1,728,182 research outputs found
Optimized use of a 50 um internal diameter secondary column in a comprehensive two dimensional gas chromatography system
No full textThe focus of the present research is directed toward the
development of a comprehensive two-dimensional gas
chromatography (GC × GC) method, characterized by a
greatly increased separation power, if compared with GC
× GC approaches using classical column combinations.
The analytical objective was achieved by using a 0.05 mm
internal diameter (i.d.) capillary as second dimension, a
split-flow approach reported in previous research (Tranchida,
P. Q.; Casilli, A.; Dugo, P.; Dugo, G.; Mondello,
L. Anal. Chem. 2007, 79, 2266-2275), and a twin-oven
GC × GC instrument. The column combination employed
was an orthogonal one: an apolar 30 m × 0.25 mm i.d.
column was linked, by means of a Y-union, to a flame
ionization detector (FID)-connected high-resolution 1 m
× 0.05 mm i.d. polar one and to a 0.20 m × 0.05 mm
i.d. uncoated capillary segment; the latter was connected
to a manually operated split valve, located on top of the
second GC. As previously shown, the generation of
optimum gas linear velocities in both dimensions can be
attained by splitting gas flows at the outlet of the first
dimension (Tranchida, P. Q.; Casilli, A.; Dugo, P.; Dugo,
G.; Mondello, L. Anal. Chem. 2007, 79, 2266-2275).
An optimized GC × GC method was developed and
exploited for the analysis of a complex petrochemical
sample. The satisfactory results attained were directly
compared with those observed using the same instrumentation,
equipped with what can be defined as a
classical GC × GC split-flow column set: the same primary
column was connected to an FID-linked 1 m × 0.10 mm
i.d. polar one and to a 0.30 m × 0.10 mm i.d. uncoated
capillary. It will be herein illustrated that there is still
room for significant progress in the GC × GC field
Enhanced resolution comprehensive two-dimensional gas chromatography applied to the analysis of roasted coffee volatiles
No full textThe present research is based on the full exploitation of the separation power of a 0.05mm internal
diameter (ID) capillary, as a comprehensive two-dimensional (2D) GC (GC×GC) secondary column, with
the objective of attaining very high-resolution second dimension separations. The aim was achieved by
using a split-flow system developed in previous research [P.Q. Tranchida, A. Casilli, P. Dugo, G. Dugo,
L. Mondello, Anal. Chem. 79 (2007) 2266], and a dual-oven GC×GC instrument. The column combination
employed consisted of a polar 30m×0.25mm ID column connected, by means of a T union, to a
detector-linked high-resolution 1.1m×0.05mm ID apolar analytical column and to a 0.33m×0.05mm
ID retention gap; the latterwas connected to a manually operated split valve. As previously demonstrated,
the use of a split valve enables the regulation of gas flows through both analytical columns, generating the
most appropriate gas linear velocities. Comprehensive 2D GC experiments were carried out on Arabica
roasted coffee volatiles (previously extracted by means of solid-phase microextraction) with the splitvalve
closed (equal to what can be defined as conventional GC×GC) and with the split-valve opened at
various degrees. The reasons why it is absolutely not effective to use a 0.05mm ID column as second
dimension in a conventional GC×GC instrument will be discussed and demonstrated. On the contrary,
the use of a 0.05mm ID column as second dimension, under ideal conditions in a split-flow, twin-oven
system, will also be illustrated and discussed
LC-MS for the identification of oxygen heterocyclic compounds in citrus essential oils
No full textThe oxygen heterocyclic compounds (coumarins, psoralens and polymethoxylated flavones) present in the non-volatile residue of the essential oils of Mandarin, Sweet Orange, Bitter Orange, Bergamot and Grapefruit were analysed with an HPLC/API/MS system equipped with an APcI probe in positive mode. The use of hyphenated techniques, such as LC/MS provides a great information about the content and nature of constituents of natural complex matrices, such as essential oils. In this work, MS spectra were recorded at different voltages, to obtain structural information in addition to molecular weight information. The different response of the compounds identified has been also evaluated. The method allowed the confirmation of the identification of the main components of the fraction, previously reported for the different oils. MS characteristics of coumarins, psoralens and polymethoxylated flavones with different substitution patterns were determined on the basis of the response obtained with the APcI interface. Interface parameters were optimised to obtain a contemporaneous response for all the three classes of components. (C) 2000 Elsevier Science B.V
Characterization of essential oil of Pummelo (cv. Chandler) by GC-MS, HPLC and physicochemical indices
No full textOn the Genuineness of Citrus Essential Oils. Part LIII. Determination of the composition of the oxygen heterocyclic fraction of lemon essential oils (Citrus limon (L.) Burm. F.) by normal phase high performance liquid chromatography
