Spectrophotometric flow-injection method for determination of sorbic acid in wines

A simple, rapid, and accurate spectrophotometric flow-injection method was developed for the determination of sorbic acid in wines based on the oxidation of sorbic acid with K₂Cr₂O₇/H₂SO₄ at 100°C, followed by reaction of the resulting malonaldehyde with thiobarbituric acid, also at 100°C, to give a red product, the absorbance of which is measured at 532 nm. The method requires no prior distillation of the wine and allows a sampling rate of 40 per hour. The calibration graph was linear from 0 to at least 15 μg mL⁻¹ (the linear correlation coefficient was 0.9997), and the detection limit (signal-to-noise ratio, 3) was 0.14 μg mL⁻¹. The relative standard deviation of ten replicate determinations was 1.58%. The method was applied successfully to the determination of sorbic acid in red and white wines. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 299–303, 1999