User:Melissa Novy/Notebook/CHEM-572/2013/02/06

Objectives

• Make 50 mL 5 M KNO₃ solution for ionic strength adjustments with silver ion-selective electrode.
• Make agar solution and plate E. coli cells.
• Analyze cells with UV-vis spectrophotometry.
• Make PLA2002D + 5wt% Laponite (PLA + 5LMT) using dichloromethane.

Agar Solution and Agar Plates

• The plates made on 2013/01/30 were unusuable, so the plates were remade using the same protocol as before.
• However, modifications to the recipe were as follows:
  • 12.5 g Teknova LB medium
  • 7.5 g ??? agar

Calculations for 5 M KNO₃

  MW KNO3: 101.10 g/mol
  0.050 L × 5 M KNO3 = 0.25 mol KNO3
  0.25 mol KNO3 × (101.10 g/1 mol KNO3) = 25.275 g KNO3

• Actual mass KNO₃: 25.2756 g
• Actual molarity KNO₃: 5.00 M
• KNO₃ was placed in a glass screw-top bottle and 50 mL of pure H₂O was added. The solution was stirred and heated at 70°C for 3 hours to dissolve the KNO₃.

PLA2002D + 5wt% Laponite Film

• 1 g of PLA was dissolved in 10 mL of dichloromethane in a fume hood.
• 0.05 g Laponite was dispersed in 5 mL of dichloromethane, and then added to the PLA solution.
• The solution was stirred for 1 h and then cast into a Teflon dish.
• The dish was left under the fume hood to encourage evaporation of the dichloromethane.

UV-Vis on E. coli Cells

• Absorbance was measured at 650 nm with a Shimadzu UV-1800 spectrophotometer using plastic cuvettes. 2 mL of each sample was pipetted into a clean plastic cuvette.
• The absorbance of DH5α was 1.800.
• The absorbance of DH10B was 1.82.