User:Carly M. Montanero/Notebook/CHEM-571/2013/09/11

Biomaterials Design Lab: Fall 2013

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Objective To finish the procedure from yesterday. Use the Atomic Absorption Spectrometer to test gold standards, citrate-AuNP solutions and BSA-AuNP solutions. Procedure There was an error in placing the cuvette in the UV-Vis, so all of our data from yesterday is incorrect. We created new standards and reran each sample, correctly using the UV-Vis. Today, we measured the concentrations in 10ml volumetric flask and the cuvette had a path length of 3cm. Standard solutions of gold and previously made standards of citrate-AuNP and BSA-AuNP were analyzed with the Atomic Absorption Spectrometer. Figures Atomic Absorption Data for Gold Standard, BSA-AuNP Standard, and Citrate-AuNP Standard Calculating the Number of Gold Atoms in Citrate-AuNP The equation of the best fit line from the class data was y = 3x10-5x2 + 0.0209x. The average of our corrected citrate-AuNP concentration was 0.1444 μg/mL. Setting 0.1444 equal to y yields the equation 0.1444 = 3x10-5x2 + 0.0209x. Solving the quadratic equation gives two answers: x = -703.51 and x = 6.842. Disregarding the negative value, the 6.842 μg/mL corresponds to the concentration of gold. We diluted the sample of gold by 10, so the actual concentration is 0.06842 g/L. The molecular weight of gold is 196.97 g/mol. Converting the concentration of gold to molarity yields a concentration of 3.474x10-4 M gold. Dividing the concentration of gold (3.474x10-4) M by the concentration of citrate-AuNP ( 9.17×10-9M) gives the final number of gold atoms per citrate-AuNP molecule. Though these calculations, there are 37,884 gold atoms per citrate-AuNP molecule. Notes The UV-Vis spectra of trial 4 Bradford Assay of horseradish peroxidase had some serious errors. We discarded the data.