[mahesh]

I have seen some literature on silica determination from effluent samples. There are three kinds of silica in the samples- reactive, colloidal and suspended particles (e.g., sand), with the reactive being that portion of the total dissolved silica that is readily reacted in the standard molybdate colorimetric test, and the colloidal being that which is not.
I want to determine the suspended silica in my sample. We can assume that I am not having reactive or suspended form, but only the colloidal form.
Does anyone know or can suggest some methodology to determine the colloidal silica?

[enahs]

A little to vague. You can do your titration test and get that information, and then subtract that from the information of total silicon you would get if you put the sample on an ICP. But that requires having an ICP, which are not cheap. Or on a mass spec.

The point is yes there are plenty of ways; how do you need to do it.

[mahesh]

Dear Enahs,
let me be more specific. The ASTM D 859 method gives the details of a quantitative method for the determination of silica which is 'molybdate reactive'. The term, as described on the webpage, explains that this form of the silica includes- dissolved simple silicates, monomeric silica and silicic acid, and an undetermined fraction of polymeric silica.
Now I know we can determine total Si in the sample with ICP, and then substract the silica determined by the molybdate method from the total silica to get the colloidal silica.
However, I wanted to see if there exists (or is proposed) a method for the direct determination of colloidal silica from a sample.
I hope I am more clear with my query this time, thanks.