User:Moira M. Esson/Notebook/CHEM-571/2013/09/04

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Objectives

  • Perform error analysis on the compiled data calibration curve.
    • Determine the standard deviation for the data points.
    • Determine the confidence interval for 90% and 95% confidence.
    • Determine if any data can be ruled out using a Q-test.
  • Determine the molar extinction coefficient for both adenosine and inosine.
  • Determine the concentration of an unknown adenosine sample(taken from Javier's group).
  • Perform Grubb's test on outlying peak of adenosine molar extinction coefficent graph.
  • Perform data analysis on molar extinction coefficient graphs(both adenosine and inosine).


Group calibration curve data

Figure 1. CHEM-571 Calibration Curve for Adenosine
Image:Chem571groupadenosinecalibration09082013.png

  • The Grubb's test will be employed to determine whether the points that lie outside of the line of best fit are outliers


Figure 2. CHEM-571 Calibration Curve for Inosine
Image:Chem571inosinecalibrationcurve09082013.png
Table 1. Molar absorptivity for Adenosine at a wavelength of 259nm and Inosine at a wavelength of 249nm

Molar Absorptivity(Lmol-1cm-1) '
Adenosine14025
Inosine11007


Matt Hartings What wavelength does this molar absorptivity correspond to?

Table 2. Standard deviation of Inosine Absorbance values

Comcentration(M) Standard Deviation
4.80E-050.10707708
4.00E-050.12254917
3.20E-050.0943149
2.40E-050.06671357
1.60E-050.04841797
8.00E-060.04748368


Table 3. Standard deviation of Adenosine Absorbance values

Concentration(M) Standard Deviation
3.00E-050.072537576
2.50E-050.045680412
2.00E-050.064123319
1.50E-050.056753854
1.00E-050.0313289
5.00E-060.046559639


Table 4. 95% Confidence Intervals for Adenosine Absorbance values

Concentration(M) Confidence Interval
3.00E-050.063580821
2.50E-050.04003991
2.00E-050.056205534
1.50E-050.049746033
1.00E-050.027460487
5.00E-060.040810573


Table 5. 90% Confidence Intervals for Adenosine Absorbance Values

Concentration(M) Confidence Interval
3.00E-050.053358707
2.50E-050.033602552
2.00E-050.047169171
1.50E-050.041748187
1.00E-050.023045567
5.00E-060.034249313


Table 6. 95% Confidence Intervals for Inosine Absorbance Values

Concentration(M) Confidence Interval
4.80E-050.093855474
4.00E-050.10741711
3.20E-050.082669136
2.40E-050.058475948
1.60E-050.042439442
8.00E-060.041620516


Table 7. 90% Confidence Intervals for Inosine Absorbance Values

Concentration(M) Confidence Interval
4.80E-050.078765997
4.00E-050.09014728
3.20E-050.069378126
2.40E-050.049074562
1.60E-050.035616303
8.00E-060.034929038


Table 8. Q-test at 90% confidence for Inosine Absorbance Values

Comcentration(M) Qexp values Suspected outlier(Abs)
4.80E-050.4356060610.331
4.00E-050.6057692310.189
3.20E-050.8806584360.171
2.40E-050.9878048780.128
1.60E-050.4758064520.089
8.00E-060.5348837210.004


  • Note: With 5 data points Qc=0.64. As such, data points 0.171 and 0.128 can be discarded with 90% confidence


Table 9. Q-test at 90% confidence for Adenosine Absorbance Values

Concentration(M) Suspected Outliers(Abs) Qexp
3.00E-050.5580.794444444
2.50E-050.4420.705357143
2.00E-050.4060.8625
1.50E-050.3040.675496689
1.00E-050.1950.5
5.00E-060.1360.405405405


  • Note: With 5 data points Qc=0.64. As such, data points 0.558, 0.442, 0.406, and 0.304 can be discarded with 90% certainty.


Table 10. Grubb's Test for Adenosine Absorbance Values


Concentration(M) Suspected Outliers(Abs) Gexp
3.00E-050.5581.753573888
2.50E-050.4421.725028241
2.00E-050.4061.75599146
1.50E-050.3041.481520326
1.00E-050.1951.532131655
5.00E-060.1361.426127891


  • Note: With 5 data points at a 95% confidence level Gc=1.67. As such, absorbance values 0.558, 0.442 and 0.406 can be discarded with 95% confidence.

Unknown Adenosine Solution

Figure 3. Absorption Spectrum of Unknown Concentration
Image:Unknownadenosine09042013zem.png

  • Using the molar extinction coefficient determined from the calibration curve above the concentration of the unknown is 4.7344E-5 M.
  • Based on the calibration curve, the average error in this calculation is 1%, shown in Table 11(shown below).


Table 11. Calculations relating to the uncertainty in the unknown concentration

Absorbance Concentration (M) Std. dev. Error(%) Average Std.dev Average Error(%)
0.43083.07166E-050.1855621762.3506088610.0789421751
0.36322.58966E-050.1318954291.670785353
0.29342.09198E-050.0860712851.090308
0.2091.4902E-050.0436747710.553250165
0.1471.04813E-050.0216059190.273692974
0.06964.96257E-060.0048434690.061354647

Matt Hartings Based on your calibration curve, what is the error in this measurement?


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