Ifeoluwa Faleke Lab Performed: 2/2/17 Biology 2112 Lab Lab Due: 2/9/17 TA: Dr. Taheri Lab 2: Techniques of Measurement The purpose of this lab was to get us acquainted with the spectrophotometer. We made a stock solution and then made 5 different dilutions from it. Then, we had to find the right wavelength on the machine and zero it, and after, we found the absorbances of the 5 dilutions plus 2 unknowns and 2 mixtures. Exercise 1: Preparation of a Stock Solution of NaCl in H 2 O We need: a. Two 100 ml graduated cylinders labeled A and B b. 50 ml of H 2 O c. Pipette d. Stirring bar e. 15 gm of salt (NaCl) f. Weighing paper g. Scale Procedure: 1. Add 50 ml of H 2 O to both cylinders A and B (use pipette to add last couple ml) 2. Add stirring bar to H 2 O in cylinder A and place on center of stirring base. (Note change in volume level) 3. Weigh 15 gm of salt (NaCl) on weighing paper (remember to tare scale) 4. Slowly stir H 2 O in cylinder A and gradually add NaCl to it. Stir until dissolved. 5. Stop the solution from stirring. Gradually add H 2 O from cylinder B to cylinder A until the volume reaches the 100 ml mark. Resume stirring until thoroughly mixed. (Called “bringing the solution to volume”). Exercise 2: Use of the Spectrophotometer We need: a. Spectrophotometer b. 3 cuvets c. Kim Wipes
Procedure: 1. Fill one cuvet with distilled water and wipe outside with kim wipe. Set instrument to 600 nm. Place cuvet in spectrophotometer with white line towards you and “zero” the instrument (adjust to 0 absorbance). Now give the cuvet a ¼ turn and see if you get a different reading. Give a ¼ turn twice more and check the readings. 2. Remove your cuvet and pass it around so that all the members of your group can handle it. Get greasy finger prints on it. Repeat step 1. 3. Wipe the cuvet clean and “zero” the instrument. Fill the other two cuvets with distilled water and take readings (keep white line on cuvet toward you). 4. Use one cuvet with distilled water in it as a blank and into another cuvet place a dilution of Coomassie Blue. Zero instrument with the water blank, read your sample and record result, account for differences between cuvets in step 3. Read your sample on other spectrophotometers in the lab.
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- Spring '06
- pH, cuvets