Dionex used to make a system for SiO2, but I'm pretty sure they used a Molybdenum color reaction and ran it through an absorbance detector. It was capable of Part Per Trillion detection though. I don't believe there is a way to do it with standard Ion Chromatography.

Dissolved silica can be measured in solution as silicate using ion chromatography. As the anion of a weak acid, silicate is generally poorly retained by anion exchange columns. Because it has almost no dissociation at pH 7, the ion cannot be determined by suppressed conductivity detection. As a weak acid, it is adequately retained by anion exchange, eluting later than fluoride. Silicate can be derivatized post-column with sodium molybdate reagent to form a complex that can be detected with high sensitivity by visible absorbance at 410 nm. This acidic reagent will also react with phosphate to form a complex that is detectable at the same wavelength.

Regards

Please Ref PE Jackson 2000. Nicely described the technique and other details.