Simultaneous determination of caffeine, theobromine and theophylline in foods and pharmaceutical preparations by using ion chromatography

Fabrication of poly-sulfosalicylic acid film decorated pure carbon fiber as electrochemical sensing platform for detection of theophylline

In this work, we integrated the superiority of good conductivity, large surface area of carbon fibers and the catalytic property, good biocompatibility of polymer sulfosalicylic acid to construct a novel electrochemical sensor to detect theophylline in drug analysis. The morphology of nanocomposite was characterized by scanning electron microscopy (SEM). The polymerization between monomers was observed by Fourier transform infrared spectroscopy (FTIR). The composite between carbon material and polymer was verified by Raman spectrum. Under the optimal experimental conditions, the concentration of theophylline (0.6∼137 μM) and the peak current value revealed a good linear relationship and the limit of detection as low as 0.2 μM. In addition, the proposed sensor exhibits repeatability, stability and ease of selectivity.

A new approach to ion exchange chromatography with conductivity detection for adulterants investigation in dietary supplements

The extent of adulteration of dietary supplements has significantly increased in recent years. This situation worries health authorities and requires auxiliary analytical tools for the investigation of illegal substances purposely added. Ion exchange chromatography with conductivity detection is a consolidated analytical technique for the determination of inorganic compounds in various matrices. This technique has been applied to the pharmaceutical characterization of mainly impurities and degradation products. This work presents a new approach to ion exchange chromatography as a screening method to investigate the presence of amfepramone, femproporex, sibutramine, bisacodyl and amiloride in dietary supplements advertised for weight loss. The method was optimized and validated using a Metrosep C4 100/4.0 cation exchange column. The mobile phase consisted of 1.8 mm HNO₃ containing 2% acetonitrile (v/v), with a flow rate of 0.9 ml min^-1 , and nonsuppressed conductivity detection was applied. The limits of detection and quantification varied from 1.01 to 3.62 mg L^-1 and from 1.48 to 8.72 mg L^-1 , respectively. The proposed method was successful applied to 78 solid dietary supplement samples, in two of which adulterations were found. Moreover, ion exchange chromatography with conductivity detection could be easily used for quality control without prior complex sample pre-treatment.

A high performance liquid chromatography method for simultaneous detection of 20 bioactive components in tea extracts

Tea is the second most widely consumed beverage and contains various bioactive compounds. A simple method to analyze these compounds is of great scientific and commercial interest. In this work, a 30 min HPLC method was developed using a simple gradient elution system, and the mobile phases and elution gradients were optimized. This method separated 17 polyphenols and three alkaloid compounds in tea extracts, including catechins, alkaloids, phenolic acids, flavonols, and flavone, which are responsible for the bioactivity and flavor of tea. Excellent linearity was observed for all standard calibration curves, and correlation coefficients were above 0.9994. Heatmap analysis demonstrated significant separation between green, black, and pu-erh tea samples. The method described here is accurate and sensitive enough for the determination of active components in tea and could potentially be applied to other food products for the comprehensive investigation of their quality.

Simultaneous determination of ascorbic acid and caffeine in commercial soft drinks using reversed-phase ultraperformance liquid chromatography

A new reversed-phase ultraperformance liquid chromatography method with a photodiode array detector was developed for the quantification of ascorbic acid (AA) and caffeine (CAF) in 11 different commercial drinks consisting of one energy drink and 10 ice tea drinks. Separation of the analyzed AA and CAF with an internal standard, caffeic acid, was performed on a Waters BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm i.d.), using a mobile phase consisting of acetonitrile and 0.2M H₃PO₄ (11:89, v/v) with a flow rate of 0.25 mL/min and an injection volume of 1.0 μL. Calibration graphs for AA and CAF were computed from the peak area ratio of AA/internal standard and CAF/internal standard detected at 244.0 nm and 273.6 nm, respectively. The developed reversed-phase ultraperformance liquid chromatography method was validated by analyzing standard addition samples. The proposed reversed-phase ultraperformance liquid chromatography method gave us successful results for the quantitative analysis of commercial drinks containing AA and CAF substances.

A rapid and simple determination of caffeine in teas, coffees and eight beverages

Caffeine was extracted and preconcentrated by the simple, fast and green method of dispersive liquid-liquid microextraction (DLLME) and analysed by gas chromatography-nitrogen phosphorus detection (GC-NPD). The influence of main parameters affecting the extraction efficiency investigated and optimised. Under the optimal conditions, the method was successfully applied to determination of caffeine in different real samples including five types of tea (green, black, white, oolong teas and tea bag), two kinds of coffee (Nescafe coffee and coffee), and eight beverages (regular Coca Cola, Coca Cola zero, regular Pepsi, Pepsi max, Sprite, 7up, Red Bull and Hype).The limit of detection (LOD) and limit of quantification (LOQ) were 0.02 and 0.05 μg mL(-1), respectively. Linear dynamic range (LDR) was 0.05-500 μg mL(-1) and determination coefficient (R(2)) was 0.9990. The relative standard deviation (RSD) was 3.2% (n=5, C=1 μg mL(-1)).

