Thermal Infrared Enthalpimetry in Paper Microzone Plates for Green and High Throughput Determination of Wine Acidities

Abstract

The use of paper devices in chemical analysis has been increased due to their low cost, high surface area, portability, and biodegradability. A novel use of paper devices is proposed using thermal infrared enthalpimetry (TIE) for a rapid, green, and high throughput determination of wine acidities. The determination of total, fixed, and volatile acidities in red, white, and sparkling wine was carried out, and the results were compared with AOAC titration method. A multichannel pipette was used for reagent addition and an infrared camera for the temperature monitoring. The pipetting and temperature measurement conditions presented direct influence in the deviations among the measurements. The results obtained by TIE presented an agreement between 96 and 104% with the reference method (AOAC 962.12), for all samples. A high sample throughput was achieved reaching 480 samples h-1 for total acidity. A significant reduction in sample volume and reagent consumption was also obtained, with energy consumption up to 60 times lower in relation to the AOAC method. The association of TIE with a paper device provided a rapid, reliable and green method for the determination of acidities of wines.

Combining In-Tip Reaction and Infrared Thermal Imaging for Fast and Portable Enthalpimetric Analysis

“…The solutions were homogenized under magnetic stirring, and the difference in temperature was related to the limiting reagent (the analyte). This proposed method, called thermal infrared enthalpimetry (TIE), has been successfully used for the analysis of food and drugs in a high throughput and also greener way. − In general, polymeric microplates are used, but recently, some improvements were proposed to reduce the volume of solutions as the reaction in paper microzone plates. , However, the proposed setup used for TIE presented some limitations for field analyses (e.g., the need for stirring) and several parameters (e.g., the total volume of solutions, pipette dispensing rate, and stirring speed) should be adjusted to reach suitable measurements …”

“…11−15 In general, polymeric microplates are used, but recently, some improvements were proposed to reduce the volume of solutions as the reaction in paper microzone plates. 16,17 However, the proposed setup used for TIE presented some limitations for field analyses (e.g., the need for stirring) and several parameters (e.g., the total volume of solutions, pipette dispensing rate, and stirring speed) should be adjusted to reach suitable measurements. 12 In the proposed work, a novel approach is proposed to perform enthalpimetric analysis directly in the pipette tips and make TIE even more portable and straightforward for analysis.…”