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Spectrophotometric Determination of the Dissociation Constant of an Acid-Base Indicator Using a Mathematical Deconvolution Technique
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Abstract
A laboratory experiment that uses a spectrophotometric method to determine the apparent acid-dissociation constant (Ka') of neutral red, a common acid–base indicator, has been developed. The experiment incorporates a unique data analysis technique using a mathematical deconvolution program that allows students to resolve distinct spectral components within complex absorbance spectra. After measuring the neutral red absorbance over a range of pH values, students quantify the acidic and basic forms of the indicator present in each solution, correct for differences in the molar absorptivities of each species, and determine the Ka′ of the indicator. This laboratory exercise gives students an opportunity to use advanced data analysis techniques and to observe directly how the spectral characteristics of an acid–base indicator are affected by the solution pH.
Keywords (Audience):
Upper-Division UndergraduateKeywords (Domain):
Laboratory InstructionKeywords (Pedagogy):
Hands-On Learning / ManipulativesKeywords (Subject):
Acids / BasesCiting Articles
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This article has been cited by 1 ACS Journal articles (1 most recent appear below).
Measuring Binding Affinity of Protein−Ligand Interaction Using Spectrophotometry: Binding of Neutral Red to Riboflavin-Binding Protein
Pirom Chenprakhon, Jeerus Sucharitakul, Bhinyo Panijpan, Pimchai ChaiyenJournal of Chemical Education2010 87 (8), 829-831Measuring Binding Affinity of Protein−Ligand Interaction Using Spectrophotometry: Binding of Neutral Red to Riboflavin-Binding Protein
Pirom Chenprakhon, Jeerus Sucharitakul, Bhinyo Panijpan, Pimchai ChaiyenJournal of Chemical Education2010 87 (8), 829-831The dissociation constant, Kd, of the binding of riboflavin-binding protein (RP) with neutral red (NR) can be determined by titrating RP to a fixed concentration of NR. Upon adding RP to the NR solution, the maximum absorption peak of NR shifts to 545 nm ...
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- Received: August 03, 2009
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