René Vreuls - Academia.edu (original) (raw)
Papers by René Vreuls
Chemosphere, 2006
The identity of compounds responsible for estrogenic and dioxin-like activities in sediment from ... more The identity of compounds responsible for estrogenic and dioxin-like activities in sediment from the harbour of the small town Zierikzee in Zeeland, The Netherlands, was investigated using a bioassay directed fractionation approach with the in vitro estrogen and dioxin responsive reporter gene assays ER- and DR-CALUX. For identification of compounds exhibiting activity in the bioassays, either one or two-dimensional GC in combination with quadrupole (MSD), ion trap (ITD) or time-of-flight mass spectrometric detection (ToF-MS) was used, depending on the biological and chemical characteristics and the complexity of the fractions. The natural estrogenic hormone 17-beta-estradiol and its metabolite estrone were identified with GC-ITD as the main contributors to the estrogenic activity. After successive rounds of fractionation, the dioxin-like activity could be explained by the presence of various polycyclic aromatic hydrocarbons identified with GC-MSD and two-dimensional comprehensive GC x GC-ToF-MS. Some estrogenic activity of a relatively non-polar nature remained unidentified.
Journal of Chromatography A, 2011
In gas chromatography (GC) reproducible retention times are in many cases highly favorable or in ... more In gas chromatography (GC) reproducible retention times are in many cases highly favorable or in some cases even required. In one-dimensional GC, retention time shifts can be eliminated or minimized using a procedure called retention time locking (RTL). This procedure is based on adjusting the (constant) column head pressure. Unfortunately, this RTL procedure cannot be used in comprehensive two-dimensional gas chromatography (GC×GC) given the fact that peaks will shift in both dimensions. Adjusting the column head pressure in GC×GC will only minimize or eliminate the primary retention time shifts. In this paper, a fast and easy to perform, two-step retention time locking procedure for two-dimensional gas chromatography (2D-RTL) is proposed and its feasibility is demonstrated. This 2D-RTL procedure involves adjustment of the column head pressure or constant column flow, followed by the adjustment of the so-called effective secondary column length. The secondary column length is increased or decreased, simply by moving it stepwise through the modulator. It is demonstrated that retention time shifts in both the primary- and secondary-dimension, which may occur after e.g. replacing the column set, can be minimized to less than half peak base width. The proposed 2D-RTL procedure is used successfully for approximately 1 year in our laboratory.
Chromatographia, 2001
Summary Use of a large-volume injection system with a solvent vapour exit (SVE) requires optimis... more Summary Use of a large-volume injection system with a solvent vapour exit (SVE) requires optimisation. An appropriate strategy is to determine the evaporation rate by increasing the injection time at a fixed injection speed, injection temperature and head pressure. When measuring the flow rate in the carrier gas supply line to the on-column injector, optimisation can be very rapid: some five
Analytical Chemistry, 2007
Chromatographia, 2002
... Key Words Comprehensive ~o-dimensional gas chromatography Cryogen ic mod u lation Solid-phase... more ... Key Words Comprehensive ~o-dimensional gas chromatography Cryogen ic mod u lation Solid-phase micro-extraction Flavours Foodstuffs Summary ... This ap-proach (HS-SPME-GC xGC-FID) is distinctly superior to use of one-dimensional GC, ie, HS-SPME-GC-FID. ...
Journal of Chromatography A
Journal of Chromatography A, 2005
Journal of chromatography. A, 2005
The principles, practicability and potential of comprehensive two-dimensional (2D) gas chromatogr... more The principles, practicability and potential of comprehensive two-dimensional (2D) gas chromatography coupled to a rapid-scanning quadrupole mass spectrometer (GC x GC-qMS) for the analysis of complex flavour mixtures in food, allergens in fragrances and polychlorinated biphenyls (PCBs) were studied. With a scan speed of 10,000 amu/s, monitoring over a mass range of up to 200 atomic mass unit (amu) can be achieved at an acquisition frequency of 33 Hz. Extending this mass range and/or increasing the data acquisition frequency results in a loss of spectral quality. Optimal parameter settings allow, next to unambiguous identification/confirmation of target compounds on the basis of high-quality mass spectra, fully satisfactory quantification (three to four modulations per peak) with linear calibration plots and detection limits in the low-pg level. The potential of time-scheduled data acquisition to increase the effective mass range within one GC x GC run was also explored. The analyse...