Determination of the caffeine contents of various food items within the Austrian market and validation of a caffeine assessment tool (CAT)

The caffeine content of 124 products, including coffee, coffee-based beverages, energy drinks, tea, colas, yoghurt and chocolate, were determined using RP-HPLC with UV detection after solid-phase extraction. Highest concentrations of caffeine were found for coffee prepared from pads (755 mg l⁻¹) and regular filtered coffee (659 mg l⁻¹). The total caffeine content of coffee and chocolate-based beverages was between 15 mg l⁻¹ in chocolate milk and 448 mg l⁻¹ in canned ice coffee. For energy drinks the caffeine content varied in a range from 266 to 340 mg l⁻¹. Caffeine concentrations in tea and ice teas were between 13 and 183 mg l⁻¹. Coffee-flavoured yoghurts ranged from 33 to 48 mg kg⁻¹. The caffeine concentration in chocolate and chocolate bars was between 17 mg kg⁻¹ in whole milk chocolate and 551 mg kg⁻¹ in a chocolate with coffee filling. A caffeine assessment tool was developed and validated by a 3-day dietary record (r²= 0.817, p < 0.01) using these analytical data and caffeine saliva concentrations (r²= 0.427, p < 0.01).

Rapid determination of caffeine in one drop of beverages and foods using drop-to-drop solvent microextraction with gas chromatography/mass spectrometry

A simple and rapid sample cleanup and preconcentration method for the quantitative determination of caffeine in one drop of beverages and foods by gas chromatography/mass spectrometry (GC/MS) has been proposed using drop-to-drop solvent microextraction (DDSME). The best optimum experimental conditions for DDSME were: chloroform as the extraction solvent, 5 min extraction time, 0.5 microL exposure volume of the extraction phase and no salt addition at room temperature. The optimized methodology exhibited good linearity between 0.05 and 5.0 microg/mL with correlation coefficient of 0.980. The relative standard deviation (RSD) and limits of detection (LOD) of the DDSME/GC/MS method were 4.4% and 4.0 ng/mL, respectively. Relative recovery of caffeine in beverages and foods were found to be 96.6-101%, which showing good reliability of this method. This DDSME excludes the major disadvantages of conventional method of caffeine extraction, like large amount of organic solvent and sample consumption and long sample pre-treatment process. So, this approach proves that the DDSME/GC/MS technique can be applied as a simple, fast and feasible diagnosis tool for environmental, food and biological application for extremely small amount of real sample analysis.

Survey of caffeine levels in retail beverages in Portugal

The caffeine content of 85 retail beverage samples purchased from local supermarkets between 1995 and 2004 was determined. The potential intake of caffeine through the consumption of these beverages (but excluding coffee) was estimated for students of the University of Coimbra, Portugal. The caffeine content of the beverages ranged from 47.5 to 282.5 mg l(-1) for teas, from 20.1 to 47.2 mg l(-1) for tea extracts samples, and from 80.7 to 168.7 mg l(-1) for cola soft drinks. Caffeine was not completely absent from caffeine-free colas, and energy drinks had a far greater caffeine content than regular drinks, ranging from 21 to 2175 mg l(-1). Soft drinks were consumed by 72% of the individuals, although 14% of the survey participants did not drink any of the different types of the beverages studied. Contrary to expectations for this age group, no consumptions of energy drinks was reported. Daily caffeine intake was estimated to range from 4.7 to 200 mg day(-1), but with only 5% reporting a daily intake around 200 mg caffeine. Cola-type beverages were an important dietary source of caffeine for the population studied. Statistical differences in the caffeine intake between the male and female populations were found, with p = 0.014, being higher for the male population. Of the beverages studied, cola-type drinks showed statistical differences for the male population, p = 0.03, and tea showed statistical differences for female population p = 0.013, respectively.

PLE in the analysis of plant compounds

Pressurised liquid extraction (PLE) is recognised as one of the most effective sample preparation methods. Despite the enhanced extraction power of PLE, the full recovery of an analyte from plant material may require multiple extractions of the same sample. The presented investigations show the possibility of estimating the true concentration value of an analyte in plant material employing one-cycle PLE in which plant samples of different weight are used. The performed experiments show a linear dependence between the reciprocal value of the analyte amount (E*), extracted in single-step PLE from a plant matrix, and the ratio of plant material mass to extrahent volume (m(p)/V(s)). Hence, time-consuming multi-step PLE can be replaced by a few single-step PLEs performed at different (m(p)/V(s)) ratios. The concentrations of rutin in Sambucus nigra L. and caffeine in tea and coffee estimated by means of the tested procedure are almost the same as their concentrations estimated by multiple PLE.

