User:Monika Gasiorek/Notebook/CHEM-571 2014F/2014/10/21

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October 21, 2014

Primary Experiment #1 - KI Titrations

500 mL of 10 mM NH4SCN was prepared using a volumetric flask.

  • 0.3882 g of solid NH4SCN was dissolved in 500 mL of water

NH4SCN Standardization

3 mL of 1 M HCl, 2 mL of AgNO3, and 10 mL of water were titrated with the prepared NH4 solution in the presence of 400 μL of ferric alum indicator.

  • Volume required to reach equivalence point: 15.60 mL

AgNO3+NH4SCN→AgSCN(s)+NH4NO3

  • Reaction is 1:1
  • 0.63788g AgNO3/50mL = 0.0127576 g/mL *2 mL *1mole/169.86 g = 0.000150204 mol AgNO3 = mol Ag = mol SCN = mole NH4SCN
  • 0.000150204 mol NH4SCN/0.0156 L

[NH4SCN]=9.63 mM

KI Titrations

The standardized NH4SCN titrant was used to titrate 500 μL* samples of each of the dialysis wells from Primary Experiment #1. The same procedure was followed as was done for KI standardization on October 8, 2014, with the exception of KI sample size (500 μL instead of 1 mL). Additionally, 400 μL of indicator were used instead of 200 μL.

KI Titrations.png

*NOTE: The 50 mM KI titration was initially done incorrectly and the remainder of the sample was used for trial 2. There were only 350 μL left at this point.

NOTE: These values are inconsistent with both the starting conditions and expected results. Each sample will be re-tested for KI concentration using the Iodide Ion Selective Electrode currently being assembled/tested.

Primary Experiment #2 - Work-Up

Fluorescence/UV Analysis Fluorescence was run on DI water and 30:1 [Au]:[Protein] colloid to determine if fluorescence was necessary for the colloid vs. CaCl2 dialysis samples. As demonstrated below, no fluorescence was detected for the colloid (after determining no protein was present in the cuvette with blank water samples), so no fluorescence or UV-VIS analysis was necessary for these samples.

30to1 Colloid Pure Emission Spectrum.png

Ca2+ ISE

Calcium ISE was run on all ten dialysis samples. The samples were transferred to vials that the probe could be placed in. The results are below:

Concentration Colloid Solution Potential Soak Solution Potential
50 mM 77.3 mV 83.6 mV
5 mM 59.9 mV 56.0 mV
0.5 mM 44.7 mV 43.1 mV
50 µM 38.7 mV 34.0 mV
5 µM 35.1 mV 33.2 mV

Iodide Ion Selective Electrode Preparation

Three solutions were prepared:

  1. 10 mL 3 M NaCl
  2. 50 mL 4 M KNO3
  3. 50 mL 0.01 M KI, 0.1 M KNO3

This will be continued tomorrow.