Journal of Chromatography A
Atmospheric Chemistry and Physics, Feb 27, 2003
Journal of Chromatography A, 1999
A multiresidue method based on matrix solid-phase dispersion (MSPD) microextraction was studied t... more A multiresidue method based on matrix solid-phase dispersion (MSPD) microextraction was studied to determine the carbamate, benfuracarb, and urea insecticides, diflubenzuron, flufenoxuron hexaflumuron and hexythiazox, used in control of citrus pests. Optimisation of different parameters, such as the type of solid support for matrix dispersion, elution solvents and the clean-up step were carried out. The method used 0.5 g of orange sample, C8 bonded silica as MSPD sorbent and dichloromethane as eluting solvent. Recoveries, at spiked concentrations below the maximum residue levels established by Spanish Government, were between 74 and 84% with relative standard deviations ranging from 2 to 4%. The limits of quantification were from 0.15 to 0.25 microgram/g using high-performance liquid chromatography with UV detection at 200 nm. The method may be useful as a screening protocol for the determination of these newly developed pesticides in citrus samples.
Spectra 2000 Analyse, 2001
In this study, two new capillary GC techniques have been coupled to time-of-flight mass spectrome... more In this study, two new capillary GC techniques have been coupled to time-of-flight mass spectrometry (TOF-MS). The capability of fast scanning, the linearity of response and low detection limits make this MS technique the detection system of choice for fast GC. Existing GC approaches can be carried out within 5 min using short narrow-bore columns. The quality of spectra and the absence of skewing enable chemometrical spectral peak deconvolution. The software allowed calculation of spectra from overlapping peaks, which elution times differed by three scans only. Selected examples show limits of detection in the low pg range for organophosphorus pesticides (1-6 pg), triazine herbicides (4-60 pg) and polycyclic aromatic hydrocarbons (0.3-6 pg). For real-life samples detection limits of the microcontaminants were at 0.1 μg/l in surface water and at 0.01 mg/kg in sediment. The analytes were extracted from surface water (50 ml sample into 50 μl of ethyl acetate using solid-phase extraction) and sediment (2 g sample into 2 ml of n-hexane using ultrasonic assisted liquid extraction), of which 1 pl of the extract was injected into the GC system using a split injector. In this communication only results for triazine herbicides are shown. Coupling of TOF-MS with comprehensive two-dimensional GC (GCxGC) results in a unique three-dimensional separation of analytes. The technique is especially suitable for analysis of very complex mixtures and extracts. GCxGC increases the overall separation power, because each analyte is separated on two different stationary phases. Peak widths in the order of 50-100 ms are obtained, which requires TOF-MS if identification has to be included. As a consequence of the peak compression in the interface, sensitivity is increased.
Journal of chromatography. A, Jan 4, 2008
TrAC Trends in Analytical Chemistry, 2006
... years of GC × GC studies, detection had therefore to be performed with a flame-ionization det... more ... years of GC × GC studies, detection had therefore to be performed with a flame-ionization detector ... Despite its low acquisition rate of 10 Hz, an atomic emission detector (AED) was found to ... resulted in second-dimension peak widths similar to those generated by the digital FID. ...
Journal of Chromatography A - J CHROMATOGR A, 2002
The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced ... more The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced by using comprehensive two-dimensional GC (GC×GC) instead. Combination with mass spectrometric detection is desirable for unambiguous confirmation of target compounds and the provisional identification of unknowns. A GC×GC system using a cryogenic modulator was coupled to a time-of-flight mass spectrometric (TOF MS) detector. With the determination of pesticides in vegetable extracts as an example, it was demonstrated that GC×GC improves the separation dramatically. All 58 pesticides of interest could be identified using their full-scan mass spectra, which was not possible when using 1D-GC–TOF MS. In addition, the high scan speed of the TOF MS allowed the deconvolution of compounds partly co-eluting in GC×GC.
