Discrimination of Complex Mixtures by a Colorimetric Sensor Array: Coffee Aromas

Benjamin A. Suslick, Liang Feng and Kenneth S. Suslick*
University Laboratory High School, University of Illinois at Urbana−Champaign, 1212 W Springfield Ave., Urbana, Illinois 61801, and Department of Chemistry, University of Illinois at Urbana−Champaign, 600 S. Mathews Ave., Urbana, Illinois 61801
Anal. Chem., 2010, 82 (5), pp 2067–2073
DOI: 10.1021/ac902823w
Publication Date (Web): February 9, 2010
Copyright © 2010 American Chemical Society
* Corresponding author. Tel: 1-217-333-2794. Fax: 1-217-333-2685. E-mail: ksuslick@uiuc.edu., †

University Laboratory High School, University of Illinois at Urbana−Champaign.

, ‡

Department of Chemistry, University of Illinois at Urbana−Champaign.

Abstract

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 °C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures.

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History

  • Published In Issue March 01, 2010
  • Article ASAPFebruary 09, 2010
  • Received: December 11, 2009
    Accepted: January 26, 2010

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