UV-Visible Spectrophotometric Determination of Phenol in Wastewater-Experiment of Instrumental Analysis

Propose

1.     Learn to use UV-2100 UV-Visible Spectrometer.

2.     Become familiar with the determination of phenol in wastewater.

Principle

Phenol is a chemical substance which is toxic, harmful and unfriendly for the environment. But it is still used in food and drug, so wastewater containing phenol is produced during manufacturing. The most important thing is controlling the concentration of phenol in the wastewater.

    Neutral phenol wastewater has a strong absorption at λ_max = 270 nm. We can utilize the characteristic to determine the concentration of phenol in the wastewater according to Lambert-Beer law.

Equipment

1.     Shimadzu UV-2100 uv-Visible Spectrometer

UV-Visible spectrometer

Deuterium lamp

Tungsten lamp

2.     Volumetric flask 100mL x1, 50mL x6

3.     Quartz cuvettes

Chemicals

1.     Standard phenol solution, 1.000 L, 0.3170 g/L

2.     Wastewater

Procedure

1.     Turn on the spectrometer and allow about 30 minutes for warm up.

2.     Fill the blank cuvette with pure water (reference solution). Polish to clean, insert into the cuvette chamber, aligning mark to front. Close chamber cover. Click the blank icon.

3.     Determine the full spectrum of the standard phenol sample.

4.     Set the wavelength at 270 nm. Dilute following samples into 50.00mL with volumetric flasks.

Label	Volume of Standard Phenol Solution
0	0.00 mL
1	2.00 mL
2	4.00 mL
3	6.00 mL
4	8.00 mL
5	10.00 mL

Label	Volume of Unknown
Unknown	2.00 mL

5.     Measure absorption of samples and make a calibration curve with sample 1 to sample 5.

6.     Determine the concentration of phenol of the unknown with the calibration curve.

Results

1.     The full UV spectrum of standard phenol solution (solvent: water).

  

2.     Calibration Curve of Phenol Solution

Label	Absorption (270.00 nm)	Concentration (mg/L)
0	0.000	0.000
1	0.197	12.680
2	0.387	25.360
3	0.571	38.040
4	0.756	50.720
5	0.948	63.400

Equation	y = a + b*x
Adj. R-Square	0.99986
		Value	Standard Error
Absorption	Intercept	0.005	0.00305
Absorption	Slope	0.01487	7.95E-05

y = 0.005 + 0.01487*x

3.     Determination of the Unknown

Label	Absorption (270.00 nm)
Unknown	0.416

0.416 = 0.005 + 0.01487*x

=> x = 27.640 mg/L

Concentration of Phenol of the Unknown Sample

27.640 mg/L

    So we can get the molar absorptivity

    (0.416 / ((27.640 mg/L) /1000 / (94.11g/mol))) / (1.00 cm)

  = 1416.42 L mol⁻¹ cm⁻¹

Molar absorptivity of Neutral Phenol solution (270.00 nm)

27.640 mg/L