Spectrophotometric determination of trace water in organic solvents with a near infrared absorbing dye.

A spectrophotometric method for the determination of trace water in organic solvents using a near infrared absorbing dye has been developed. This method is based on the effect that a minor change in polarity of the solvent caused by trace water content determines the extent of aggregation of a near-infrared dye monomer. This change can be detected spectrophotometrically. The calibration curves for methanol, ethanol, and isopropanol were determined. This method has the highest sensitivity (em = 16.73 unit) for water in isopropanol and the lowest sensitivity (em = 2.806 unit) for water in methanol. The correlation coefficient (R)(2) values for the regression lines ranges from 0.990-0.998. The linear range of the method for ethanol is 0.001-0.5%, for isopropanol is 0.001-0.1%, and for methanol is 0.001-1.0%. The limit of detection for ethanol, isopropanol, and methanol are 0.0001, 0.0001, and 0.005% water, respectively. The developed method is sensitive, simple and easy to operate, and the cost of analysis is low.