Conditioning period in HIC column

[qrys]

I work with silica particles that are coated with ethyleneglycol moieties. I silanized these silica in our lab. I noticed that for a new column there is a 'conditioning' period where it took several injections for the sample peak to achieve a constant height. Is this normal? if yes, why? I also read a paper that mentioned such behavior on their ethyleneglycol coated silica column, Im just wondering why.

Thanks

[tom jupille]

That's not an unusual problem in chromatography of proteins. Presumably there are some residual active sites (despite the silanization!) that are "eating" some of your sample.