OPA method modified by use of N,N-dimethyl-2-mercaptoethylammonium chloride as thiol component

Summary In the analysis of biological matrices, the application of o-phthaldialdehyde in the presence of a thiol component (OPA-method) for the quantitative determination of free - and -amino groups in amino acids, peptides and proteins as well as their hydrolytic or proteolytic products, respectively, is well known. The most frequently used thiol compound is mercaptoethanol. The use of this substance has the disadvantage that the initially generated isoindole often undergoes intramolecular rearrangement which often leads to a decrease in extinction at the monitoring wavelength of 340 nm. The present paper describes a modified method in which mercaptoethanol was replaced by N,N-dimethyl-2-mercaptoethylammonium chloride. The use of the new thiol component in the OPA reaction results in long-term stability of the extinction values (plateauing > 1 h). The modified method is further characterized by high accuracy and precision.

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Modifizierte OPA-Methode mit N,N-Dimethyl-2-mercaptoethylammoniumchlorid als Thiolkomponente