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Objective

Create new solutions of Malachite green dye of varying concentrations. Measure the absorbance of the solutions with UV-Vis.

Lab Protocol

1. Create two new solutions of Malachite green dye from the appropriate standard solution.
2. Measure the absorbance of Malachite green solution.

Procedure for cleaning cuvette

1. UV-Vis is a non-damaging technique. Replace your sample in the proper container using a pipette.
2. Rinse cuvette with water
3. Rinse cuvette with sodium dodecyl sulfate (SDS) solution
4. Rinse cuvette with water
5. Rinse cuvette with 10% HCl solution
6. Rinse cuvette with water

Data

1. Stock solutions
   1. 4.78 ppm (3.79083 g of 63.1 ppm Malachite green stock, water added to a total mass of 50.0521 g)
   2. 2.59 ppm (4.75639 g of 26.8 ppm Malachite green stock, water added to a total mass of 49.2598 g)
   3. 1.03 ppm (1.86080 g of 26.8 ppm Malachite green stock, water added to a total mass of 48.6527 g)
   4. 0.637 ppm (1.1903 g of 26.8 ppm Malachite green stock, water added to a total mass of 50.0786 g)
2. Calculations of new solutions (theoretical)
   1. 6.00 ppm (4.75 g of 63.1 ppm Malachite green stock, water added to total mass of 50 g)
   2. 0.10 ppm (7.85 g of 0.635 ppm Malachite green stock, water added to total mass of 50 g)
3. Calculations of new solutions (actual)
   1. 6.01 ppm (4.76174 g of 63.1 ppm Malachite green stock, water added to a total mass of 50.02011 g)
   2. 0.100 ppm (7.8702 g of 0.637 ppm Malachite green stock, water added to a total mass of 50.08441 g)

Figure 1: This is a graphical representation of the UV-vis absorbance of Malachite green standard solutions versus wavelength.

Figure 2: Standard curve of Malachite green peak absorbance at 617 nm versus the concentration of the solution.

Notes

Standard curve has a bad fit, so data was rerun on 2019/09/05.