For my lab, we took different amino acid concentrations, mixed them with ninhydr
ID: 480618 • Letter: F
Question
For my lab, we took different amino acid concentrations, mixed them with ninhydrin, heated in a covered test tube, cooled, and measured the absorbance with a spectrometer. I am having a hard time with the analysis question. 1) what is the reason for cooling the sample to room temperature before measuring the absorbance? 2) are there any other byproducts of the ninhydrin-amino acid reaction that can be used to help detect the presence of amino acids? How can these byproducts be detected? 3) what is the concentration range over which amino acid is linear? Thank you! For my lab, we took different amino acid concentrations, mixed them with ninhydrin, heated in a covered test tube, cooled, and measured the absorbance with a spectrometer. I am having a hard time with the analysis question. 1) what is the reason for cooling the sample to room temperature before measuring the absorbance? 2) are there any other byproducts of the ninhydrin-amino acid reaction that can be used to help detect the presence of amino acids? How can these byproducts be detected? 3) what is the concentration range over which amino acid is linear? Thank you! 1) what is the reason for cooling the sample to room temperature before measuring the absorbance? 2) are there any other byproducts of the ninhydrin-amino acid reaction that can be used to help detect the presence of amino acids? How can these byproducts be detected? 3) what is the concentration range over which amino acid is linear? Thank you!Explanation / Answer
For the analysis of amino acid with ninhydrin
(a) sample is cooled prior to analysis : ninhydrin undergoes reduction when reacted with alpha-amino acid and gives off a water molecule. Under heated condiiton the released H2O may react with the alpha-amino acid, hydrolyzes the amine group to keto and forms alpha-keto acid and NH3 molecule. This then under heated condition undergoes decarboxylation to an aldehyde and CO2. To avoid this decarboxylation, the system is cooled before analysis.
(b) The reaction also produces alpha-keto acid which may be analyzed by formation of DNP derrivative which are highly colored compounds of ketone functionality.
(c) Concentrations range for 0.1-0.5 generally follow the beer's law and we would get a linear graph. this however also depends upon the type of sample under study.
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