Caffeine analysis

Coc,papaverine, Various drugs yohimbine,heroin, strychnine,caffeine Analysis papaverine in blood Micropak CN-10 300x4 Hexane-CH-ClACN-propy1ami ne (50 25 25 0.l) 57... 

TABLE 5. Caffeine Analysis - Effect of Altitude and Latitude... 

Meinhart AD, Bizzotto CS, Ballus CA, Prado MA, Bruns RE, Filho JT, Godoy HT (2010) Optimisation of a CE method for caffeine analysis in decaffeinated coffee. Food Chem 120 1155-1161. doi 10.1016/j.foodchem.2009.11.048... 

The analysis of APC tablets (a mixture of aspirin, phenacetin, and caffeine) has been a common undergraduate laboratory experiment. This experiment describes modifications to the standard analysis for APC tablets in which paracetamol (also known as acetaminophen) replaces phenacetin. 

Examples of the application of HPLC to the analysis of (a) acetaminophen, salicylic acid, and caffeine (b) chlorinated pesticides (c) tricyclic antidepressants and (d) peptides. (Chromatograms courtesy of Alltech Associates, Inc. Deerfield, IL). 

Caffeine in coffee, tea, and soda is determined by a solid-phase microextraction using an uncoated silica fiber, followed by a GC analysis using a capillary SPB-5 column with an MS detector. Standard solutions are spiked with G3 caffeine as an internal standard. 

This experiment describes a quantitative analysis for caffeine, theobromine, and theophylline in tea, pain killers, and cocoa. Separations are accomplished by MEKC using a pH 8.25 borate-phosphate buffer with added SDS. A UV detector set to 214 nm is used to record the electropherogram. An internal standard of phenobarbital is included for quantitative work. 

Pentoxifylline is stmcturaHy related to other methylxanthine derivatives such as caffeine [58-02-2] (1,3,7-trimethylxanthine), theobromine [83-67-0] (3,7-dimethylxanthine), and theophylline [58-55-9] (3,7-dihydro-1,3-dimethyl-1 H-piirine-2,6-dione or 1,3-dimethylxanthine), which also show radioprotective activity in some instances, suggesting that methylxanthines as a dmg class may radioprotect through a common mechanism (see Alkaloids). In a retrospective analysis of cervical and endometrial cancer patients receiving primary or adjuvant XRT, no association between caffeine consumption and incidence of acute radiation effects has been found. However, there was a decreased incidence of severe late radiation injury in cervical cancer patients who consumed higher levels of caffeine at the time of thek XRT (121). The observed lack of correlation between caffeine consumption and acute radiation effects is consistent with laboratory investigations using pentoxifylline. 

Caffeine, 131 ( arbamide, 126 Carbamine reaction, 71 Carbolic acid, 179 Carbon, qualitative analysis t Carbon, quantitative analysis 4 Carlus method, 22, 28 Chaiitiway s Xi QX o 174 Chloracetic acid, S7 Chloral, 99 Chloral hydrade, 99 ( hlorbydrin, tii / Chlorobenzoic acid, 166 < hlorofonTi, 70 / Chlorutulueiie, 16 ... 

High performance liquid chromatography is used for the separation and quantitative analysis of a wide variety of mixtures, especially those in which the components are insufficiently volatile and/or thermally stable to be separated by gas chromatography. This is illustrated by the following method which may be used for the quantitative determination of aspirin and caffeine in the common analgesic tablets, using phenacetin as internal standard where APC tablets are available the phenacetin can also be determined by this procedure. 

The dense fluid that exists above the critical temperature and pressure of a substance is called a supercritical fluid. It may be so dense that, although it is formally a gas, it is as dense as a liquid phase and can act as a solvent for liquids and solids. Supercritical carbon dioxide, for instance, can dissolve organic compounds. It is used to remove caffeine from coffee beans, to separate drugs from biological fluids for later analysis, and to extract perfumes from flowers and phytochemicals from herbs. The use of supercritical carbon dioxide avoids contamination with potentially harmful solvents and allows rapid extraction on account of the high mobility of the molecules through the fluid. Supercritical hydrocarbons are used to dissolve coal and separate it from ash, and they have been proposed for extracting oil from oil-rich tar sands. 

A sample thought to be caffeine, the stimulant found in coffee, tea, and cola beverages, gave the following elemental analysis 49.5 % C 5.2%H 28.8%N 16.5 % O Does this elemental... 

Begin by calculating the mass of one mole of caffeine (because the percentage analysis is reported to only three significant figures, we need the molar mass to no more than two decimals) ... 

Within the precision of the measured elemental analysis, the experimental percentages are the same as those expected for Cg Hig N4 O2. Thus, the data are consistent with caffeine. 

