Kinetic–spectrophotometric approach to the ampicillin hydrolytic degradation applied for the histidine determination

Abstract

The objective of this research was to develop a kinetic-spectrophotometric method for the determination of microquantities of L-histidine in pure form and dietary supplements. The method was based on the kinetics of ampicillin degradation by Ni(II) ion as a catalyst in the presence of L-histidine in a strongly alkaline medium. The rate of this reaction was monitored spectrophotometrically by measuring the increase in absorbance at 265 nm as a function of time. The same approach was used for the investigation of the reaction rate in the absence of histidine. A differential variant of the tangent method was used to process the kinetic data. Beer?s law was obeyed in the interval of histidine concentration from 1.24 ?g/ml to 11.63 ?g/ml with the relative standard deviation ranging from 8.1% to 0.7%. The detection limit of 0.46 ?g/ml was estimated based on the 3S0 criterion. The interference effects of some metal ions, anions, and other molecules on the reaction rate were studied to assess method selectivity. Herein described method was applied for the quantification of histidine in dietary supplements. The point hypothesis test confirmed that there was no significant difference between the proposed and the reference method.