Determination of P2O5 content in feed phosphates
Principle: the P2O5 content is determined by measuring the intensity of the yellow coloured complex formed with ammonium molybdovanadate reagent in nitric acid solution Procedure.
P2O5 total
Boil an exact quantity of the sample with HNO3 and water. Cool and dilute with water. After filtration measure the intensity of the yellow coloured complex formed with the molybdovanadate reagent in nitric acid solution. Based on a calibration line of standard solutions the content of the total P2O5 can be calculated.
P2O5 soluble in ammoniumcitrate Petermann
Transfer an exact quantity of the sample in an ammonia citrate solution according to Petermann. After mixing at 45 °C dilute with water. After filtration measure the intensity of the yellow coloured complex formed with the molybdovanadate reagent in nitric acid solution. Based on a calibration line of standard solutions the content of the P2O5 soluble in ammoniumcitrate Petermann can be calculated.This value gives only an indication of the quality of the phosphates if it exceeds 95% solubility in both 2 % citric acid and ammoniumcitrate Petermann, it can be considered of good quality. However, it does not predict digestibility.
P2O5 soluble in 2 % citric acid
Transfer an exact quantity of the sample in a 2 % citric acid solution. After mixing at 45 °C dilute with water. After filtration measure the intensity of the yellow coloured complex formed with the molybdovanadate reagent in nitric acid solution. Based on a calibration line of standard solutions the content of the P2O5 soluble in 2 % citric acid can be calculated. This value gives only an indication of the quality of the phosphates if it exceeds 95% solubility in both 2 % citric acid and ammoniumcitrate Petermann, it can be considered of good quality. However, it does not predict digestibility.
P2O5 soluble in water
Transfer an exact quantity of the sample in water. After mixing dilute with water. After filtration measure the intensity of the yellow coloured complex formed with the molybdovanadate reagent in nitric acid solution. Based on a calibration line of standard solutions the content of the P2O5 soluble in water can be calculated. This value does not give an indication of the digestibility. It can give an indication on the quality of mono-calciumphosphate. A mono-calciumphosphate of highest digestibility should be a least 80 % soluble in water.
