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Analysis of caffeine, theobromine and theophylline in coffee by near infrared spectroscopy (NIRS) compared to high-performance liquid chromatography (HPLC) coupled to mass spectrometry
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
ISSN : 0003-2670 CODEN : ACACAM
Analytica chimica acta A. 2005, vol. 538, n° 1-2, pp. 195-203 [9 pages] [bibl. : 36 ref.]
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