Mercaptoethanesulfonic acid as the reductive thiol-containing reagent employed for the derivatization of amino acids with o-phthaidialdehyde analysis

Mercaptoethanesulfonic acid (MES-OH) can be applied for hydrolyzing proteins. The aim of our research was to examine if it can be used also as a derivatization reagent for fluorescens detection of amino acids together with OPA (o-phthaldialdehyde) instead of ME (mercaptoethanol) owning to its thiol-group. Corn, soybean and meatmeal samples were hydrolized with hydrochloric acid or MES-OH, derivatized with ninhydrin or OPA/ME or OPA/MES-OH and analysed with IEC (ion exchange chromatography) or RP-HPLC (reversed phase high performance liquid chromatography). There were no significant differences among the amino acid composition results of samples irrespective of choice of the hydrolysis or derivatization methods. MES-OH can be applied not only for hydrolysis but also for derivatization of amino acids. In case of samples with high protein content (>50%), due to the dilution after hydrolysis the MESOH concentration could be insufficient for derivative formation, in these cases an extra MESOH addition is required prior to derivatization.