Calibration Curve
A major US corporation recently developed methodology to measure weight fractions of one of their co-polymer lines using LC retention times (mobile phase solubility was based upon relative fractions of copolymers).  The table below provides the results of the calibration that was done for this polymer characterization.
LC RT
Wt Fract.
16
0.0
25.5
0.15
27.5
0.17
31.5
0.25
33.2
0.27
36.0
0.35
39.0
0.41
45.7
0.62
1.  Develop a second order equation for this using retention time as the independent variable (x) and weight fraction as the dependent variable (y).  Use the developed formula to predict the retention time for a 50-50 Polymer mixture having a weight fraction of 0.50.  Plot the calibration curve developed along with the individual points using the format discussed in class.

 
 

Standard Addition Problem
Fluoride Ion Selective Electrode (ISE) quantification of fluoride samples was done using standard addition with the following results:
 

mgF-
added 
Response
0.0
100.0
90.0.0
143.3
180.0
184.8
270.0
224.0
360.0
269.1
2.  Determine the mass of fluoride ion in the sample.  Clearly show all equations and all work.  Include a graphical display of the data to include showing the appropriate X-intercept.

 
 
 
 

Internal Standard Problem:

3.  A solution containing 0.0837 M analyte (X) and 0.0666 M standard (S) gave peak areas of Ax=423 and As=347 (areas in arbitrary units).  To determine an unknown concentration of the analyte (X), 10.0 mL of 0.0146 M standard (S) was added to 10.0 mL of the unknown solution then the mixture was diluted to 25.0 mL in a volumetric flask. Analysis of this mixture resulted in peak areas of Ax=553 and As=582.
a.  Calculate the response factor, F; clearly write the formula you are using on this sheet.
b.  Calculate the concentration of the analyte in the diluted solution; once again show the formula being used.
c.  Calculate the concentration for the analyte in the original unknown solution prior to dilution.