I am analysing inorganic phosphorous in soymilk by a colorimetric method ( with Fe2So4 and amonium molibidate). The results obtained are up to the total P for this product. Might low pH release P from phytate? Are there any interferents for this reaction? I've already done recovery tests, which were ok.
But one doubt that I have is, if the pH does release inorganic phosphorus from phytate, why do we need to use phytase, if low pH releases P? Isn't our stomach HCL enough to provide available phosphorous from phytate molecules?
Low pH can cause release of orthophosphate from labile organic substances such phosphoesters and probably phytase, however I did not observe such release. Furtermore, barium, lead, and silver interfere by forming insoluble phosphates, but the effect is usually negligible in natural-water samples. Interference from silicate, which also can form reduced heteropoly acids with molybdate, is negligible under reaction conditions reported by Murphy and Riley (1962; controlled pH and time reaction). Arsenic as arsenate ion (AsO4-3) produces a color similar to that of phosphate and might cause a positive interference. According to Murphy and Riley (1962), concentrations of As (V) up to 100 ug/L do not interfere.
ı agree wıth ıngrıd and ı use thıs coloremetrıc method alot wıth no ınterfernce
you can determıne the phosphorus content ın one sample by usıng ICP or atomıc adsorpatıon and compare the result
I'd like to thank you two very much for your comments. They were really helpful for me. Kind regards, Luciula
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