Dl homocysteine thiolactone hydrochloride

Cytochrome c (from bovine heart), lysozyme (from chicken egg white), alpha lactalbumin (from bovine milk), DL-homocysteine thiolactone hydrochloride (HTL) and 8-Anilinonaphthalene-1-sulphonic acid were purchased from Sigma-Aldrich chemical Co. Potassium chloride, di-potassium hydrogen phosphate and potassium di-hydrogen phosphate were purchased from Merck, India. Dithiobis(2-nitrobenzoic acid), the Ellman's reagent was also purchased from Sigma-Aldrich chemical Co. Guanidium hydrochloride (Gdmcl) was purchased from M.P. Biomedicals. Unless otherwise stated, all chemicals were used without further purification and double distilled water was used as aqueous phase.

Sodium hydroxide (NaOH), sodium hydrogen phosphate (Na₂HPO₄), toluene (C₆H₅CH₃) and chloroform (CHCl₃) were from POCH (POCH, Gliwice, Poland). Phosphoric acid (H₃PO₄), dichloromethane (CH₂Cl₂) and methanol (CH₃OH) were purchased from J.T. Baker (J.T. Baker, Deventer, Netherlands). Octadecyltrimethoxysilane (ODTS), ethyl acetate (CH₃COOCH₃) and d,l-Homocysteine thiolactone hydrochloride were received from Sigma (Sigma, St. Louis, MO, USA). To prepare stock standard solution of HTL (final concentration 0.1 mol/L) an appropriate amount of this compound was dissolved in water. All buffers needed for CE analysis were filtered through 0.2 μm pore size membranes. The pH values of the buffers used for CZE separation and sample preparation were adjusted by potentiometric titrations. The pH-meter was calibrated with standard pH solutions.