Method 62ai Determination of watersoluble phosphorus autoanalysis

Procedure. Pipette 1 ml of the AOAC extract (increase appropriately if the peaks are too small) into a 20-ml volumetric flask. Using a pipettor, carefully add 1 ml H2SO4 (approximately 98% m/m), swirl slowly to mix and allow to cool. Make up to the mark with 50% (v/v) H2SO4 (approximately 98% m/m), stopper and invert several times to mix. The water soluble P, present in the sample solution as orthophosphate, can be determined by autoanalysis; see Chapter 7 for details of standards, reagents and method.

For the SI 1996 No. 1342 extract, pipette 1 ml of the extract (increase appropriately if the peaks are too small) into a 50-ml volumetric flask. Using a pipettor, carefully add 1 ml H2SO4 (approximately 98% m/m), swirl slowly to mix and allow to cool. Make up to the mark with 50% (v/v) H2SO4 (approximately 98% m/m), stopper and invert several times to mix. The water soluble P, present in the sample solution as orthophosphate, can be determined by autoanalysis; see Chapter 7 for details of standards, reagents and method.

Calculation. For both the AOAC and SI 1996 No. 1342 extracts, divide the concentration of phosphate-P in the diluted sample (read from the standard curve) by 2 to obtain the percentage water-soluble P in the sample. If 2 ml (instead of 1 ml) extract were diluted to 20 ml, divide by 4, and so on. If required, multiply the % P by 2.2915 to obtain the % P2O5.

0 0

Post a comment