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Pure Appl. Chem., 2012, Vol. 84, No. 10, pp. 2015-2025

Published online 2012-09-24

Reagent-free analytical flow methods for the soft drink industry: Efforts for environmentally friendly chemical analysis

Thitirat Mantim1,2, Phoonthawee Saetear1,2, Saowapak Teerasong3,2, Sumonmarn Chan-Eam1,2, Kamonthip Sereenonchai4,2, Natchanon Amornthammarong2,5, Nuanlaor Ratanawimarnwong6,2, Prapin Wilairat1,2,7, Wanchai Meesiri8, Kanchana Uraisin1,2 and Duangjai Nacapricha1,2*

1 Center of Excellence for Innovation in Chemistry and Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok, Thailand
2 Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs.), Thailand
3 Department of Chemistry, Faculty of Science, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, Thailand
4 Department of Chemistry, Faculty of Science and Technology, Thammasat University, Pathumthani, Thailand
5 National Oceanic and Atmospheric Administration (NOAA), Ocean Chemistry Division/AOML, Miami, FL, USA
6 Department of Chemistry, Faculty of Science, Srinakharinwirot University, Bangkok, Thailand
7 National Doping Control Center, Mahidol University, Bangkok Thailand
8 Bangkok High Lab Co., Ltd., Bangkok, Thailand

Abstract: The evolution of an entirely green analytical system for industrial quality control of carbonated drinks is described. The developed flow system is capable of providing analytical data of the dissolved CO2, sucrose, and color of a sample consecutively in real-time. The system has been carefully designed on the basis of “reagent-free”, meaning that no added chemicals are required for the analysis. The system first vaporizes CO2 from the soft drink in a gas–liquid separation chamber, with a channel for a flow of pure water as the CO2 acceptor. The dissolved CO2 alters the conductivity of the water stream, which is directly related to the concentration of CO2 in the soft drink. The sucrose content is measured based on the “schlieren effect”, the sample plug flows out of the vaporization chamber into a colorimeter with a near-infrared/light-emitting diode (NIR/LED) as light source. The schlieren effect arises at the boundary of pure water and soft drink with refraction of light in proportion to the sugar concentration. The system also measures the absorbance of the sample using an RGB-LED. The related principles and preliminary experiments as proof of concept are described as well as the construction of the flow system for this completely reagent-free analyzer. A simple flow injection system using the schlieren effect was also developed for rapid quantitative analysis of sugar in noncarbonated soft drinks.