A New Procedure for Caffeine Determination

Abstract

The content of caffeine in multicomponent natural objects (tea leaves, coffee beans, and instant coffee) and caffeine-containing beverage foods was determined by ion-exchange chromatography.Since caffeine is an inherent component of some plants and foodstuffs produced from them [1], availability of the reliable procedures of its determination is important for various-purpose analyses (such as technological, umpire, etc.). In accordance with GOST (State Standard) [2], the main method of caffeine analysis is a photometric determination based on hydrolytic oxidation of caffeine into tetramethylpurpuric acid followed by photometric registration of the absorption density at l 540 nm. The main disadvantage of this procedure is underestimation of the caffeine content in the samples [1].The most general procedure of caffeine determination used in laboratories beyond Russia is reversedphase high-performance liquid chromatography (RP HPLC). Kusch and Knupp [3] compared the analytical data on the content of caffeine in beverage foods determined by high-performance thin-layer chromatography and RP HPLC. They found that, despite some restrictions, each procedure provides reliable results with small measurement errors. As for caffeine determination in vegetable extracts of tea and coffee, the problem is more complex. The content of caffeine in tea and coffee is so high that no additional procedures of its preconcentration (such as solid-phase extraction often used in the analysis of caffeine in biological liquids [4]) are required. With solid-phase extraction and RP HPLC, the detection limit of the caffeine in protein-containing samples was determined as 200 ng cm 33 . However, wide assortment of compounds extracted with water from tea and coffee hinders direct determination of caffeine by RP HPLC, which is probably due to the short retention times of the polar caffeine molecules, especially in sorbents with small and intermediate content of grafted hydrocarbon chains. As a result, the caffeine peaks overlap with peaks of concomitant compounds even in the case of gradient elution. Another technique recently tested for determination is capillary electrophoresis [5]. Though this method provides very high separation efficiency, it is not widely used yet.Nishitani and Sagesaka [6] performed an HPLC analysis of green tea components (catechins, phenolic glycosides, acids, and caffeine) on a C18 Wakosil-II 5C18 HG (3 0 150 mm) reversed-phase column (Wako Pure Chemical Industries, Ltd., Japan) using complex gradient profile with changes in the flow rate. The analysis time was 40 min. Smaller amount of components (8) can be separated with this system in 20 min. The detection limit of the components varied from 1.4 to 3.5 ng and the concentration dependence was linear up to charges of 1500 ng; the introduced/found ratio was 96 3103%.In this study we used a procedure more selective to caffeine, based on two separation mechanisms through ion-exchange and hydrophobic interactions. EXPERIMENTALAnalysis was performed on an FPLC liquid chroma...

Rapid and Sensitive Determination of Methylxanthines in Commercial Brands of Tea Using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry

“…A variety of analytical techniques and sample preparation procedures have been developed and registered for determination and separation of these three methylxanthines in plants, environmental samples, drugs, food, and biological fluids. These proposed methods include UV-Vis spectrophotometry [22–24], thin-layer chromatography (TLC) [25], ion chromatography (IC) [26], FT-Raman spectrometry [27], IR spectrometry [28], capillary electrophoresis (CE) [29, 30], NMR spectroscopy [31], mass spectroscopy [32], gas chromatography-mass spectrometry (GC-MS) [15], high-performance thin-layer chromatography (HPTLC) [33, 34], voltammetry [35, 36], and high-performance liquid chromatography (HPLC) which was reported as the most frequently used approach [1, 2, 10, 37–49].…”

Simultaneous HPLC Determination of Caffeine, Theobromine, and Theophylline in Food, Drinks, and Herbal Products

“…The most popular techniques for the determination of CF in different mixtures, especially in the recent reports, consist of high-performance liquid chromatography (HPLC) and its variants (1)(2)(3)(4)(5)(6)(7)(8)(9). Other methods include batch UV-vis spectrophotometry (10,11), thin-layer chromatography and its variants (1,(12)(13)(14), ion chromatography (15), Fourier transform-Raman spectrometry (16), Fourier transform-infrared spectrophotometry (17), etc.…”

Structure-Bioactivity Relationships of Methylxanthines: Trying to Make Sense of All the Promises and the Drawbacks

“…After the pre-treatment and extraction steps, a wide range of analytical techniques have been used for the analysis and quantification of the main methylxanthines including capillary gas chromatography (GC) [81], gas chromatography-mass spectrometry (GC-MS) [82,83], spectrophotometry [77,84,85,86], Fourier transform-Raman spectrometry [87], spectrofluorimetry [88,89], Fourier transform-infrared spectrophotometry [90], capillary electrophoresis (CE) [91,92,93] and micellar electrokinetic electrophoresis (MEKC) [94,95,96], voltammetry [97,98], radioimmunoassay (RIA) [99,100], thin-layer chromatography (TLC) [68,101,102] ion-exchange chromatography [103] and even solid-phase ultraviolet sensing [104]. Supercritical fluid extraction, specifically using supercritical carbon dioxide and ethanol, has been proved to be an effective method for methylxanthine analysis from a number of different samples/sources (guaraná seeds, maté leaves, and cocoa beans) [73].…”