Sequential Injection Analysis of Free and Total Potassium in Wines Using Potentiometric Detection and Microwave Digestion

Abstract

An automatic procedure for the determination of free and total potassium in wines is described that combines sequential injection analysis with potentiometric detection. A sequential injection mounting is coupled to a microwave system to conduct the on-line digestion of the sample, thereby making the injection of samples possible without prior treatment. Free potassium was determined by injecting 110 µL of sample and forwarding it to the detection system. In the evaluation of total potassium, the sample was previously digested with 390 µL of hydrogen peroxide for 60 seconds at 700 W in a microwave oven. Using an optimized mounting, 10 samples of different wine types were analyzed (white, red, and port), and results were then compared with those provided by flame emission photometry. Relative standard deviations obtained were always below 3% and sampling rate attained was about 14 samples per hour.