Rapid microplate, green method for high-throughput evaluation of vinegar acidity using thermal infrared enthalpimetry

• Thermal infrared enthalpimetry is a new and promising alternative to titration.
• Sample preparation and determination steps could be performed in the same vessel.
• Sample throughput could be improved by one order of magnitude.
• Analytical operations could be simplified being more suitable for routine analysis.
• Green analytical chemistry principles could be spread by using the proposed method.

Infrared thermal imaging was combined with disposable microplates to perform enthalpimetric analysis using an infrared camera to monitor temperature without contact. The proposed thermal infrared enthalpimetry (TIE) method was used to determine the total, fixed and volatile acidities of vinegars. Sample preparation and analysis were performed in the same vessel, avoiding excessive sample handling and reducing energy expenditure by more than ten times. The results agreed with those of the conventional method for different kinds of vinegars, with values of 1.7%, and 2.3% for repeatability and intermediate precision, respectively. A linear calibration curve was obtained from 0.040 to 1.30 mol L−1. The proposed method provided rapid results (within 10 s) for four samples simultaneously, a sample throughput of up to 480 samples per hour. In addition, the method complies with at least eight of twelve recommendations for green analytical chemistry, making TIE a promising tool for routine vinegar analysis.