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Titre du document / Document title

Analysis of caffeine, theobromine and theophylline in coffee by near infrared spectroscopy (NIRS) compared to high-performance liquid chromatography (HPLC) coupled to mass spectrometry

Auteur(s) / Author(s)

HUCK C. W. (1) ; GUGGENBICHLER W. (1) ; BONN G. K. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, Jnnrain 52a, 6020-Innsbruck, AUTRICHE

Résumé / Abstract

Coffee is one of the most important raw materials within the international trade, for which highest quality is demanded. Due to the high number of samples to be analysed, new analytical techniques providing fast and reliable data about the quality are essential. Therefore, we established a new analytical method based on near infrared spectroscopy (NIRS) for the quantitation of the three main alkaloids caffeine (Caf), theobromine (Tbr) and theophylline (Tph) in roasted coffee after discrimination of the rough green beans into Arabic and Robusta. This validated method was compared to the most commonly used liquid chromatography (LC) connected to UV and mass spectrometric (MS) detection. In this course non-porous silica-C18 showed to enable the analysis of the three alkaloids with high robustness within ∼2.5 min, compared to 20 min employing porous silica-C18 as a stationary phase. As analysis time plays an important role in choosing a reference method for the calibration of the NIR-spectrometer, the non-porous silica-C18 phase offers a very fast method. Coupling of the optimised LC method to a mass spectrometer (MS) via an electrospray ionisation (ESI) interface not only allowed to identify Caf, Tbr and Tph by their characteristic fragmentation pattern using collisionally induced dissociation (CID), but also to quantitate the content of the three analytes, which was found to be 6% higher compared to UV-detection. The validated LC-UV method was chosen as a reference method for the calibration of the NIRS system. Analysis of 83 liquid coffee extracts in random order resulted for Caf and Tbr in values for S.E.E. (standard error of estimation) of 0.34, 0.40 g/100g, S.E.P. (standard error of prediction) of 0.07 and 0.10 g/100 g with correlation coefficients of 0.86 and 0.85 in a concentration range between 0.10 and 4.13 g/100 g. Compared to LC the lower limit of detection (LOD) of the NIRS-method is found at 0.05 g/100 g compared to 0.244-0.60 ng/100 g in LC, which makes it impossible to analyse Tph by NIRS. Therefore, main focus is put on the NIRS analysis of caffeine and theobromine. Nevertheless, NIRS offers a serious alternative to LC for the coffee producing industry because of the short analysis time of a few seconds and a guaranteed high sample throughput.

Revue / Journal Title

Analytica chimica acta    ISSN  0003-2670   CODEN ACACAM 

Source / Source

2005, vol. 538, no1-2, pp. 195-203 [9 page(s) (article)] (36 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Amsterdam, PAYS-BAS  (1947) (Revue)

Mots-clés anglais / English Keywords

Theobromine

;

Chemical ionization

;

Calibration

;

Stationary phase

;

Robustness

;

Silica

;

Ultraviolet spectrometry

;

Alkaloid

;

Quantitative analysis

;

Chemical analysis

;

Raw materials

;

Mass spectrometry

;

HPLC chromatography

;

Near infrared spectrometry

;

Coffee

;

Theophylline

;

Caffeine

;

Mots-clés français / French Keywords

Théobromine

;

Ionisation chimique

;

Etalonnage

;

Phase stationnaire

;

Robustesse

;

Silice

;

Spectrométrie UV

;

Alcaloïde

;

Analyse quantitative

;

Analyse chimique

;

Matière première

;

Spectrométrie masse

;

Chromatographie HPLC

;

Spectrométrie IR proche

;

Café

;

Théophylline

;

Caféine

;

Mots-clés espagnols / Spanish Keywords

Ionización química

;

Contraste

;

Fase estacionaria

;

Robustez

;

Sílice

;

Espectrometría UV

;

Alcaloide

;

Análisis cuantitativo

;

Análisis químico

;

Materia prima

;

Espectrometría masa

;

Cromatografía HPLC

;

Espectrometría IR próximo

;

Café

;

Teofilina

;

Cafeína

;

Mots-clés d'auteur / Author Keywords

Coffee

;

Caffeine

;

Theobromine

;

Theophylline

;

Liquid chromatography

;

Electrospray ionisation mass spectrometry

;

Near infrared spectroscopy

;

Localisation / Location

INIST-CNRS, Cote INIST : 3950, 35400012559689.0250

Nº notice refdoc (ud4) : 16721109



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