1,721,176 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
Separation of lipids
No full textLipid analysis and profiling is a crucial task in diverse fields including metabolomics, food analysis, pharmaceuticals, cosmetics, surfactants, fuels, and other commercial applications. As a consequence, lipid analysts have always been on the forefront of developments in separation science, greatly spurring the development of new techniques and methods of separation, including liquid chromatography. Consistent with the global trend toward greening of analytical procedures, a considerable effort has been put recently to implement alternative procedures that reduce or eliminate the use or generation of hazardous substances as well as energy consumption. As in any successful analytical methods, an efficient procedure for lipid analysis should be a flawless combination of extraction, separation, detection, and data processing; all these steps will be included in the discussion. Selection of the most suitable technique by lipid analysts ultimately requires a proper knowledge of the physical structure and location of the principal lipids present in a sample; this topic is therefore described in the chapter as well as the subject of lipid nomenclature and classification
Theoretical and practical aspects of LC-MS analysis
No full textDespite the early gloomy prospects for the development of a suitable interface and operation, instrumental couplings of liquid chromatography (LC) to mass spectrometry (MS) have experienced an enormous growth in the last two decades; the number of applications of this powerful hyphenated technique have exponentially increased, consistently. Arguably, the advances made in miniaturized LC systems and column technology have strongly prompted such an evolution; as a matter of fact, capillary LC-MS (and tandem MS) nowadays accounts for the vast majority of applications performed, e.g., through “omics” technologies. Today any mass spectrometer potentially can be hyphenated to an LC separation system by properly interfacing the chromatographic and spectrometric components; this was a major technical challenge earlier. Understanding the working principles and technical properties of different MS instruments gives an insight into the technical possibilities and limitations to be acknowledged when coupling MS with LC. In the sections that follow, the readers will be given theoretical and practical guidance on the analytical capabilities of most common types of MS analyzers, which constrain the utility of an instrument for handling the specific analytical task at hand
Characterization of essential oil of Pummelo (cv. Chandler) by GC-MS, HPLC and physicochemical indices
No full textExploitation of a unique mass spectral database with embedded linear retention index for volatile fraction characterisation of pistachios with different geographical origin
No full text
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
A flow-modulated comprehensive gas chromatography–mass spectrometry method for the analysis of fatty acid profiles in marine and biological samples
No full textThe present investigation is focused on the development of a flow-modulator (FM) comprehensive 2D GC (GC×GC)-quadrupole mass spectrometry (qMS) approach, for the analysis of fatty acids. A recently developed flow modulator interfaced an apolar–polar column set, and was used for the first time with a mass spectrometer. Method development was achieved by using a standard mixture, containing fatty acid methyl esters (FAMEs). The total run time was approx. 40 min, thus relatively rapid. The optimized FM GC×GC–qMS method was applied to marine and biological FAMEs. Validation parameters such as intraday and inter-day repeatability, limits of identification (mass spectral quality was evaluated at various FAME concentrations), and quantification were measured. Peak assignment was performed using pure standard compounds (when available), linear retention indices (LRIs), a dedicated FAME MS database, and specific bidimensional chromatogram positions. The MS database contained one-dimensional LRI information, exploited as a filter during the MS database search procedure. A good agreement was observed
between database LRI values, and those calculated on the twin-column set. The FM GC×GC–qMS method can be considered as a valid counterpart, with respect to cryogenically modulated GC×GC, in the fatty acid field of research
On 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
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