B DETERMINATION OF TOTAL PHOSPHORUS BY SFA

1 Orthophosphates form a yellow-coloured complex with molybdate ions in an acid medium. After addition of ascorbic add and Sb, a blue-coloured phosphomolybdenum complex is formed, of which the absorbance is measured at a wavelength of 660 nm. The determination is carried out as a so-called segmented-flow analysis (SFA). 

2 This determination may be carried out on digest 2.1 (digestion with H SO., - salicylic add - HPj - Se) and digest 2.2 (digestion with H SO., - salicylic acid - Hp )- 

Sb is added to complete the reduction of the yellow phosphomolybdenum complex to the blue 

1 This procedure yields a standard curve that is linear up to approximately 60 mg/L 

2 The detection limit is approximately 0.05 mg/L in the digest. The determination limit is approximately 0.15 mg/L (0.8 mmol/kg in the dried plant material). 

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