No full textThe oxygen heterocyclic fraction of cold-pressed lemon essential oils has been studied by normal-
phase HPLC. The components of the fraction have been isolated by column chromatography, TLC and semi-
preparative HPLC with recycle. The identi®cation of the isolated components has been carried out by
1H-NMR and mass spectrometry. Three coumarins (5-geranyloxy-7-methoxycoumarin, citropten, 5-isopente-
nyloxy-7-methoxycoumarin) and ten psoralens (bergamottin, 8-geranyloxypsoralen, oxypeucedanin, byakange-
licol, oxypeucedanin hydrate, byakangelicin, imperatorin, phellopterin, isoimperatorin, 5-isopent-20-enyloxy-8-
(20,30-epoxyisopentyloxy)-psoralen) have been isolated and identi®ed. The main components were bergamottin
(160±291 mg/100 g of oil) and 5-geranyloxy-7-methoxycoumarin (180±250 mg/100 g of oil). Moreover,
herniarin, a coumarin characteristic of lime essential oil, has been detected. Herniarin had been reported
previously in essential oils obtained from Citrus limon L. var. Eureka
Authentication of Bergamot Essential Oil by Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometer (GC-C-IRMS)
No full textThe quality assessment of bergamot essential oils was established employing the gas chromatography-combustion-isotope ratio mass spectrometer (GC-C-IRMS) technique. An authenticity range was obtained investigating the carbon stable isotope ratio of genuine Italian bergamot essential oils (harvest period 2008-2009), in order to compare the GC-C-IRMS data of several industrial, commercial and foreign bergamot essential oil samples. Moreover, with the aim to test the efficiency and the sensibility of IRMS device, self-adulterated in laboratory bergamot oil samples were analyzed. The data were compared with those achieved by conventional enantioselective gas chromatography (Es-GC) and high resolution gas chromatography (GC-FID). Results of this work indicated that GC-C-IRMS was able not only to detect the presence of adulterants in the samples, hut also to discriminate the bergamot oil samples according to their geographic provenance and the nature of the adulterants added
Advances of Modern Gas Chromatography and Hyphenated Techniques for Analysis of Plant Extracts
No full textFree carotenoids and carotenoids esters composition in native orange juices of different varieties
No full textIntroduction. Among the citrus species, C. sinensis has
been the most studied given its importance in terms of production and its industrial
application in juices. Some of orange juice's organoleptic and functional properties,
which make it an attractive product for the consumer, are due to its carotenoid
composition. Xanthophylls can be found in either their free form (as the carotenes are
found) or in a more stable fatty acid esterified form in the case of mono- and
polyhydroxylated xanthophylls. Detection of adulteration of orange juices is of concern to
consumers, regulatory agencies and citrus processing industries, and the study of
carotenoid ester composition has been proposed to evaluate fruit products' authenticity.
In this study, we report on the native (carotenoid esters and free carotenoids) carotenoid
profile of orange juices of eight different varieties. Materials and methods.
Monovarietal fresh orange juices were obtained from squeezing mid-season oranges
(Citrus sinensis varieties: Bionda, Brasiliana, Moro, Ovale,
Sanguinello, Tarocco, Valence and Washington) cultivated and supplied by a local producer.
After the extraction of the carotenoids from the samples, the analyses were carried out by
HPLC-DAD-APCI-MS. Results and discussion. The results showed that, in the juices studied, the xanthophylls
were mostly esterified (93% of the total carotenoid mean content). The different varieties
investigated showed variations in their carotenoid contents. The total carotenoid contents
ranged from 2.42 µg·g–1 in the Washington variety to 15.8 µg·g–1 in
the Valencia variety. Among the monoesters, the Valencia variety showed the highest
violaxanthin ester amounts (61%), the Brasiliana variety showed the highest
β-cryptoxanthin ester content (86.9%) and the Tarocco variety had the highest luteoxanthin
ester amount (75.7%). Moreover, in general, in the Brasiliana, Ovale, Sanguinello,
Valencia and Washington varieties, the monoester contents were higher than the diesters,
whereas in the Bionda, Moro and Tarocco varieties the opposite was determined. To the best
of our knowledge, this is the first time that this analytical approach has been applied to
characterising, both qualitatively and quantitatively, the whole carotenoid pattern
(carotenoid esters and free carotenoids) in orange juices from the Bionda , Brasiliana,
Moro, Ovale, Sanguinello, Tarocco, Valence and Washington varieties. This contribution
could also be used to establish authenticity markers among orange varieties that could
potentially be used to prevent adulteration
Determination of hesperidin and naringin in bitter orange extract and the characterization of new nutraceuticals by innovative HPLC and capillary electrophoretic methods
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