Determination of Caffeine in Beverages by Capillary Zone Electrophoresis: An Experiment for the Undergraduate Analytical Laboratory

Abstract

Certain individuals may be sensitive to specific compounds in comsumer products. It is important to quantify these analytes in food products in order to monitor their intake. Caffeine is one such compound. Determination of caffeine in beverages by spectrophotometric procedures requires an extraction procedure, which can prove time-consuming. Although the corresponding determination by HPLC allows for a direct injection, capillary zone electrophoresis provides several advantages such as extremely low solvent consumption, smaller sample volume requirements, and improved sensitivity.

Analysis of Caffeine in Beverages Using Aspirin as a Fluorescent Chemosensor

“…1 Caffeine is considered harmless for adults (at doses of less than 100 mg/day) but is of concern for young children and pregnant women. 2 Several experiments have been published in this Journal for the analysis of caffeine in coffee, tea, and carbonated beverages using high pressure liquid chromatography, 3−5 thin-layer chromatography, 6,7 capillary electrophoresis, 5,8 solid-phase microextraction, 9 electrospray ionization-mass spectrometry, 10 and gas chromatography/mass spectrometry. 7,9 The amount of caffeine and various phenols in tea leaves and green tea dietary supplements has also been reported.…”

Determination of additives in food by capillary electrophoresis

“…The method was successfully applied to the analysis of black tea and cocoa. Conte and co-workers [64] described a CZE method for the analysis of caffeine using nicotinate as an internal standard. However, as they used a 100 cm column for the separations the analysis time was long, approximately 16 min.…”

“…Using this method to determine caffeine levels in real samples would produce positive error if other neutral components were present as they would migrate unresolved with caffeine. With this in mind, Zhao and Lunte [65] developed a MEKC method using SDS as the micellar phase (see Table 5 for full details) with an analysis time of only two min compared to 14 min and 16 min for the methods described by Vogt and co-workers [63] and Conte and co-workers [64], respectively. To achieve such a rapid analysis time, they used a short column (25 cm to the detector) and avoided the use of an organic modifier.…”

Capillary Zone Electrophoresis for the Analysis of Peptides: Fostering Students’ Problem-Solving and Discovery Learning in an Undergraduate Laboratory Experiment

“…Indeed, CE is routinely used in research applications for the analysis of peptides. − Microfluidic CE devices are often connected to electrospray mass spectrometers for proteomic analysis. − Capillary electrophoresis is covered in most analytical textbooks, and several laboratory experiments have been developed to demonstrate the power of this technique . These include laboratories aimed at determining the amount of caffeine in various foods and beverages, − separation of barbiturates, analysis of cations in soil and water samples, − studying the reaction products from an organic chemistry experiment, , the analysis of various foods and food dyes, and analgesic formulations . Laboratories with biological applications include determining protein amino acid composition, determining the amino acid composition of a dipeptide using the related micellar electrokinetic capillary chromatography technique, carbohydrate analysis, and determining the diffusion constant of dopamine .…”