Determination of Azo Dyes by Resonance-Enhanced Raman Spectroscopy

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Abstract
An examination of the feasibility of using Raman spectroscopy to determine strongly absorbing solutes has been made, with the use of the azo dyes Eriochrome Blue SE, Eriochrome Black T, and Eriochrome Blue Black B as target compounds. These compounds are representative of the large class of dyes which are not easily determined because of their low volatility. They also are examples of compounds which absorb strongly, causing pronounced nonlinear behavior when attempts are made to use resonance-enhanced bands to improve analytical limits of detection, and which produce intense fluorescence which interferes with Raman bands when the strong 514-nm band of the argon-ion laser is used for excitation. The efficacy of internal standard correction for eliminating the effects of self-reversal and variation in intensity of the exciting beam is demonstrated. Limits of detection for the three compounds listed above are 99 ppb, 340 ppb, and 1.5 ppm, respectively.