Question

Fluoride ion selective electrodes obey the following equation:

      E(V) = K - β(0.0592)log[F^-]

where the fluoride concentration is expressed as mol/L and the temperature coefficient β is normally equal to 1.

In a normal calibration procedure you dilute a standard fluoride solution to between 10 and 20 mg/L fluoride ion and then measure the response of the electrode. You then plot the data and do a linear regression to obtain the fitting coefficients K and β. Use the plotting and linear regression tools in Excel to calculate K and β from the data in the table. The coefficient β is close to 1, and can be determined from a calibration curve.

Data:

F- concentration (mg/L)	E(V)
10.0	-0.358
12.0	-0.362
14.0	-0.366
16.0	-0.369
18.0	-0.372
20.0	-0.375

We are asked to find the value for K and beta.

For K, I got 0.949

For beta, I got -0.542

However, both values were wrong. I appreciate any help and/or explanation!

Answer 1