1,721,014 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
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
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
Evaluation of a novel helium ionization detector within the context of (low-)flow modulation comprehensive two-dimensional gas chromatography
No full textThe present research is focused on the use and evaluation of a novel helium ionization detector, defined as barrier discharge ionization detector (BID), within the context of (low-)flow modulation comprehensive two-dimensional gas chromatography (FM GC. ×. GC). The performance of the BID device was compared to that of a flame ionization detector (FID), under similar FM GC. ×. GC conditions.Following development and optimization of the FM GC. ×. GC method, the BID was subjected to fine tuning in relation to acquisition frequency and discharge flow. Moreover, the BID performance was measured and compared to that of the FID, in terms of extra-column band broadening, sensitivity and dynamic range. The comparative study was carried out by using standard compounds belonging to different chemical classes, along with a sample of diesel fuel. Advantages and disadvantages of the BID system, also within the context of FM GC. ×. GC, are critically discussed. In general, the BID system was characterized by a more limited dynamic range and increased sensitivity, compared to the FID. Additionally, BID and FID contribution to band broadening was found to be similar under the operational conditions applied.Particular attention was devoted to the behaviour of the FM GC. ×. GC-BID system toward saturated and aromatic hydrocarbons, for a possible future use in the field of mineral-oil food contamination research
In-pipette solid-phase extraction prior to flow-modulation comprehensive two-dimensional gas chromatography with dual detection for the determination of minor components in vegetable oils
No full textThe present research is based on the development of an effective, environmentally-friendly and low-cost method for investigation of minor components in vegetable oils, exploiting the advantages of a miniaturized solid-phase extraction (SPE) and the potential of flow modulation (FM) comprehensive two-dimensional gas chromatography (GC×GC), coupled to a mass spectrometer (MS) and a flame ionization detector (FID). The initial sample preparation step was carried out using a miniaturized approach characterized by a SPE process in a Pasteur pipette. Then, the isolated fraction was injected into an FM GC×GC system. Tentative identification was carried out by means of MS spectral information, while quantification was carried out by using the FID data. Four different vegetable oil samples were analyzed using the proposed method, namely an extra virgin olive oil (EVO), a hazelnut oil (HO), a borage oil, and an EVO/HO mixture
Is mineral oil contamination really mineral oil? Detailed elucidation by using comprehensive two dimensional gas chromatography with dual detection
No full textMineral oil is a quite widespread contaminant of foods. It
derives from different sources, but more recently attention
has been focused mainly on paperboard packaging. Such a
contamination derives from the offset printing inks applied
directly to the packaging, and/or from the ink present in the
recycled fibers used (generally deriving from newspapers).
Mineral oil contains proportions of mineral oil saturated
hydrocarbons (MOSH, including n-alkanes, isoalkanes and
cycloalkanes), and mineral oil aromatic hydrocarbons
(MOAH), which both are characterized by humps of
unresolved complex mixtures (UCM) after gas
chromatographic (GC) analysis. Resolution can be greatly
improved using a comprehensive multidimensional GC
(GC×GC) approach, which allows to define a more detailed
profile of the compound distribution in the unresolved hump,
especially for the MOAH fraction, where compounds can be
separated according to the number of rings. Despite the lack
of structural information (obtainable using a mass
spectrometer – MS - detector), the flame ionization detector
(FID) is the detector of choice to reliably quantify such
humps, because FIDs provide virtually the same response
per unit of mass of hydrocarbons, on the contrary of the MS
detector. Moreover the lack of a proper calibration standard
is a serious quantification problem in MS analysis. The aim
of the present work is to develop a method to simultaneously
quantify and confirm mineral oil contamination, by using
GC×GC with dual detection: FID for quantification purposes,
and MS for confirmation. The MOSH and MOAH fraction
were separated by using an SPE cartridge, manually packed
with silvered silica gel (Ag-SPE), before injection in the
GC×GC system. The presence of interfering compounds, in
the fraction of interest, can be determined both by the
position in the bidimensional plot and the mass spectrum
