Guanidinium chloride + PBS/N3 -> jelly?

[WS]

Just called the company where I had bought that stuff. They confirmed
that 0.3% silica are added as anti-caking agent to their "technical
grade" quality. They suggested that, for biochemical experiments, one
might buy their biochem grade. Oh-no! By far too expensive. Actually,
what are technical application of GuHCl if not cleaning of sephadex
columns?

Wo