Prev. Article Next Article Table of Contents

Article

Weak Acid pKa Determination Using Capillary Zone Electrophoresis

Your current credentials do not allow retrieval of the full text.

Purchase the full-text

PDF/HTML,
figures/images,
references and tables,
(where available)

Mike Solow

Department of Chemistry, City College of San Francisco, San Francisco, CA 94112

J. Chem. Educ., 2006, 83 (8), p 1194

DOI: 10.1021/ed083p1194

Publication Date (Web): August 1, 2006

Section:

History, Education, and Documentation

Abstract

This article describes a general chemistry experiment designed to measure the pK_a of benzoic acid using capillary zone electrophoresis. Despite the fact that modern biology relies so heavily on this analytical technique, students get very little explanation of the principles of electrophoresis in many biology labs. This laboratory exercise is intended to introduce undergraduate students to capillary electrophoresis while stressing the role of acid–base chemistry. While there are certainly easier ways to find the pK_a of an acid (such as titration) this method requires only nanograms of the weak acid and is particularly well suited to analytes such as pharmaceuticals, herbicides, and pesticides that have low water solubility. In this experiment, students use capillary zone electrophoresis to determine the effective mobility of benzoic acid at two different hydrogen ion concentrations. A plot of these data yields the pK_a of benzoic acid. Student results using this method (pK_a = 4.23, RSD = 8.5%) are quite close to the literature value of 4.18.

Keywords (Audience):

First-Year Undergraduate / General

Keywords (Domain):

Analytical Chemistry

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Acids / Bases

View: Hi-Res PDF | PDF w/ Links

Citing Articles

View all 1 citing articles

Citation data is made available by participants in CrossRef's Cited-by Linking service. For a more comprehensive list of citations to this article, users are encouraged to perform a search in SciFinder.

This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Capillary Electrophoresis: Focus on Undergraduate Laboratory Experiments
Lisa A. Holland
Journal of Chemical Education2011 88 (3), 254-256
- Capillary Electrophoresis: Focus on Undergraduate Laboratory Experiments
  Lisa A. Holland
  Journal of Chemical Education2011 88 (3), 254-256
  Capillary electrophoresis is a versatile technique well suited to teach concepts that are fundamental to a chemistry degree program. The applicability of capillary electrophoresis to metabolites, DNA, proteins, pharmaceutical compounds, environmental ...
  Abstract | Full Text HTML | Hi-Res PDF | PDF w/ Links