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Monday, October 7, 2013

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 λmax = 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



3 comments:

  1. Replies
    1. No problem
      Just enjoy the science~

      Delete
  2. Hello, when you indicate to determine the full spectrum of the standard phenol sample you mean to measure the absorption at all wavelenghts? When you talk about the standard phenol sample it has a concentration of 1000 mg/L thanks!!

    ReplyDelete