ChE 408 – Engineering Experimental Design
In-Class Project
Calibration Curve for Spectrophotometric Determination of Crystal Violet Dye Concentration
Here
is a page from a laboratory notebook.
Measurements were made to develop a calibration curve so that the
concentration (in moles per liter) of an aqueous dye solution may be determined
by measuring the UV absorbance of the solution. Using the data provided, develop an equation that will allow
someone to calculate the concentration of a CVD solution given its
absorbance. Evaluate the validity of
your equation. Then determine the
concentrations of solutions whose absorbances are 0.5, 1.0, and 1.5. (For now, use the confidence limits on the
adjustable parameters to estimate the uncertainty in the concentration. Later in the course, we will learn a more
correct way to estimate the uncertainty on values predicted using a regression
model.)
Laboratory Notebook
Calibration data for aqueous crystal violet dye (CVD), UV absorbance at 492 nm.
Absorbance = -log10(light transmitted / incident light); 100 % light transmitted gives an absorbance of zero.
0.3479 ± 0.0010 g CVD (formula weight 408 g/mole) placed in 1 L volumetric flask; diluted with water to 1000 ± 1 ml.
Diluted measured volume of CVD stock solution with water in volumetric flask. Placed resulting dilute solution in UV cuvette and measured absorbance at 492 nm.
|
Run # |
CVD stock solution added ml |
Total solution volume ml |
Absorbance |
|
1 |
0 |
|
0.00021 |
|
2 |
8.5 ± 0.1 |
1000 ± 1 |
0.65731 |
|
3 |
Repeat of run #2 |
|
0.6635 |
|
4 |
8.5 ± 0.1 |
1000 ± 1 |
0.62227 |
|
5 |
10.0 ± 0.1 |
1000 ± 1 |
0.7552 |
|
6 |
25.0 ± 0.1 |
1000 ± 1 |
1.84568 |
|
7 |
10.0 ± 0.1 |
500 ± 1 |
1.43606 |
|
8 |
Repeat of run #5 |
|
0.74222 |
|
9 |
Repeat of run #2 |
|
0.62371 |
|
10 |
13.5 ± 0.5 |
500 ± 1 |
1.93544 |
|
11 |
15.0 ± 0.5 |
1000 ± 1 |
1.07576 |
|
12 |
5.9 ± 0.2 |
1000 ± 1 |
.41681 |