Automated Multicomponent Analysis of Soft Drinks Using 1D 1H and 2D 1H-1H J-resolved NMR Spectroscopy

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is evaluated as an efficient analytical technique for simultaneous identification and quantitation of multiple compounds in alcohol-free beverages. The method was validated for three different types of soft drinks, including a beverage with high sugar content, a diet product and an energy drink. The sample preparation required only 600 μL of degassed soft drink, 70 μL of 0.1 % TSP-d4 in D2O (for referencing and locking) and 100 μL of phosphate buffer (pH = 2.89). The simultaneous quantitative analysis of eleven compounds, such as sugars, flavourings, sweeteners, organic acids, alcohol (ethanol), vitamins and amino acids, was achieved using an automated procedure based on the PULCON principle (pulse length based concentration determination). Recovery rates were between 80 % (HMF) and 106 % (ethanol). The limits of quantitation (LOQ) varied between 52 mg/L for saccharin and 12 g/L for sucrose due to different matrix contents. Sample analysis time is about 25 min including sample preparation and automated data processing. A comparison with conventional methods showed the suitability of NMR for routine analysis of soft drinks.