Presentation on theme: "ISE: A cost effective way to add ion selective electrodes to the general chemistry laboratory experience. Steven L Brown & Cynthia Runkel Department of."— Presentation transcript:
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 Demonstration of electrochemical measurement
How We Use ISEs Measurement of [Ca 2+ ]. One component of the “Water Project”. Available for Cu 2+ or Pb 2+ for the Make- your-own-ISE project.
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.
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 [Ca 2+ ].
Assignment Students prepare a series of standards. Students measure standards and samples. Plot results and determine [Ca 2+ ] concentration.
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.
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.
Fluka http://www.sigmaaldrich.com/Brands/Fluka ___Riedel_Home/Analytical/Sensoric_Appli cations.html#iono http://www.sigmaaldrich.com/Brands/Fluka ___Riedel_Home/Analytical/Sensoric_Appli cations.html#iono Our source for the cocktails recipies and the cocktails to make them is Fluka.
Calcium Cocktail Contents ChemicalAmountCost per 5 mL cocktailPer tip Poly(vinyl chloride) 250g$27.80$0.20$0.01 Tetrahydrofuran 1000ml$30.10$0.15$0.01 Calcium ionophore IV 250g$678.90$0.30$0.01 2-Nitrophenyl octyl ether 25ml$120.50$2.41$0.06 Potassium tetrakis(4- chlorophenyl)borate 1.00g$134.00$0.40$0.01