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Publications (53) View all
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Article: Reliable Peak Selection for Multisample Analysis with Comprehensive Two-Dimensional Chromatography.
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ABSTRACT: Comprehensive two-dimensional chromatography is a powerful technology for analyzing the patterns of constituent compounds in complex samples, but matching chromatographic features for comparative analysis across large sample sets is difficult. Various methods have been described for pairwise peak matching between two chromatograms, but the peaks indicated by these pairwise matches commonly are incomplete or inconsistent across many chromatograms. This paper describes a new, automated method for post-processing the results of pairwise peak matching to address incomplete and inconsistent peak matches and thereby select chromatographic peaks that reliably correspond across many chromatograms. Reliably corresponding peaks can be used both for directly comparing relative compositions across large numbers of samples and for aligning chromatographic data for comprehensive comparative analyses. To select reliable features for a set of chromatograms, the Consistent Cliques Method (CCM) represents all peaks from all chromatograms and all pairwise peak matches in a graph, finds the maximal cliques, and then combines cliques with shared peaks to extract reliable features. The parameters of CCM are the minimum number of chromatograms with complete pairwise peak matches and the desired number of reliable peaks. A particular threshold for the minimum number of chromatograms with complete pairwise matches ensures that there are no conflicts among the pairwise matches for reliable peaks. Experimental results with samples of complex bio-oils analyzed by comprehensive two-dimensional gas chromatography (GCxGC) coupled with mass spectrometry (GCxGC-MS) indicate that CCM provides a good foundation for comparative analysis of complex chemical mixtures.Analytical Chemistry 04/2013; · 5.86 Impact Factor -
Article: Non-separative headspace solid phase microextraction-mass spectrometry profile as a marker to monitor coffee roasting degree.
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ABSTRACT: This study describes a non-separative Headspace-Solid-Phase-Microextraction-Mass-Spectrometry (HS-SPME-MS) approach, in view of its application to on-line monitoring of a roasting process. The system can quickly provide representative and diagnostic fingerprints of the volatile fraction of samples and, in combination with appropriate chemometric pattern-recognition and regression techniques, can successfully be applied to characterize, discriminate and/or correlate patterns with the roasting process. Eighty coffee samples of different varieties, geographical origins and blends were analyzed. The experimental HS-SPME-MS results show that the TIC fingerprint can be used to discriminate the degree of roasting; diagnostic ion abundance(s) or ratios were closely correlated with the roasting process; both could successfully be used as markers or Analytical Decision Makers, to monitor roasting processes on-line, and to define quality and safety of roasted coffee.Journal of Agricultural and Food Chemistry 10/2012; · 2.82 Impact Factor -
Article: A Further Tool To Monitor Coffee Roasting Process: Aroma Composition And Chemical Indices.
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ABSTRACT: Coffee quality is strictly related to its flavour and aroma developed during the roasting process, that, in their turn, depend on variety and origin as well as time, temperature and degree of roast. This study investigates the possibility to combine chemical (aroma components) and physical (color) parameters through chemometric approaches to monitor roasting process, degree of roast and aroma formation by analyzing a suitable number of coffee samples from different varieties and blends. In particular, a correlation between the aroma composition of roasted coffee obtained by HS-SPME-GC-MS and degree of roast, defined by the color, has been searched. The results showed that aroma components are linearly correlated to coffee color with a correlation factor of 0.9387. The study continued looking for chemical indices: eleven indices were found to be linearly correlated to the color resulting from the roasting process, the most effective of them being 5-methyl furfural/2-acetyl furan ratio (index).Journal of Agricultural and Food Chemistry 10/2012; · 2.82 Impact Factor -
Article: Room temperature ionic liquids: New GC stationary phases with a novel selectivity for flavor and fragrance analyses.
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ABSTRACT: Ionic liquids (ILs) are of great interest as moderately polar to polar stationary phases for GC, because their selectivity differs markedly from that of conventionally used phases. In the flavor, fragrance and essential oil fields, analysts often deal with complex mixtures of compounds having similar structural and physical characteristics (e.g., mono- and sesquiterpenoids), therefore requiring an interactive combination between chromatographic and mass spectral data for correct identification. New GC stationary phases with different selectivity must therefore be continually tested. Performance and evolution over time of commercially available IL columns versus those commonly used in these fields are here evaluated, mainly in view of their routine use. Chromatographic and separative properties (efficiency, separation capability, inertness and/or activity) of commercially available IL columns were compared to those of columns coated with 5% phenyl-95% methylpolysiloxane, 14% cyanopropyl-86% polysiloxane, and polyethylene glycol, on different complexity samples, including standard mixtures of volatile suspected allergens and pesticides, and cornmint and vetiver essential oils. The results show that IL columns can successfully be used for a wide range of applications characteristic of these fields, mainly because of their unusual selectivity, in particular when separations based on functional groups are required. Moreover, the latest generation of IL columns (IL61 and IL60) presents chromatographic performance comparable to or only slightly lower than that of the conventional columns routinely used in these fields.Journal of chromatography. A 10/2012; · 4.19 Impact Factor -
Article: New medium-to-high polarity twister coatings for liquid and vapour phase sorptive extraction of matrices of vegetable origin.
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ABSTRACT: Stir Bar Sorptive Extraction (SBSE) is a solventless sampling technique first introduced to extract organic analytes from aqueous samples, in the following applied to headspace sampling (HeadSpace Sorptive Extraction - HSSE). In SBSE and HSSE, analytes are sorbed onto a thick film of polydimethylsiloxane (PDMS) coating a glass-coated magnet. However, PDMS is apolar and not highly effective in recovering polar analytes (i.e. with logK(o/w) below 2), making difficult their sampling in complex matrices. A new generation of medium-to-high polarity polymeric coatings for twisters i.e. polyethyleneglycol-modified silicone (EG) and polyacrylate/polyethyleneglycol (PA) has recently been introduced to overcome this limit. In this study, EG and PA twisters have been applied to SBSE and HSSE of a number of dedicated standard mixtures and real-world samples of vegetable origin to evaluate their capability to increase recovery of medium to highly polar analytes. The results obtained, expressed as percent concentration factor (CF%) versus PDMS twisters taken as reference, showed that analyte logK(o/w) is a key-factor driving the choice of the most effective coating. The new twisters showed to be successful for both SBSE and HSSE, although to a different extent. EG twisters gave high recoveries with analytes over a wide range of polarities and in particular with logK(o/w) below 2 and/or containing hydroxyl or carboxylic functional groups independently on their logK(o/w). On the other hand, PA twisters were selectively effective for highly polar compounds with logK(o/w) below 1.Journal of chromatography. A 10/2012; · 4.19 Impact Factor
