1. STEP 1 – DETERMINE THE WAVELENGTH OF LIGHT TO USE
If a solution appears red, it is primarily absorbing its complimentary color, green
EX8-1 (of 8)

2. STEP 1 – DETERMINE THE WAVELENGTH OF LIGHT TO USE
ABSORBANCE SPECTRUM – A graph of the absorbance of a solution at different wavelengths
EX8-2 (of 8)

3. STEP 1 – DETERMINE THE WAVELENGTH OF LIGHT TO USE
WAVELENGTH OF PEAK ABSORBANCE – The wavelength of light most strongly absorbed
EX8-3 (of 8)

4. STEP 2 – PREPARE STANDARD SOLUTIONS
Use a series of Red Dye #40 solutions of known concentrations in order to measure their absorbance's at the peak wavelength to plot absorbance vs. concentration
Absorbance
Concentration of Red Dye #40
EX8-4 (of 8)

5. STEP 2 – PREPARE STANDARD SOLUTIONS
STANDARD SOLUTIONS – Solutions of known concentration
EX8-5 (of 8)

6. STEP 3 – MAKE A CALIBRATION LINE
= mx + b
m (slope) =
b (Y-intercept) =
correlation =
C: g/L g/L g/L g/L g/L A:
y = mx b
= (44.32 L/g)C
m = Δy
____ Δx
= Δ Absorbance
_____________________
Δ Concentration
= no units
____________
g/L
= L/g
EX8-6 (of 8)

7. STEP 4 – MEASURE ABSORBANCE OF YOUR SAMPLE
If your diluted Gatorade sample has an absorbance of 1.352, find its concentration
= mx + b
m (slope) =
b (Y-intercept) =
correlation =
= (44.32 L/g)C
= (44.32 L/g)c
1.352 = (44.32 L/g)c
1.351 = (44.32 L/g)c
= c
____________
44.32 L/g
0.030 g/L = c
EX8-7 (of 8)

8. STEP 4 – MEASURE ABSORBANCE OF YOUR SAMPLE
Calculate the extinction coefficient at this wavelength, with units
A = (44.32 L/g)c
A = ɛ l c + b m
m = ɛ l
m = ɛ
___ b
= L/g
_____________
1.00 cm
= L/gcm
EX8-8 (of 8)