Determination of sulfhydryl groups in ovalbumin by high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection.

High-performance liquid chromatography (HPLC) interface to inductively coupled plasma mass spectrometry (ICPMS) has been applied for the first time to determine the sulfhydryl groups (SHs) in chicken ovalbumin (OVA) after their conversion into mercaptides with organic mercury compounds. The procedure is based on the HPLC separation of mercury mercaptide OVA followed by ICPMS detection of mercury. The rates of reaction of five mercaptide-forming reagents with SHs in OVA were in the order ethylmercuric chloride > mersalyl acid > p-chloromercuribenzoate > p-(chloromercuri)benzenesulfonic acid > fluorescein mercuric acetate. Apparently the reaction rate is slowed by an increase in the steric hindrance around the mercury atom. The detection limit for SHs was lower than 1 pmol of OVA.