Influence of twin-headed gemini micellar system on the study of methionine amino acid with ninhydrin in buffer solution

Abstract

The influence of double-headed gemini was examined in the present study by studying the amino acid methionine mixed with ninhydrin in CH3COOH-CH3COONa buffer solvent. The absorbance was monitored at fixed time intervals with UV-vis spectroscopy. An impact typical of surfactants was observed on the ninhydrin–methionine reaction and explained by a pseudo-phase model of micelles. The effect of different temperatures (343 to 363 K) was also determined. Based on data showing the impact of temperature on kψ, several relevant thermodynamic quantities, ΔH#, ΔS#, and Ea, were calculated using linear least-squares regression. In addition, the influence of the other reaction ingredients on the reaction, that is, pH and the concentration of ninhydrin and methionine, was studied. The CMC (critical micelle concentration) of pure geminis and the surfactant system with methionine and ninhydrin was evaluated at two temperatures, i.e. at 303 K and 353 K by conductivity measurements. The CMC values of pure gemini surfactants evaluated in the existing case at 303 K are concordant with the results stated before. Moreover, other parameters, including rates and binding constants, were calculated.

Keywords

• conductivity measurements
• double-headed geminis
• interfacial activity
• methionine
• spectrophotometer