HPLC determination of caffeine in tea, chocolate products and carbonated beverages

Camargo, Mônica Cristiane Rojo de; Toledo, Maria Cecília de Figueiredo

doi:10.1002/(sici)1097-0010(199910)79:13<1861::aid-jsfa448>3.0.co;2-y

Cited by 25 publications

(19 citation statements)

References 10 publications

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“…Results obtained with the cultivars studied are within the suggested limit for caffeine intake of 400 mg day −1 . However, it is important to emphasise that there are other sources of caffeine in the diet that may contribute to the total intake of this compound, such as soft drinks, tea, chocolate, energy drinks and guarana powder (Camargo & Toledo, ; Camargo et al ., ; Tfouni et al ., ).…”

Section: Resultsmentioning

confidence: 97%

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

Tfouni

Carreiro

Teles

et al. 2013

Int J of Food Sci Tech

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Summary The influence of coffee cultivar, roasting degree and brewing procedure in the presence and transfer of caffeine and caffeoylquinic acids (CQAs) from ground roasted coffee to the brew was evaluated. Two coffee cultivars were roasted in three roasting degrees and brewed using two different procedures. Compounds were determined simultaneously by HPLC‐DAD. Caffeine levels ranged from 87.3 to 122.5 mg/100 mL for Coffea arabica cv. Catuaí Amarelo and from 123.3 to 192.0 mg/100 mL for C. canephora cv. Apoatã. The sum of CQA isomers ranged from 24.2 to 41.3 mg/100 mL for brews prepared with dark roasted coffee and from 187.7 to 295.6 mg/100 mL for light roasted ones. Brews prepared by boiling showed higher content of the compounds than the corresponding filtered ones. C. arabica cv. Catuaí Amarelo light roasted coffee brew presented the lowest caffeine/CQA ratio, regardless of the brewing procedure used, in comparison with the highest ratio of the dark boiled brews.

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Section: Resultsmentioning

confidence: 97%

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

Tfouni

Carreiro

Teles

et al. 2013

Int J of Food Sci Tech

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“…The time required for the body to eliminate one‐half of the total amount of caffeine consumed (the caffeine half‐life) varies from several hours to several days, but for the average nonsmoking adult it is about 3–4 hr (22, 23). Caffeine is present in coffee, tea, soft drinks, cocoa, chocolate, and kola nuts (24). No EKG abnormalities were seen when giving 400 mg of caffeine to normal healthy volunteers (25, 26).…”

Section: Discussionmentioning

confidence: 94%

New algorithm for quantifying vascular changes in dynamic contrast‐enhanced MRI independent of absolute T₁ values

Haacke

Filleti

Gattu

et al. 2007

Magnetic Resonance in Med

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In this work, we present a new method for predicting changes in tumor vascularity using only one flip angle in dynamic contrast-enhanced (DCE) imaging. The usual DCE approach finds the tissue initial T 1 value T 1 (0) prior to injection of a contrast agent. We propose finding changes in the tissue contrast agent uptake characteristics pre-and postdrug treatment by fixing T 1 (0). Using both simulations and imaging pre-and postadministration of caffeine, we find that the relative change (NR50) in the median of the cumulative distribution (R50) is almost independent of T 1 (0). Fixing T 1 (0) leads to a concentration curve c(t) more robust to the presence of noise than calculating T 1 (0). Consequently, the NR50 for the tumor remains roughly the same as the ideal NR50 when T 1 (0) is exactly known. Further, variations in eating habits are shown to create significant changes in the R50 response for both liver and muscle. In conclusion, analyzing data with fixed T 1 (0) leads to a more stable measure of changes in NR50 and does not require knowl- Dynamic contrast-enhanced MRI (DCE-MRI) is a method for imaging the physiology of the microcirculation. A series of recent clinical studies have shown that DCE-MRIbased measures correlate well with tumor angiogenesis. DCE-MRI is performed after the administration of an intravenous contrast agent, gadolinium-DTPA, to noninvasively assess tumor vascular characteristics. Recently, DCE-MRI has been used to assess antiangiogenic cancer drug effectiveness in Phase I pharmaceutical trials (1-3) by acquiring data before and after drug treatment. The contrast enhancement patterns on DCE-MRI are influenced by tumor angiogenesis, as reflected by elevated vascular endothelial growth factor (VEGF) expression. Therefore, they become valuable indicators for assessing tumor angiogenic activity (4,5) and tumor neovascularization in vivo in hepatocellular carcinoma patients (6,7). The use of DCE has been so important that one would be hesitant to continue testing a drug in the absence of any volume or vascular changes appearing in DCE-MRI unless the patients' survival increased (8).Despite its promise, there are problems in the acquisition and processing of DCE data. Repeatability has been a major problem (9 -11). Given the wide clinical use of DCE-MRI, this is an important issue that must be directly addressed. One approach is to improve the methodology itself with more rapid high-resolution respiratory free scanning methods (12). And this will happen with the advent of parallel imaging (13,14). The other is to better process existing data.From our review of many DCE-MRI experiments and projects at the MRI Research facility in the Department of Radiology at Wayne State University, we have found that the causes of most of the DCE errors are related to noise in the T 1 estimates and to physiologic changes in the blood flow (BF) from one day to the next. Normally, an estimate for the baseline T 1 (referred to here as T 1 (0)) is obtained from multiple flip angle (FA) images (15). Any inconsist...

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“…However, it was possible to increase the sensitivity of the method to caffeine by increasing the injection volume, and a 9:1 signal-to-noise ratio was achieved at 0.5 g ml −1 using a 7.5 l injection volume. The measured values of sensitivity were comparable with those reported for caffeine in other complex media [36][37][38]. Table 3 shows correlation coefficient values (r 2 ) of the regression line fitted to the standard curves obtained in each medium, and shows the intra-and inter-day variability.…”

Section: Resultsmentioning

confidence: 99%

A liquid chromatography method for quantifying caffeine dissolution from pharmaceutical formulations into colloidal, fat-rich media

Williams¹,

Ward²,

Hardy³

et al. 2010

Journal of Chromatography B

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HPLC determination of caffeine in tea, chocolate products and carbonated beverages

Cited by 25 publications

References 10 publications

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

New algorithm for quantifying vascular changes in dynamic contrast‐enhanced MRI independent of absolute T₁ values

A liquid chromatography method for quantifying caffeine dissolution from pharmaceutical formulations into colloidal, fat-rich media

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HPLC determination of caffeine in tea, chocolate products and carbonated beverages

Cited by 25 publications

References 10 publications

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

New algorithm for quantifying vascular changes in dynamic contrast‐enhanced MRI independent of absolute T1 values

A liquid chromatography method for quantifying caffeine dissolution from pharmaceutical formulations into colloidal, fat-rich media

Contact Info

Product

Resources

About

New algorithm for quantifying vascular changes in dynamic contrast‐enhanced MRI independent of absolute T₁ values