To the best of my knowledge this is an impossibility. Anything that will react with an SH or OH group on an organic molecule will also react with water.
In other words, there are no existing silylation reagents which are water stable, even the tris(trimethylsilyl)silane "super-silyl" reagents? It does not necessarily have to be a silyl halide...
I wonder if OP can do a neat reaction as opposed to an aqueous one at least. There may be essentially neat silylation procedures possible. Or even heterogeneous!
Unfortunately no, it has to be done in aqueous solution...
Could you give us some more details of the problem at hand? It sounds interesting but to suggest even a work around we need data.
In essence it's not a synthetic issue, but I wanted to ask the question here since derivatization could be viewed as "protection" in some cases, and some experience I gained during my MSc studies tells me that organic chemists might have a good advice.
I'm trying to develop a GC method for quantification of a couple of drug metabolites which are found in urine. They contain only alkyl chains, a thiol group and a keto group (γ to the thiol). I might always dissolve the pure standard in an organic solvent and derivatize the thiol group for calibration purposes. However, I need a reagent for protection of these thiols within
the urine sample (that's why aqueous solution) while avoiding any sample prep steps like LLE, SPE etc.
Selectivity should not be an issue here. The derivatizing/protecting reagent can bind to other components of urine, but these should later be separated and the target compounds identified easily by GC-MS/MS.