If the molar mass of the compound is not known, the best we can do is to find the simplest formula that agrees with the elemental analysis. This simplest formula, or empirical formula, contains the smallest set of whole-number subscripts that match the elemental analysis. The empirical formula of caffeine is C4 H5 N2 O. 

GOTO T, YOSHIDA Y, Kiso M and NAGASHIMA H (1996) Simultaneous analysis of individual catechins and caffeine in green tea , J Chromatogr A, 749, 295-9. 

WORTH c c, wiESSLER M and SCHMITZ o J (2000) Analysis of catechins and caffeine in tea extracts by micellar electrokinetic chromatography . Electrophoresis, 21 (17), 3634-... 

The analysis of the methylxanthines (caffeine, theobromine, and theophylline) is important in the areas of nutrition and clinical chemistry. These three compounds compose the majority of the alkaloids present in coffee, tea, cocoa, cola nuts, and guarana. 

GC has seen wide use in food analysis but has not seen a large following in the determination of the nonvolatile alkaloids in foods when compared to HPLC. The 13th edition of the AO AC Methods of Analysis22 lists a GC method for the determination of caffeine in coffee or tea using a thermionic KCI detector with a glass column 6 ft x 4 mm i.d. packed with 10% DC-200 on 80 to 100-mesh Gas Chrom Q. 

Capillary GC was used to obtain high resolution profiles of 27 organic acids, caffeine, and sucrose in dimethylsulphoxide extracts of roast and ground coffees in a 60-min analysis.26 A shortened procedure is also reported for quantitative detection of 5-caffeoylquinic (5-CQA) and quinic (QA) acids and sucrose ng detection limits were achieved. Major commer-... 

HPLC allows a quantitative determination with relatively simple extractions. In many cases, extraction only involves a heating of the commodity with water, followed by filtration and injection onto an HPLC column. In the determination of caffeine, theobromine, and theophylline in cocoa, coffee, or tea, as well as in other foods, there is scarcely a month that passes without a new paper on this assay. Kreiser and Martin provide typical conditions for analysis.28 In their studies, samples were extracted in boiling water and filtered prior to injection onto the HPLC column. The HPLC conditions used a Bondapak reversed phase column and a mobile phase of water methanol acetic acid (74 25 1) with detection at 280 nm. This method is accurate, precise, and conserves time. It has also been adopted by the AOAC as an official method for the determination of theobromine and caffeine in cocoa beans and chocolate products.29... 

This chapter describes use of solid-surface room temperature phosphorimetry (SSRTP) as a detection technique in the liquid chromatographic (LC) analysis of caffeine, theophylline, and theobromine. Measurements were made in a continuous mode, using a 2-nebulizer automatic system for SSRTP analysis (previously optimized for LC detection). Use of SSRTP and UV absorption detection was compared under identical experimental conditions.38... 

Application of HPLC-MS to the analysis of a black tea liquor was studied in a paper by Bailey 39 a great deal of useful information could be obtained without sample pretreatment. A tea liquor was applied to a wide-pore HPLC column connected to a mass spectrometer by a VG Plasmaspray interface. Pseudo-molecular ions were obtained from the flavanols, flavanol gallates, chlorogenic acids, 4-coumarylquinic acids, and caffeine, but the flavanol glycosides were extensively fragmented by the interface. Fragments were obtained from unresolved polymer that supported its previous designation as a flavanol polymer. 

Hurst, W.J. and Martin, R.A. Jr, The quantitative determination of caffeine in beverages using capillary electrophoresis analysis, 21,389-91,1993. 

Chocolate milk samples prepared from sweetened cocoa powders averaged 58 mg per serving of theobromine and 5 mg per serving of caffeine.28 Analysis of a "home-style" recipe resulted in higher methylxanthine values — 94 mg theobromine and 10 mg caffeine per serving. However, the authors noted that this recipe also had a stronger chocolate flavor. The lower values reported by Zoumas et al. and Blauch and Tarka compared to others was attributed to the inability of older methods to separate theobromine and caffeine, and the lack of precision and accuracy of the older methods. A compendium of theobromine and caffeine values reported for chocolate beverages from both published and unpublished studies has been compiled in Table 8. 

It is necessary to determine the methylxanthine content of chocolate foods, as well as beverages, in order to obtain an accurate assessment of the total amount of theobromine and caffeine that is ingested via the diet. This area of analysis has received little attention, and only scant published data exist on the methylxanthine content of chocolate foods. 

Baer, R., Effects of caffeine on classroom behavior, sustained attention, and a memory task in preschool childern. Journal of Applied Behavior Analysis 20(3), 225-234, 1987. 

Stein, M., Krasowski, M. Leventhal, B., Phillips, W. and Bender, B., Behavioral and cognitive effects of methylxanthines A meta-analysis of theophyliine and caffeine. Arch Pediatr Adolesc Med 150(3), 284-288, 1996. 

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