I precipitated the protein in serum (spiked with ethylene glycol, diethylene glycol, triethylene glycol and 1,2 butanediol) with methanol. The supernatant was dried and incubated with 100 uL BSTFA with 1% TMS at 75 deg C. Some crystal was formed.

The crystal was not formed all the time but instead in some samples only. The serum matrix was from the same pooled source.

Could anyone explain the formation of crystal please?

Thanks.