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

Biomaterials Design Lab: Fall 2013 Main project page
Previous entry      Next entry

## 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

1. The equation of the best fit line from the class data was y = 3x10-5x2 + 0.0209x.
2. The average of our corrected citrate-AuNP concentration was 0.1444 μg/mL.
3. Setting 0.1444 equal to y yields the equation 0.1444 = 3x10-5x2 + 0.0209x.
4. Solving the quadratic equation gives two answers: x = -703.51 and x = 6.842.
5. Disregarding the negative value, the 6.842 μg/mL corresponds to the concentration of gold.
6. We diluted the sample of gold by 10, so the actual concentration is 0.06842 g/L.
7. The molecular weight of gold is 196.97 g/mol.
8. Converting the concentration of gold to molarity yields a concentration of 3.474x10-4 M gold.
9. 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.
10. Though these calculations, there are 37,884 gold atoms per citrate-AuNP molecule.