title: Rapid analysis of caffeine in various coffee samples employing direct analysis in real-time ionization-high-resolution mass spectrometry.
abstract: The development and use of a fast method employing a direct analysis in real time (DART) ion source coupled to high-resolution time-of-flight mass spectrometry (TOFMS) for the quantitative analysis of caffeine in various coffee samples has been demonstrated in this study. A simple sample extraction procedure employing hot water was followed by direct, high-throughput (<1 min per run) examination of the extracts spread on a glass rod under optimized conditions of ambient mass spectrometry, without any prior chromatographic separation. For quantification of caffeine using DART-TOFMS, an external calibration was used. Isotopically labeled caffeine was used to compensate for the variations of the ion intensities of caffeine signal. Recoveries of the DART-TOFMS method were 97% for instant coffee at the spiking levels of 20 and 60 mg/g, respectively, while for roasted ground coffee, the obtained values were 106% and 107% at the spiking levels of 10 and 30 mg/g, respectively. The repeatability of the whole analytical procedure (expressed as relative standard deviation, RSD, %) was <5% for all tested spiking levels and matrices. Since the linearity range of the method was relatively narrow (two orders of magnitude), an optimization of sample dilution prior the DART-TOFMS measurement to avoid saturation of the detector was needed.
authors.affiliation: Faculty of Food and Biochemical Technology, Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic.
authors.forename: Hana
authors.initials: H
authors.lastname: Danhelova
authors.forename: Jaromir
authors.initials: J
authors.lastname: Hradecky
authors.forename: Sarka
authors.initials: S
authors.lastname: Prinosilova
authors.forename: Tomas
authors.initials: T
authors.lastname: Cajka
authors.forename: Katerina
authors.initials: K
authors.lastname: Riddellova
authors.forename: Lukas
authors.initials: L
authors.lastname: Vaclavik
authors.forename: Jana
authors.initials: J
authors.lastname: Hajslova
mesh_terms: D002110:Caffeine / Q000032:analysis*; D003069:Coffee / Q000737:chemistry*; D005504:Food Analysis / Q000379:methods; D013058:Mass Spectrometry; D013997:Time Factors
chemical_list: D003069:Coffee; D002110:Caffeine