Determination of total phosphorus in plant material and feeding stuffs

Discussion 7.10. Determination of total phosphorus in plant material and feeding stuffs 

The AOAC alkalimetric ammonium molybdophosphate and photometric molybdovanadate methods for animal feed are described by Padmore (1990, pp. 87-88), and for plants by Isaac (1 990, p. 56). A spectrophotometric molybdovanadate procedure is also described in MAFF/ADAS (1986, pp. 181-182). The official Bran-rLuebbe AutoAnalyzer method for phosphate in soil, plant and fertilizer extracts is reproduced with permission in Appendix 6. 

We will describe the autoanalysis method based on Faithfull (1971a) which uses the same Kjeldahl acid digest solution as that used for the nitrogen determination (see Discussion 7.7). The proper development of the yellow colour of the phosphovanadomolybdate complex is sensitive to the pH, 

Method 7.10a. Determination of totai phosphorus in piant materiai by autoanaiysis 

Procedure. The digestion procedure is given in Method 7.7a. The flow diagram is shown in Fig. 7.4. 

---