Question

Table 2. Variation of absorbances (600 nm) using different concentrations of methylene blue. Concentration / µg/ml Absorbance 0 0 2 0.109 4 0.145 6 0.287 8 0.333 10 0.423 11 0.576 20 0.789 25 0.953 Answer the following questions (each 1 mark): (a) Plot an appropriate calibration graph using Excel; what is the equation of best fit? $y = -0.0351x + 0.0634$ (b) Following on from (a), what is your R$^2$ value? (c) Using your plot from (a), calculate the mean and standard deviation of the unknown methylene blue concentration if replicate absorbance values were 0.555, 0.551 and 0.562. y = 0.0392x + 0.0433 y = 0.3971x - 0.0643 y = -0.0371x - 0.0125 y = 0.0377x - 0.0243 0.9785 0.9952 0.9463 0.9853 0.9241 14.10 $\pm$ 0.15 µg/ml 14.95 $\pm$ 0.35 µg/ml 16.18 $\pm$ 0.03 µg/ml 16.22 $\pm$ 0.11 µg/ml

          Table 2. Variation of absorbances (600 nm) using different concentrations of methylene blue.
Concentration / µg/ml Absorbance
0
0
2
0.109
4
0.145
6
0.287
8
0.333
10
0.423
11
0.576
20
0.789
25
0.953
Answer the following questions (each 1 mark):
(a) Plot an appropriate calibration graph using Excel; what is the equation of best fit? $y = -0.0351x + 0.0634$
(b) Following on from (a), what is your R$^2$ value?
(c) Using your plot from (a), calculate the mean and standard deviation of the unknown methylene blue concentration if replicate
absorbance values were 0.555, 0.551 and 0.562.
y = 0.0392x + 0.0433
y = 0.3971x - 0.0643
y = -0.0371x - 0.0125
y = 0.0377x - 0.0243
0.9785 0.9952 0.9463 0.9853 0.9241
14.10 $\pm$ 0.15 µg/ml 14.95 $\pm$ 0.35 µg/ml 16.18 $\pm$ 0.03 µg/ml 16.22 $\pm$ 0.11 µg/ml

Table 2. Variation of absorbances (600 nm) using different concentrations of methylene blue.
Concentration / µg/ml Absorbance
0
0
2
0.109
4
0.145
6
0.287
8
0.333
10
0.423
11
0.576
20
0.789
25
0.953
Answer the following questions (each 1 mark):
(a) Plot an appropriate calibration graph using Excel; what is the equation of best fit? y = -0.0351x + 0.0634
(b) Following on from (a), what is your R^2 value?
(c) Using your plot from (a), calculate the mean and standard deviation of the unknown methylene blue concentration if replicate
absorbance values were 0.555, 0.551 and 0.562.
y = 0.0392x + 0.0433
y = 0.3971x - 0.0643
y = -0.0371x - 0.0125
y = 0.0377x - 0.0243
0.9785 0.9952 0.9463 0.9853 0.9241
14.10 ± 0.15 µg/ml 14.95 ± 0.35 µg/ml 16.18 ± 0.03 µg/ml 16.22 ± 0.11 µg/ml

Added by Joshua L.

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