Phenol standard curve by UV-1200 ultraviolet spectrophotometry - Database & Sql Blog Articles

Phenol Standard Curve Using Ultraviolet Spectrophotometry

Key words: ultraviolet spectrophotometry; standard curve preparation; analytical instrument; UV-1300; UV-1500. I. Experimental Objective 1. Understand the basic principles of UV spectroscopy for qualitative and quantitative analysis. 2. Learn how to operate a UV-visible spectrophotometer effectively. II. Experimental Principle Organic compounds containing benzene rings or conjugated double bonds exhibit characteristic absorption in the ultraviolet region. The maximum absorption wavelength (λmax), molar absorptivity (ε), and the shape of the absorption curve are essential for substance identification. Since absorbance (A) is highest at λmax, this wavelength offers the best sensitivity for concentration measurements. In this experiment, we analyze the absorption spectrum of a phenol aqueous solution using a UV spectrophotometer to determine λmax and quantify the sample accordingly. For low or high concentration samples, the transmittance reading can be adjusted by a factor of 10 for better accuracy. This method follows Lambert-Beer’s Law: A = εbc. III. Main Instruments and Reagents Instruments: UV-1300 and UV-1500 UV-visible spectrophotometers; 1 cm quartz cuvettes (2 pieces); 50 mL colorimetric tubes (5 pieces); 5 mL pipettes (1 piece). Reagents: Phenol standard solution (100 mg/L). IV. Experimental Procedure (1) Preparation of Analytical Solutions: Take five 50 mL colorimetric tubes and accurately add 0.5 mL, 1.0 mL, 1.5 mL, 2.0 mL, and 2.5 mL of the 100 mg/L phenol standard solution using a pipette. Dilute each with deionized water to the 25 mL mark and shake well. Record the data in a standard table. (2) Determination of Maximum Absorption Wavelength: Prepare a phenol solution with a concentration of 8 mg/L. Use a 1 cm quartz cuvette and deionized water as the reference solution. Scan the absorption spectrum between 200 nm and 330 nm on the UV-Vis spectrophotometer. Identify λmax1 and λmax2 from the curve. (3) Preparation of the Standard Curve: Measure the absorbance of each phenol solution at the selected λmax, starting from the lowest to the highest concentration. Plot the absorbance versus concentration to create a standard working curve. V. Data Recording and Result Analysis The standard curve is an essential tool for quantitative analysis. By comparing the absorbance of unknown samples to the curve, accurate concentrations can be determined. This method ensures reliable results when following proper experimental procedures and maintaining instrument calibration. Keywords: ultraviolet spectrophotometry; standard curve drawing; analytical instrument; UV-1300; UV-1500