Determination of Phenols in Water Using Raman Spectroscopy

The potential of Raman spectroscopy for quantitative analysis of phenols in water solution has been investigated. A group of six compounds—phenol, o-chlorophenol, 2, 4-dichlorophenol, 2, 4, 6-trichlorophenol, 2-chloro-S-methylphenol and 2-chloro-4-nitrophenol—was studied with the use of the 514.5, 488.0, and 457.9 nanometer lines of an argon ion laser. Attention was given to the effects of source intensity, optical alignment, and background fluctuations on quantitative results. It was found that the use of an internal standard with each measurement made a significant improvement in the accuracy and precision of results. Two methods of quantitation, peak area measurement and cross-correlation, were used. Results were somewhat better for cross-correlation, presumably because of more effective exclusion of background interference. Limits of detection were calculated based upon the slope and the standard deviation of the intercept of the standard curve. These varied from the range of 100 ppm to 0.3 ppm, depending on the compound. The most important factor controlling sensitivity is occurrence of resonance enhancement.