BS ISO 20702:2017 pdf download

BS ISO 20702:2017 pdf download.Fertilizers and soil conditioners — Determination of microamounts of inorganic anions in fertilizers by ion chromatography
1 Scope
This document specifies the ion chromatography method for the determination of microamounts of water soluble inorganic anions, such as fluoride (F − ), chloride (Cl − ), bromide (Br − ), iodide (I − ), nitrite (NO 2 − ) and thiocyanate (SCN − ), in fertilizers.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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.
ISO 8157, Fertilizers and soil conditioners — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8157 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
Water soluble inorganic anions are extracted by sonication, centrifugation and purification using a C18 column and a Ba-ion column (where applicable). During pre-treatment, the anions are filtered by a 0,22 μm aqueous filter. They are determined by ion chromatography. Anions are separated based on their affinity for the exchange sites on the analytical column. The suppressor device reduces the background conductivity of the eluent to a low level by replacing the cations with the hydrogen ions, thereby converting the anions in the fertilizer sample to their corresponding acids with higher conductivity. The separated anions (in their acid forms) are measured by an electrical-conductivity detector. Anions are identified based on their retention times compared to known standards. Quantitation is accomplished by measuring the peak height or area compared to a calibration curve generated from known standards.
5 Reagents
WARNING — Acetone and methanol are flammable and toxic. Refer to the applicable safety data sheet (SDS). The related operations shall be performed in the fume hood. This document does not point out all possible safety problems; therefore, the user shall bear the responsibility to take proper safety and health measures. Analytical grade reagent (A.R.) chemicals shall be used in all tests, unless otherwise indicated. The purity of water used throughout shall be understood to mean reagent water with electrical resistivity ≥18,2 MΩ·cm. In the list below, G.R. refers to guarantee reagent.
5.7 Potassium hydroxide eluent. Dissolve 5,611 g potassium hydroxide (0,1 mol, 5.2) in water (5.1). Dilute this solution to 1 l with water (5.1) and mix thoroughly. The potassium hydroxide solution can also be prepared by automated eluent generation system (OH- type). The potassium hydroxide eluent is used for gradient chromatography conditions.