University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Beverage -> non alcoholic -> coffee

Citations 3

"Flow Injection Fourier Transform Infrared Determination Of Caffeine In Coffee"
Vib. Spectrosc. 1999 Volume 21, Issue 1-2 Pages 143-150
Zouhair Bouhsain, Jose M. Garrigues, Salvador Garrigues and Miguel de la Guardia

Abstract: A fully automatized procedure has been developed for the Fourier transform infrared (FT-IR) spectroscopic determination of caffeine in coffee samples. The method involves the online extraction of caffeine with CHCl3. Samples, weighed inside empty PTFE cartridges of 0.5 cm internal diameter (i.d.) and 1.5 mL volume, were humidified with four drops of 0.25 M NH3. The cartridge was installed in a flow manifold, in which samples were extracted in a closed-flow system with 1 mL CHCl3, during 6 min. Four hundred microliters of the extract were introduced in a microflow cell and absorbance measured as a function of time at 1659 cm-1, with a baseline established between 1900 and 830 cm-1, thus providing a fiagram. Peak height values of the Fl recordings, obtained for samples, were interpolated in an external calibration line established from standard solutions of caffeine in CHCl3,. The method provided a limit of detection (LOD) of 9 mg L-1 caffeine, a relative standard deviation of 0.6% for five independent measurements of a solution containing 1 mg mL-1 and a sampling frequency of the whole procedure of 6 h-1. Results obtained for market samples agree well with those found by the official chromatographic-spectrometric method, but involving a drastic reduction of solvents, from the 200 mL ether and 50 mL CHCl3, required for each sample preparation by the reference procedure to less than 30 mL CHCl3, necessaries for the whole determination of caffeine in a sample, also including standards and carrier solution.
Caffeine Spectrophotometry Interface Optimization Method comparison

"Coupled Flow Injection Analysis - Flame-atomic Absorption Spectrometry For The Quantitative Determination Of Aluminum In Beverages And Waters Incorporating Online Cation-exchange"
Anal. Chim. Acta 1992 Volume 269, Issue 1 Pages 1-7
Henryk J. Salacinski, Philip G. Riby, Stephen J. Haswell*

Abstract: Tea leaf samples (0.5 g) were digested at 85°C for 45 min in a mixture of HNO3 (4 ml) and HClO4 (1 ml) and diluted to 10 mL with 5% HNO3. Samples of tea and coffee infusions and water were acidified with 5% HNO3. These samples (250 µL) were injected via a loop into a SCX preparative column (500 mg) with water as the carrier, followed by elution with 4 M HCl (250 µL) directly into the nebulizer of a flame AAS for the determination of Al. The AAS and nebulizer were optimized for max. absorbance prior to the determination and the peristaltic pump of the flow system set to give an equivalent delivery. Rectilinear calibrations were obtained from 0.07 to 6.45 µg mL-1 of Al from various timed depositions with a coefficient of variation of 1.1% and a detection limit of 75 ng mL-1. A method for determining the aluminum levels in local water, tea leaf digest, tea and coffee infusions by means of online cation exchange flow injection - flame atomic absorption spectrometry (FIA-FAAS) is described. Quant. results can be carried out down to 75 ng mL-1 of Al using sample volumes in the range 6.0-24.0 mL. The method using a conventional FAAS system was found to be rapid, simple and relatively inexpensive offering good selectivity and typical relative standard deviation of 1-2% (n=10) with a relative error of about 2%.
Aluminum Ion exchange Sample preparation Sample preparation Spectrophotometry Nebulizer Column

"Determination Of Acidity Of Coffee By Flow Injection Analysis With Electrochemical Detection"
J. Agric. Food Chem. 1997 Volume 45, Issue 6 Pages 2124-2127
Tetsuo Fuse, Fumiyo Kusu, and Kiyoko Takamura

Abstract: The present study was conducted to establish a sensitive, rapid, reliable, and accurate method for determining the acidity of coffee by flow injection analysis (FIA) using an electrochemical detector with a glassy carbon electrode and a carrier solution of ethanol containing 38 mM LiClO4 and 3 mM 2-methyl-1,4-naphthoquinone (vitamin K3, VK3). FIA signals for 21 coffee samples showed good correlation with titratable acidity, a common chemical measure of the sourness of coffee. FIA signals were also related with sourness intensity determined by sensory panel test. Change in the acidity of coffee, due to roasting of coffee beans, was monitored by FIA. The present method was found adequate for determining coffee acidity.
Acidity Amperometry Electrode Method comparison