profile acquired simultaneously. The quantitative results
(both for the MOSH and the MOAH fractions) obtained were
compared with those derived by performing large volume
injection (LVI) GC–FID, after the same Ag-SPE fractionation
step, and through a hyphenated liquid-gas chromatographic
system (LC–GC)
Flow-modulation comprehensive two-dimensional enantio-gas chromatography: A valid and flexible alternative to heart-cutting multidimensional enantio-gas chromatography
No full textThe present research is focused on the proposal of use of flow-modulation comprehensive two-dimensional enantio-gas chromatography (FM eGC × GC) as a valid, flexible, and possibly superior alternative to heart-cutting multidimensional enantio-GC (eMDGC). The latter, a technique of demonstrated utility, is used specifically for the targeted separation of chiral compounds, whereas FM eGC × GC can produce both targeted and high-resolution untargeted information in a single run. It is clearly possible to use eMDGC for untargeted analysis, often with a flame ionization detector (stand-by analysis), to monitor a first-dimension (1D) separation, of much lower peak capacity compared to FM eGC × GC. If eMDGC is used with mass spectrometry (MS), it is normally exploited to monitor the second-dimension (2D) separation. The analytical instrument consisted of automated solid-phase microextraction (SPME), and a low duty-cycle FM eGC × GC system (with time-of-flight MS), equipped with an enantioselective 1D column (2,3-di-O-methyl-6-t-butyl silyl β-cyclodextrin derivative) and a 2D polyethylene glycol one. Ten Marsala wines were subjected to analysis, for the determination of chiral lactones (many at the low ppb level, due to the high concentration capacity of SPME) and for general analyte profiling. In many instances, highly complex chromatograms were attained, with statistical analysis (ANOVA-simultaneous component analysis and partial least squares discriminant analysis) used for sample differentiation
Fast gas chromatography combined with a high-speed triple quadrupole mass spectrometer for the analysis of unknown and target citrus essential oil volatiles
No full textpeer reviewe
Gas velocity at the point of re-injection: An additional parameter in comprehensive two-dimensional gas chromatography optimization
No full textpeer reviewe
Determination of saturated-hydrocarbon contamination in baby foods by using on-line liquid-gas chromatography and off-line liquid comprehensive gas chromatography combined with mass spectrometry
No full textThe present contribution describes an investigation directed towards the use of a rapid heart-cutting multidimensional LC–GC–FID method for the analysis of mineral oil saturated hydrocarbons (MOSH), contained in different types of homogenized solid baby food (fish, meat and fruit products). The fish and meat products all contained vegetable oil (sunflower), potentially an important source of mineral-oil contamination. Sixteen commercial baby food samples were subjected to analysis, with various degrees of MOSH contamination (from 0.3 mg/kg to circa 14 mg/kg) found. Hence, MOSH contamination was found not only in the meat and fish products, but also in the fruit ones. A fruit-based baby food was lab-made, using the ingredients reported on the commercial product, and was found to be contaminated. The single
ingredients were then subjected to LC–GC analysis, with corn starch and sugar found to be the source of contamination. For confirmation of the analytical findings, three of the sixteen samples were analyzed in two separate laboratories, using two distinct LC–GC methods, based on different interfaces.
The results were confirmed, in qualitative terms, by collecting the LC fractions, relative to some of the food samples, and subjecting them to comprehensive two-dimensional GC-quadrupole mass spectrometry. Thus, mass spectral data were attained for the saturated hydrocarbons.The present contribution describes an investigation directed towards the use of a rapid heart-cutting multidimensional LC-GC-FID method for the analysis of mineral oil saturated hydrocarbons (MOSH), contained in different types of homogenized solid baby food (fish, meat and fruit products). The fish and meat products all contained vegetable oil (sunflower), potentially an important source of mineral-oil contamination. Sixteen commercial baby food samples were subjected to analysis, with various degrees of MOSH contamination (from 0.3. mg/kg to circa 14. mg/kg) found. Hence, MOSH contamination was found not only in the meat and fish products, but also in the fruit ones. A fruit-based baby food was lab-made, using the ingredients reported on the commercial product, and was found to be contaminated. The single ingredients were then subjected to LC-GC analysis, with corn starch and sugar found to be the source of contamination. For confirmation of the analytical findings, three of the sixt..
- …
