The objective for today was to complete various tasks in the lab, including:
- Test the accuracy of various pipettes
- Prepare solutions of NaCl and Rh6G dye
- Test reagent purities
- Prepare stock solutions
- Prepare 3 different PVOH films
1. Testing the accuracy of pipettes
4 different pipettes - P5000, P1000, P200, and P20 - were used and tested for accuracy. Different volumes of room temperature water were weighed and the mass was was compared to it's theoretical mass. A percent error was found to identify the accuracy of the pipettes. Results are found in Table 1.
2 a. Preparing solutions of NaCl
A 100mL of 1.71 mM NaCl solution was made by adding 0.0010 g of solid NaCl (MW: 58.44 g/mol) to 100mL of water, in a 100mL volumetric flask. The solution was mixed by repeatedly inverting the capped flask until the solid has dissolved.
2 b. Preparing solution of Rh6G dye
A 10mL of 13.5μM Rh6G dye solution was made using 277.5 μL of dye (MW: 479.01 g/mol, 233ppm conc.) to a 10mL volumetric flask. The remaining volume was filled with DI water. Note: since the flask was wet, it was first rinsed with DI water to ensure that any remaining wetness was instead the solvent we needed.
3. Test reagent impurities
We tested the purities of the fluorescence cuvette and the difference types of water we had. Testing using fluorescence was performed by adding DI water to a clean cuvette (i.e. creating a water blank) and testing to see if there was a fluorescent peak, indicating a fluorescent impurity. To test the quality of the water, we tested the conductivity of DI, tap, HPLC, and LC-MS water. Results are found in Table 2.
4. Preparing stock solutions
The following stock solution protocol was used for each respective stock solution:
- 100 mL 200 ppm Malachite Green Chloride (MW: 364.91 g/mol) solution was created was adding 20mg of malachite green chloride to 100mL of DI water.
- 100 mL 3 wt% bentonite
- A solution of 40 g Na2SO4, 4 mL H2SO4 (conc.), to 200 mL water.
- A 250 mL 1.0 M HCl (stock: 12.1 M) solution
- A 250 mL 0.2 M sodium bicarbonate solution using 4.2g of solid sodium bicarbonate (MW 84.01 g/mol) in DI water
5. Preparing PVOH films
Films of polyvinyl alcohol (PVOH, or PVA) were created using the following protocol:
- 3 quantities of 1 g of PVOH was added to 3 seperate small beakers with 12g of DI water.
- The solutions were heated, while covered with a watch glass, at around 70°C. The solutions were heated ans stirred until each PVOH crystal has been dissolved.
- While heating, 0.5mL of 8% glutaraldehyde was added to the first beaker, 0.5mL of 8% glutaraldehyde was added to the second beaker along with 0.1 g of bentonite, and 1mL of 8% glutaraldehyde was added to the third beaker.
- After the crystals were completely dissolved and the necessary reagents were added to the 3 beakers, the solutions were transferred to separate Teflon dishes and placed in the fume hood.
Data and Observations
This table illustrates the accuracy of the 4 pipettes tested. The most accurate pippete was the P5000, and the least accurate was the P1000.
This table illustrates the conductivity of the 4 various types of water tested. DI water was shown to be the most pure with the smallest presence of ions.