186,338 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
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 selectivity and sensitivity of comprehensive two-dimensional gas chromatography combined with a novel high-speed triple quadrupole mass spectrometer
No full textENHANCED SELECTIVITY AND SENSITIVITY OF COMPREHENSIVE 2D GC COMBINED WITH A NOVEL FAST TRIPLE-QUAD MASS SPECTROMETER
No full textComprehensive two-dimensional gas chromatography (GC×GC), combined with mass
spectrometry (MS), is an extremely powerful three-dimensional technology, which has found
use only over the last decade. Very narrow peaks are generated in GC×GC applications, and
so MS systems must possess fast acquisition frequencies. For such a reason, low-resolution
high-speed time-of-flight (ToF) systems have been the most popular choice in the field, followed
by rapid-scanning single quadrupole (q) instruments. The main scopes of most such GC×GCToF
MS and GC×GC-qMS applications, have been the quantitative and/or qualitative analysis
of untargeted solutes. There has been only a low number of cases in which other MS-types
have been employed, a fact related to their slow spectral production rates. The present
investigation is focused on the use and first evaluation of a novel high-speed triple quadrupole
(QqQ) mass spectrometer, in flow-modulated GC×GC applications. The QqQ MS instrument
can be operated simultaneously in the full scan and multiple reaction monitoring (MRM) modes,
under the high spectral production frequencies required for GC×GC quali/quantitative
determinations. It will be shown that, in the same GC×GC-QqQ MS application, both full-scan
spectra relative to unknown compounds, and MS-MS data relative to known ones, can be
attained, killing two birds with one stone. Obviously, a great increase both in sensitivity and
selectivity were attained in the MRM mode. GC×GC-QqQ MS applications on real-world food
samples, containing contaminants at the sub-ppb level, will be illustrated and discussed
INCREASING THE SELECTIVITY AND SENSITIVITY OF COMPREHENSIVE TWO- DIMENSIONAL GAS CHROMATOGRAPHY BY HYPHENATION WITH A NOVEL HIGH- SPEED TRIPLE-QUADRUPOLE MASS SPECTROMETER
No full textComprehensive two-dimensional gas chromatography (GC×GC) has been widely used in
combination with mass spectrometry (MS), only throughout the last decade. With regards to
the mass-spectrometric instrumentation type used, low-resolution high-speed time-of-flight
(ToF) systems have been the most popular choice, followed by rapid-scanning low-resolution single quadrupole instruments. The main objectives of most such GC×GC-MS applications have been the quantitative and/or qualitative determination of untargeted analytes. There has been only a low number of publications describing the use of other MS-types, a fact related to slow spectral production rates. The requirement for high-speed MS systems is related to the
very fast second-dimension separations. The present investigation is focused on the exploitation of a novel high-speed triple quadrupole (QqQ) mass spectrometer, in flow-modulated GC×GC applications. The QqQ MS is capable of operation in the simultaneous full-scan/MRM (multiple reaction monitoring) mode, under the high-speed spectral production conditions required for GC×GC identification and quantification. It will be shown that, in the same GC×GC-QqQ MS
analysis, both full-scan spectra relative to untargeted compounds, and MS-MS spectra relative
to targeted ones, can be attained. Obviously, the use of the MRM mode enables a great increase
both in sensitivity and selectivity. A GC×GC-QqQ MS application on an essential oil, containing
contaminants at the sub-ppb level, will be illustrated and discussed
Flow-modulated Comprehensive 2D Gas Chromatography-Mass Spectrometry assisted by a novel data-processing software
No full textOver the last decade, several cryogenic modulators have been developed, and found application in the comprehensive two-dimensional gas chromatography (GC×GC) field. Although the effectiveness of such a modulation approach is not under discussion, it is also a rather expensive issue. Consequently, the concept and development of low-costing flow modulation methods is of high interest.
The present lecture is focused on the development and use of a highly flexible, chip-based flow modulator for comprehensive two-dimensional gas chromatography. The novel modulation system consists of a metallic disc (chip), with internal channels, located entirely within the GC oven; apart from the two dimensions, the disc is linked to an auxiliary pressure unit, and is characterized by an interchangeable sample loop, which simplifies the optimization step and maximizes the overall GC×GC performance. The valve part of the modulator is located outside the GC oven, and, hence, there are no temperature restrictions.
A series of flow-modulated GC×GC-MS applications will be shown, relative to a variety of complex real-world samples. The data processing step was simplified by use of a novel, user-friendly comprehensive chromatography software
Estimating the nucleation ability of various surfaces towards isotactic polypropylene via light intensity induction time measurements
No full textCrystallization of isotactic polypropylene (iPP) at the interface with crystalline films of two commercially employed nucleating agents (sodium benzoate (NaBz) and sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl)phosphate (NA-11)) and with a glass fiber (GF) was investigated using a polarized optical microscope. The analysis of the light intensity evolution during the crystallization process enabled the successful estimation of the time at which the crystal growth began, i.e., the induction time (ti), at various crystallization temperatures. Meaningful differences in the ti values were observed between the investigated systems. Moreover, the ti data have been analyzed according to different nucleation models proposed in the literature, which consider either the time to form the first crystalline layer in contact with the substrate or the time required to grow a cluster of critical size. It has been found that the two models are applicable in different temperature ranges depending on the efficiency of the given substrate. Therefore, in order to obtain the value of the surface free energy difference function, Δσ, which is directly related to the nucleation energy barrier and useful for the definition of a universal nucleating efficiency scale, a model that considers both the above-mentioned times was fitted to the overall data. The values of Δσ for the nucleation of iPP on the surface of the different substrates are thus obtained and discussed in the framework of the literature results
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
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