P SEUDO -Z ERO - O RDER K INETICS : D IFFUSION THROUGH A P OLYMER M EMBRANE U SING A S ATURATED S OLUTION R ESERVOIR S YSTEM Jan-alfred Aquino | Christopher Chen | Yanglu Chen | Zachariah DeGiulio | Katherine Dong | Christina Floristean | Michelle Guo| Alexandra Kapadia | Robert Kolchmeyer | Erik Massenzio | Adam Richardson | Jessica Xu Dr. David Cincotta | Alberto Rivera

Controlled Release Zero-order kinetics Rate independent of concentration Does not often occur in nature Applications: o Medicine o Agriculture o Cosmetics

Pseudo-Zero-Order Kinetics Fick's Law: A pseudo-zero-order system would achieve a constant rate of release, but would not be independent of concentration. This can be done by holding the concentration gradient constant.

Hypothesis IF: An apparatus is made that allows for diffusion of a saturated solution into a body of water across a membrane THEN: Pseudo-zero-order diffusion should be observed Maintain a constant concentration gradient

Polymer Membrane Repeating structural units of monomers Amorphous structures more easily allow diffusion than crystalline structures Ethylene-vinyl acetate o 10% EVA o 12% EVA

Choosing Citric Acid Solid at room temperature Chosen over maleic acid and sodium chloride Conductivity & pH probe Continuously measured over longer periods of time Most consistent results Citric acid Maleic acid

Experimental Design: Saturated Solution Reservoir System Saturated solution of citric acid added to petri dishes Solute passes through the membrane Additional solid citric acid added to continuously re- saturate the solution Pseudo-zero-order Polymer Membrane Saturated Solution Solid Citric Acid Petri Dish Water Basin

Final Setup

Experimental Design Design Features: Water-tight petri dishes Petri dish supports Maximize water and solution contact with the membrane Surface area optimization Uniform water level with respect to the petri dish

Results - The Diffusion of Citric Acid across a 10% EVA Membrane

Results – The Diffusion of Citric Acid Across 10% and 12% EVA Membranes With additional solute 10% EVA (top graph) 12% EVA (bottom graph) Suspected pH meter issue resulting in a few nonlinear curves 10% EVA Trials 12% EVA Trials

Results – The Diffusion of Citric Acid Solution Across 12% EVA 12% EVA with 2g solid Trials with 2g extra solid are zero order

Discussion Rate was faster in first few hours Tested with 10% EVA and 12% EVA Polarity accounts for permeation Reproducible rates remain elusive

Conclusion Achieved pseudo-zero-order kinetics with reservoir system Polar likes polar: Citric acid diffused through 12% EVA more effectively than 10% EVA Novel method for modeling a controlled-release system Data was supportive of hypothesis More needs to be done to conclusively accept or refute the hypothesis

Future Studies Explore alternate methods of measuring diffusion Solute embedded in polymer Biodegradable polymers Solute with lower solubility Mathematical models based on parameters of polymer membrane and solute Generalized curve fits

References 1. Prisciandaro M. and Pepe F. Absorption with zero and Pseudo-Zero order chemical reaction. The Canadian Journal of Chemical Engineering; (2006) [Internet] [accessed July 29, 2011] 362 – 368p.. Available from : Nic M., Jirat J., Kosata B. Compendium of Chemical Terminology. IUPAC Goldbook; (2006).[Internet] [ accessed July 27, 2012] Available from : Blackmond DG., Hodnett NS., Lloyd-Jones GC., Mechanistic Implications of Pseudo Zero Order Kinetics in Kinetic Resolutions. JACS Communications; (2006). [Internet] [accessed July 29, 2011] p. Available from : Jones D. FASTtrack: Pharmaceutics: Dosage Form and Design. London: Pharmaceutical Press; (2008). [Internet] [accessed 2012] Available from : 5. Basic Property of EVA Resin. SNE Research; (2006) [Internet] [accessed July 26, 2012] Available from : Ionization Constants of Heteroatom Organic Acids. Michigan State University. [Internet] [accessed July 26, 2012] Available from : Material Safety Data Sheet - Citric Acid. Science Lab. [Internet] [accessed July 24, 2012] Available from : Periodontics: Controlled release delivery system. British Dental Journal; (2003). [Internet] [accessed July 30, 2012] p. Available from : 9. Controlled release of triprolidine using ethylene-vinyl acetate membrane and matrix systems. European Journal Pharmaceutics and Biopharmaceutics. (2002) [Internet] [accessed 2012] p. Available from : Gupta C., Chauhan A.Drug transport in HEMA conjuctival inserts containing precipitated drug particles.Journal of Colloid and Interface Science ; (2010). [Internet] [accessed July 30, 2012] p. Available from : Drabczyk K., Panek Piotr. A Comparative Study of EVA with and without thermal history for different lamination process parameters. Material Sciences and Engineering: B; (2011). [Internet] [accessed July 29, 2012] Available from : Krishnan KA., Sreejalekshmi KG., Varghese S. Adsorptive Retention of Citric Acid Onto Activated Carbon Prepared From Havea Braziliansis Sawdust: Kinetic and Isotherm Overview. Desalination; (2010). [Internet] [accessed July 30, 2012] p. Available from :

Acknowledgements Dr. David Cincotta, Advisor Alberto Rivera, Assistant Dr. David Miyamoto, Director New Jersey Governor's School in the Sciences and its Sponsors