21/30335555 DC

This standard 21/30335555 DC BS ISO 20917. Determination of available phosphorous and soluble potassium extracted with neutral ammonium citrate and quantified by ICP-OES is classified in these ICS categories:

• 65.080 Fertilizers

This International Standard specifies an ICP-OES method for the determination of the ammonium citrate, disodium-EDTA soluble phosphorus and potassium content in fertilizer extract solutions. This standard is suitable for all inorganic fertilizer products, whether compound or complex fertilizer products or blends thereof and straight concentrated fertilizer products. For organic fertilizers and for liquid fertilizers containing phosphorous acid (H₃PO₃ or phosphite), an alternative method that specifically measures PO₄ is preferred since the ICP-OES measures all elemental phosphorus, which can result in a high bias for these types of fertilizer materials. Due to the inability of the ICP-OES to differentiate between phosphorus species, under normal operating conditions, this method is primarily intended for fertilizer materials in which the source(s) of phosphorus is known. This standard is suitable for reference purposes.