I am doing a column experiment in saturated porous media, using different P concentration effects on the transport of ferrihydrite colloids. I got a 5 ml effluent for every sample. I divided that in two parts. The 2.5 ml I used for measuring soluble P after centrifuge and filtration with 0.22 um filter membrane and measured via Murphy and riley method. while for TOTAL PHOSPHORUS, I took 1 ml of effluent and digested with 4 ml of 6M HCL for 24 hrs as per the digestion process for ferrihydrite colloids described in literature and then I used p-nitrophenol indicator (yellow indicator) and neutralized sample with 4M NaOH and 0.1 HCl. and then after neutralizing the sample I measured total P with murphy and riley (1962) method. My question is that, Is that the right way of measuring total P? I got good results by the way but need opinion from experts...
@ Tufail, if you are satisfied with the results you are getting then it is Ok. Otherwise, I suggest to use Olsen and Sommers (1982) soil total phosphorus determination method where total P measurements involves digestion of soil samples with a strong acid ( perchlioric acid and nitric acid if needed) and the dissolution of all insoluble inorganic forms (including plant available P fraction) and organic P forms.
J. C. Tarafdar Sir, Im not measuring total P in soil samples. its a Phosphorus sorbed ferrihydrite colloid transport effluent passing through column.
Paul Milham Respected Prof, Thanks for your answer.. But would you suggest any other method? or you think I should carry on with this..
You can carry on the current method. However you should check your results by using a reference materials. Or at least prepare a ferihiydrite with known P to conform the accuracy and precision of your procedures.
Veli Uygur Yes Sir, I prepared ferrihydrite with different concentrations of P, and confirmed. but I didn't find a suitable reference for my work i.e. the digestion of P sorbed iron colloids, the way I did.
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