Development of a sequential injection system for the assessment of potassium and color in alcoholic beverages

  • Maria João Morais Nunes (Student)

Student thesis: Master's Thesis


In the last centuries, beverages derived from alcoholic fermentation, namely beer and wine, have been of great importance, given the increasing rate of consumption, resulting in a need for large-scale production. Thus, it becomes essential to develop methodologies capable of measuring more than one parameter simultaneously, to facilitate the work of quality monitoring in line production. In this work, a biparametric system was developed for the determination of potassium content and color in wines and beers. Thus, several method development and optimization processes were carried out throughout the study. The final assembly of the sequential analysis system (SIA) consists of a 10-port selection valve connected to the different solutions and detectors used. In one port was placed the connection to the sample/standard, in another port the connection to the potentiometer, for the potentiometric determination of potassium, and in another port the connection to the spectrophotometer, for the determination of color. To facilitate the switch of sample/standard there was also a port with a connection to a waste, where the excess was discarded. The developed method allowed the determination of potassium between the concentrations of 1.08 x 10-1 M and 1.08 x 10-3 M, with detection and quantification limits of 3.90 x 10-5 M and 1.62 x 10-4 M, respectively. This system also allowed the color determination for each sample. For the potassium determination, the values obtained by the potentiometric system were compared with the values obtained by flame emission photometry, and there was no statistically significant difference (<10%). The potassium calibration curve proved to be stable over time (monthly), as the respective calibration curves were found to be identical within statistical variation. The methodology for determining color was validated by comparing the results with the reference method. It is concluded that the system can be applied to beer and wine samples in an industrial context with the aim of facilitating simultaneous measurements of the two parameters, using less volume and with less operator work, making it easier to perform other tasks.
Date of Award25 Mar 2022
Original languageEnglish
Awarding Institution
  • Universidade Católica Portuguesa
SupervisorAntónio O. S. S. Rangel (Supervisor) & Raquel Mesquita (Co-Supervisor)


  • sequential analysis system (SIA)
  • Potassium
  • Color
  • Wine
  • Beer


  • Mestrado em Biotecnologia e Inovação

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