Authors:Aneta Hałka, Paweł Płocharz, Andrzej Torbicz, and Tadeusz Dzido
We have investigated the use of pressurized planar electrochromatography (PPEC) and planar chromatography (TLC) for reversed-phase separation of a mixture of acetylsalicylic acid, caffeine, and acetaminophen. The mixture was separated on C18 plates; the mobile phase was prepared from acetonitrile (ACN), buffer, and bidistilled water. The effects of operating conditions such as mobile phase composition, type of the stationary phase, and mobile phase buffer pH on migration distance, separation selectivity, and separation time in TLC and PPEC were compared. The results showed that pressurized planar electrochromatography of these drugs is characterized by faster separation, better performance, and different separation selectivity. In conclusion, PPEC is a very promising mode for future application in pharmaceutical analysis.
We present a planar chromatographic separation method for the compounds caffeine, artemisinin, and equol, separated on high-performance thin-layer chromatography (HPTLC) silica gel plates. As solvents for separation, methyl t-butyl ether and cyclohexane (1:1, V/V) have been used for equol, cyclohexane and ethyl acetate (7:3, V/V) for artemisinin, and ethyl acetate and acetone (7:3, V/V) for caffeine. After separation, the plate was scanned with a very specific time of flight-direct analysis in real time-mass spectrometry (TOF-DART-MS) system using the (M + 1)+ signals of equol, artemisinin, and caffeine. The (M + 1) peak of artemisinin at 283.13 m/z is clearly detectable, which is the proof that DART-MS is applicable for the quantitative determination of rather instable molecules. The planar set-up of DART source, HPTLC plate and detector inlet in a line showed higher sensitivities compared to desorption at an angle. The optimal detector voltage increases with the molar mass of the analyte, thus an individual determination of optimal detector voltage setting for the different analyte is recommended to achieve the best possible measurement conditions. In conclusion, DART-MS detection in combination with an HPTLC separation allows very specific quantification of all three compounds.
Authors:EH Gilglioni, CM Ghuidotti, VR Vilela, C Bataglini, JP Furlan, JA Berti, MMD Pedrosa, and VAF Godoi
hypoglycemia is common in T1DM on the night following exercise and, as in a vicious cycle, the response to exercise on the following session is impaired ( 10 ).
There are many substances that interfere with the glycemic control, such as caffeine (1
Authors:Lenka Findoráková, Katarína Győryová, Jana Kovářová, V. Balek, F. Nour El-Dien, and L. Halás
Novel zinc(II) complex compounds of general formula Zn(C6H5COO)2·L2 (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour
of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the
anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures.
On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was
found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results
of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.
Caffeine has been found to display a low-temperatureβ- and a high-temperatureα-modification. By quantitative DTA the following data were determined: transformation temperature 141±2°; enthalpy of transition 4.03±0.1 kJ·mole−1; enthalpy of fusion 21.6±0.5 kJ·mole−1; molar heat capacity
in good accord with drop-calorimetric data. For the constants of the equation log (p/Pa)=−A/T+B, static vapour pressure measurements on liquid and solidα-caffeine, and effusion measurements on solidβ-caffeine yielded:
Authors:Anna Gałan, Wioleta Jesionek, Barbara Majer-Dziedzic, Łukasz Lubicki, and Irena Choma
Coffee, due to its common consumption, is one of the main sources of polyphenols in human diet. Coffee species and coffee-related products differ in composition and content of main components, such as chlorogenic acid and caffeine. Chemical and biological fingerprints of various Coffea arabica L. extracts were obtained in order to check and compare their antibacterial and antioxidant properties. The antibacterial activity of green and roasted coffee seeds and pomace was evaluated against Bacillus subtilis using thin-layer chromatography (TLC)-direct bioautography. TLC-2,2-diphenyl-1-picrylhydrazyl (DPPH) test was used to determine antioxidant properties of the afore-mentioned extracts. Furthermore, different solvents and several extraction methods such as simple maceration, maceration under stirring, and ultrasonic accelerated extraction were tested. The most efficient method of extraction of caffeine and chlorogenic acid was chosen based on quantitative TLC analysis. Additionally, these two main components of coffee were quantitatively determined in commercial products of green coffee.