Silver Nanoparticles Accumulate in Food Chain Nate Vetter Chem Professor Edgar Arriaga December 7, 2011

Problem Statement and Hypothesis Problem Statement  Silver nanoparticles are being used in wound dressings, catheters, and various household products.  Little research has been conducted to evaluate the impact of nanoparticles on terrestrial ecosystems Hypothesis  My hypothesis is silver nanoparticles can end up in the drainage, sewage, and waste water we expel which can make its way to the terrestrial ecosystems.  Insects can uptake these nanoparticles and the nanoparticles can translate up the food chain as predators eat the prey.

Overview  Main Analyte: Ag 0 Nanoparticles 5-20 nm  Limit of Detection: 2.0 to 7.0 μg kg −1  Matrixes: Waste Water, Soil, Plant Material, Worm Tissues Figure 1. Retrieved from Judy J. D. ; Unrine J. M. ; Bertsch P. M. Environ. Sci. Technol. 2011, 45,

Requirements for Successful Analysis 1)Must be able to detect small amounts of analyte 1)Low Limit of Detection 2)Must be able to detect small changes in analyte Concentration 1)High Sensitivity 3)Results must be reproducible and timely 1)High Precision 2)High Accuracy 3)Fast (minutes, not hours)

Studies Needed to Test Hypothesis  Identify Waste streams with nanoparticles present. Determine greatest area of concentration of silver nanoparticles.  Measure concentration of silver nanoparticles in soils near waste streams of interest.  Based on concentrations of silver nanoparticles found in soils, construct a study similar in the lab using concentrations below, at, and above to determine the effect on accumulation in worms.

Possible Separation Techniques TechniqueProsCons Ion-exchange Chromatography -Fast (minutes) -Low detection limit (ppm) -Other Ions can be detected -Only separation method is retention time -analyte must be charged Size Exclusion Chromatography (SEC) -Separation based on particle size -Fast -No physical or chemical interaction with analyte -Upper and lower limit to retention time -Possible irreversible adsorption of the particles by column packing material Capillary Electrophoresis (CE) -Very Fast analysis -Low detection limit -Expensive equipment

Possible Detection Techniques TechniqueProsCons Ultraviolet- Visible Absorption (UV-Vis) -Simple -Easy to use -Cheap -High Limit of Detection -Can have high signal noise -Requires Standards Atomic absorption Spectroscopy (AAS) -Low Limit of Detection -Can use solid sample -Requires Standards - Slow -Specialized Equipment Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS) -Low Limit of Detection -Can use solid sample -Highly Sensitive -Requires Standards -Specialized Equipment

Best Separation Technique: Ion- exchange Chromatography  Speed: Very fast (minutes)  It is a non-denaturing technique that can be used at all stages and scales of purification.  Selectivity: Can resolve molecules with small differences in charge.  Simplified Exchange Equilibrium: Figure 2. Retrieve from Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning: California, 2007.

Best Detector: AAS  Multi-element analysis  Limit of Detection: 0.1 – 100 pg  Reproducibility: 5-10%  High Sensitivity  Easy to use  Can buy commercially Figure 3. Retrieved From Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning: California, 2007.

Experimental Sample Preparation  Digestion/microcentrifuge - Using hydrochloric acid and hydrogen peroxide, digest the tissues of the worms or food source. Centrifuge the sample to extract the silver from the matix.  Vacuum Filter – Pores on filter should remove debris in sample but not impede nanoparticles.  Dry/Store – Rotovap to remove solvents and store at room temperature until needed

Possible Outcomes  Predicted Results:  Worms cannot shed the silver nanoparticles efficiently, resulting in concentration in tissues far exceeding that of their food source.  The results of this study should demonstrate trophic transfer and biomagnification of silver nanoparticles from a primary producer to a primary consumer.  The observation that nanoparticles can biomagnify highlights the importance of considering dietary uptake as a pathway for nanoparticle exposure. This raises questions about potential human exposure to nanoparticles from long-term land application of biosolids containing nanoparticles.

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