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A quantitative method for the determination of caffeine, formic acid, trigonelline and 5-(hydroxymethyl)furfural (5-HMF) in soluble coffees by applying the proton nuclear magnetic resonance technique ( 1 H NMR) is proposed. Each of these compounds records a singlet signal at the 7.6–9.5ppm interval of the spectrum, and its area is used to determine the concentration. 3-(Trimethylsilyl)-2,2,3,3-tetradeuteropropionic...
A quantitative determination method of formic acid in apple juices is proposed by means of the proton nuclear magnetic resonance ( 1 H NMR) technique. Formic acid gives a singlet signal at the 8.2–8.4ppm interval of the spectrum, and its area is used to determine the concentration of the acid. 1,3,5-Benzenetricarboxylic acid is added to the juice as an internal standard. Since the chemical...
1 H NMR spectroscopy was applied to the quantitative determination of malic and citric acids in apple, apricot, pear, kiwi, orange, strawberry and pineapple juices. Aspartic acid was studied as a potential interference. The effect of the sample pH on the chemical shifts of signals from malic, citric and aspartic acids was examined and a value of 1.0 was selected to carry out the determination...
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