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Steven L Brown & Cynthia Runkel Department of Chemistry University of Arizona

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. Why Teach ISEs?. Introduction to sensor technology An affordable instrumental technique

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Steven L Brown & Cynthia Runkel Department of Chemistry University of Arizona

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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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