crucible weight to four decimal places. Proceed to 9.1 immediately or return the crucible with test portion to the desiccator.
8.2.6 Determine the weight of the test portion by subtracting the weight of the crucible from the test portion + crucible; record the result as the Test Portion Dried Weight.BS ISO 19822 pdf download