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Enhancing Chemistry Labs with Ion-Selective Electrodes: A Cost-Effective Approach

Discover the benefits and applications of Ion-Selective Electrodes (ISEs) in the chemistry laboratory, with practical insights on incorporating ISEs into experiments. Learn about their history, usage in the "Water Project," and student assignments. Explore electrode manufacturing processes and student calibration results for enhanced learning outcomes.

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Enhancing Chemistry Labs with Ion-Selective Electrodes: A Cost-Effective Approach

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  1. ISE: A cost effective way to add ion selective electrodes to the general chemistry laboratory experience. Steven L Brown & Cynthia Runkel Department of Chemistry University of Arizona

  2. Why Teach ISEs? • Introduction to sensor technology • An affordable instrumental technique • Demonstration of electrochemical measurement

  3. How We Use ISEs • Measurement of [Ca2+]. • One component of the “Water Project”. • Available for Cu2+ or Pb2+ for the Make-your-own-ISE project.

  4. History of Gen Chem ISEs at Arizona • Early 80’s added an experiment using wire-coated PVC electrodes. • By early 90’s, replaced with “store bought electrodes”. • In 2001, commercial electrodes replaced with PVC film electrodes.

  5. The Water Project • Students use four techniques over three weeks to create a cation profile of water samples they provide. • ISEs are used to determine [Ca2+].

  6. Assignment • Students prepare a series of standards. • Students measure standards and samples. • Plot results and determine [Ca2+] concentration.

  7. The Electrodes • Use IJ ISE Combination Ion Electrode manufactured by Ionode PTY LTD of Tennyson, Brisbane, Australia. • Bodies contain a Ag/AgCl reference electrode and an open end. • Tips are made by preproom staff. • Open tube filled with “filling solution” and covered with a tip.

  8. Manufacture • Cut Tygon tips • Make “cocktail” • Dissolve PVC in THF • Add plasticizers and ionophores • Tips dipped and allowed to dry • Re-dipped twice more. • Tips inspected for bubbles. Bad tips discarded. • Completed tips stored in jar (no special conditions required). • Electrodes assembled as needed.

  9. Fluka Our source for the cocktails recipies and the cocktails to make them is Fluka. http://www.sigmaaldrich.com/Brands/Fluka___Riedel_Home/Analytical/Sensoric_Applications.html#iono

  10. Calcium Cocktail Contents

  11. Financial Cost

  12. Manpower costs • Time required to make 40 tips – xxx employee hours • Pre-calibration time – 0 hours

  13. Reliability • 40 tips made in the Spring • 30 of these are still usable in the Summer • 25 are still usable in the Fall

  14. A good student result

  15. Student Calibration Results

  16. Linearity of student plots • 42 with R2 values less than .9900 • 49 with R2 values greater than .9900

  17. Average Normalized Student Calibration Plot

  18. Average results from pCa2+ 2 to 4

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