PLE in the analysis of plant compounds

A broad spectrum of sample preparation methods is currently used for the isolation of pharmacologically active compounds from plant and herbal materials. The paper compares the effectiveness of infusion, microwave assisted solvent extraction (MASE), matrix solid-phase dispersion (MSPD) and pressurised liquid extraction (PLE) as sample preparation methods for the isolation of caffeine from green tea leaves. The effect of PLE variables, such as extraction temperature, pressure and time, on the yield of caffeine from the investigated matrix is discussed. The obtained results revealed that PLE, in comparison with other sample preparation methods applied, has significantly lower efficacy for caffeine isolation from green tea leaves. The evaluation of PLE conditions leads to the conclusion that elevated pressure applied in the PLE process is the factor hindering the extraction.

Solid-phase ultraviolet sensing system for determination of methylxanthines

In this study the use of a single continuous-flow solid-phase UV spectrophotometric sensing system for determination of methylxanthines was evaluated. Two methods were developed to determine caffeine (CF) and theophylline (TP) in pharmaceuticals and CF and theobromine (TB) in food and beverages. The sensor is based on transient and sequential retention of the analytes on a hydrophobic sensing solid zone (octadecyl silane C18 gel) and detection of their intrinsic UV absorbance. Temporary sequencing of the arrival of the analytes at the sensing zone is achieved by on-line separation of one of the analytes using a pre-column of the same particulate material, placed just before the flow cell. After TB or TP had been carried toward the sensing zone (by the appropriate carrier solution), produced its transitory signal, and been eluted by the carrier, an appropriate eluting solution (25% MeOH) was used to elute CF, which was strongly retained on the minicolumn, so that its transient signal could be recorded. The sensing zone was completely regenerated with this eluting solution, and so was ready for analysis of another sample. After selecting the most suitable conditions, the sensing system was calibrated in the range 1-16 and 1-12 mg L(-1) for CF and TP-TB, respectively, giving detection limits below 0.1 mg L(-1) with RSD values less than 3%. The usefulness of this approach has been evaluated by applying it to the determination of caffeine, theobromine, and theophylline in different samples of food, beverages, and pharmaceutical formulations. The results were in satisfactory agreement with those obtained by use of an HPLC reference method.

Simultaneous determination of theophylline and caffeine by proton magnetic resonance spectroscopy using partial least squares regression techniques

A 1H-NMR procedure based on an analysis of its data by a multivariate calibration method was conducted for the simultaneous determination of theophylline and caffeine in synthetic and real samples. Partial least squares regression (PLS) was chosen as the calibration method. The methyl signals of theophilline at 3.36 and 3.54 ppm that overlapped with those of caffeine were significant characteristics which were employed in this study for their analyses. The proposed method was successfully applied to recovery studies of theophylline and caffeine from real tablet samples.

Simultaneous determination of artificial sweeteners, preservatives, caffeine, theobromine and theophylline in food and pharmaceutical preparations by ion chromatography

A novel ion chromatographic method was proposed for the simultaneous determination of artificial sweeteners (sodium saccharin, aspartame, acesulfame-K), preservatives (benzoic acid, sorbic acid), caffeine, theobromine and theophylline. The separation was performed on an anion-exchange analytical column operated at 40 degrees C within 45 min by an isocratic elution with 5 mM aqueous NaH2PO4 (pH 8.20) solution containing 4% (v/v) acetonitrile as eluent, and the determination by wavelength-switching ultraviolet absorbance detection. The detection limits (signal-to-noise ratio 3:1) for all analytes were below the sub-microg/ml level. Under the experimental conditions, several organic acids, including citric acid, malic acid, tartaric acid and ascorbic acid, did not interfere with the determination. The method has been successfully applied to the analysis of various food and pharmaceutical preparations, and the average recoveries for real samples ranged from 85 to 104%. The levels of all analytes determined by this method were in good agreement with those obtained by the high-performance liquid chromatographic procedure. The results also indicated that ion chromatography would be possibly a beneficial alternative to conventional high-performance liquid chromatography for the separation and determination of these compounds.

Analysis of tea components by high-performance liquid chromatography and high-performance capillary electrophoresis

Tea is one of the most popular beverages in the world. The number of reports on the analysis of tea components, especially for catechins, has recently been increasing. We review the recent reports on the analysis of tea components using the analytical methods of high-performance liquid chromatography and high-performance capillary electrophoresis.