Determination of phenol by UV-1100 ultraviolet spectrophotometry - Master's thesis - Dissertation

Determination of Phenol Using Ultraviolet Spectrophotometry

The UV spectrophotometric method is widely used for the determination of phenol in various samples. This experiment aims to understand the principles of ultraviolet spectrophotometry and apply it to quantify phenol in an unknown solution. Objective: - Learn the basic theory of UV spectroscopy for qualitative and quantitative analysis. - Gain hands-on experience with the UV1500 UV-visible spectrophotometer. Principle: Phenol contains a benzene ring with three characteristic absorption bands due to π→π* transitions. The presence of the hydroxyl (-OH) group causes a red shift in the absorption peak, lowering the energy of the π* orbital. By measuring the absorbance at the maximum wavelength (λ_max), we can determine the concentration using the Beer-Lambert law: A = εcl. Materials and Equipment: - Instruments: UV1500 spectrophotometer, 2 cm quartz cuvette, 25 mL colorimetric tubes, 10 mL, 5 mL, 1 mL pipettes, 100 mL and 250 mL beakers, wash bottles. - Reagents: 0.0003 mol/L phenol solution, 1 g/L phenol standard solution prepared by dissolving 1.000 g of phenol in deionized water and diluting to 1 L. A 100 mg/mL solution was obtained by diluting 10 mL of the 1 g/L solution to 100 mL. Procedure: 1. Prepare a standard curve by taking 5 different volumes (1.0, 2.0, 3.0, 4.0, 5.0 mL) of 100 mg/L phenol into 25 mL colorimetric tubes, diluting each to the mark with deionized water. Measure the absorbance at λ_max using a 1 cm quartz cuvette and deionized water as the reference. Plot the absorbance vs. concentration. 2. For the unknown sample, take 10 mL of the solution, dilute to 25 mL, measure its absorbance, and use the standard curve to find the concentration. Data and Results: The calculated concentration of the sample was found to be 20.488 mg/L. After accounting for the dilution factor (2.5), the final concentration is 51.220 mg/L. Keywords: UV spectrophotometry, phenol, spectrophotometer, analytical chemistry.