International Journal of Environmental Analytical Chemistry, 1999
A system for the automated monitoring of organic pollutants in surface waters (SAMOS) has been de... more A system for the automated monitoring of organic pollutants in surface waters (SAMOS) has been developed over the last 5 years to monitor for the presence of organic contaminants in surface water. It uses a solid-phase extraction (SPE) trace enrichment step followed by on-line elution and separation by HPLC. Detection and provisional identification is obtained with diode array detection. For
Journal of Chromatography A, 2000
Journal of Chromatography A, 2003
The practicability and potential of comprehensive two-dimensional gas chromatography coupled to t... more The practicability and potential of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOF-MS) for the analysis of complex flavour mixtures in food were studied. With the determination of key flavour targets in dairy samples as an example, it was demonstrated that GC×GC dramatically improves the separation. As a consequence, identification and, more importantly, quantification down to the ng/g
Journal of Chromatography A, 2002
The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced ... more The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced by using comprehensive two-dimensional GC (GC×GC) instead. Combination with mass spectrometric detection is desirable for unambiguous confirmation of target compounds and the provisional identification of unknowns. A GC×GC system using a cryogenic modulator was coupled to a time-of-flight mass spectrometric (TOF MS) detector. With the determination of pesticides
Chemosphere, 2006
The identity of compounds responsible for estrogenic and dioxin-like activities in sediment from ... more The identity of compounds responsible for estrogenic and dioxin-like activities in sediment from the harbour of the small town Zierikzee in Zeeland, The Netherlands, was investigated using a bioassay directed fractionation approach with the in vitro estrogen and dioxin responsive reporter gene assays ER- and DR-CALUX. For identification of compounds exhibiting activity in the bioassays, either one or two-dimensional GC in combination with quadrupole (MSD), ion trap (ITD) or time-of-flight mass spectrometric detection (ToF-MS) was used, depending on the biological and chemical characteristics and the complexity of the fractions. The natural estrogenic hormone 17-beta-estradiol and its metabolite estrone were identified with GC-ITD as the main contributors to the estrogenic activity. After successive rounds of fractionation, the dioxin-like activity could be explained by the presence of various polycyclic aromatic hydrocarbons identified with GC-MSD and two-dimensional comprehensive GC x GC-ToF-MS. Some estrogenic activity of a relatively non-polar nature remained unidentified.
Journal of Chromatography A, 2011
In gas chromatography (GC) reproducible retention times are in many cases highly favorable or in ... more In gas chromatography (GC) reproducible retention times are in many cases highly favorable or in some cases even required. In one-dimensional GC, retention time shifts can be eliminated or minimized using a procedure called retention time locking (RTL). This procedure is based on adjusting the (constant) column head pressure. Unfortunately, this RTL procedure cannot be used in comprehensive two-dimensional gas chromatography (GC×GC) given the fact that peaks will shift in both dimensions. Adjusting the column head pressure in GC×GC will only minimize or eliminate the primary retention time shifts. In this paper, a fast and easy to perform, two-step retention time locking procedure for two-dimensional gas chromatography (2D-RTL) is proposed and its feasibility is demonstrated. This 2D-RTL procedure involves adjustment of the column head pressure or constant column flow, followed by the adjustment of the so-called effective secondary column length. The secondary column length is increased or decreased, simply by moving it stepwise through the modulator. It is demonstrated that retention time shifts in both the primary- and secondary-dimension, which may occur after e.g. replacing the column set, can be minimized to less than half peak base width. The proposed 2D-RTL procedure is used successfully for approximately 1 year in our laboratory.
Chromatographia, 2001
Summary Use of a large-volume injection system with a solvent vapour exit (SVE) requires optimis... more Summary Use of a large-volume injection system with a solvent vapour exit (SVE) requires optimisation. An appropriate strategy is to determine the evaporation rate by increasing the injection time at a fixed injection speed, injection temperature and head pressure. When measuring the flow rate in the carrier gas supply line to the on-column injector, optimisation can be very rapid: some five
Analytical Chemistry, 2007
Chromatographia, 2002
... Key Words Comprehensive ~o-dimensional gas chromatography Cryogen ic mod u lation Solid-phase... more ... Key Words Comprehensive ~o-dimensional gas chromatography Cryogen ic mod u lation Solid-phase micro-extraction Flavours Foodstuffs Summary ... This ap-proach (HS-SPME-GC xGC-FID) is distinctly superior to use of one-dimensional GC, ie, HS-SPME-GC-FID. ...
Journal of Chromatography A
Journal of Chromatography A, 2005
Journal of chromatography. A, 2005
The principles, practicability and potential of comprehensive two-dimensional (2D) gas chromatogr... more The principles, practicability and potential of comprehensive two-dimensional (2D) gas chromatography coupled to a rapid-scanning quadrupole mass spectrometer (GC x GC-qMS) for the analysis of complex flavour mixtures in food, allergens in fragrances and polychlorinated biphenyls (PCBs) were studied. With a scan speed of 10,000 amu/s, monitoring over a mass range of up to 200 atomic mass unit (amu) can be achieved at an acquisition frequency of 33 Hz. Extending this mass range and/or increasing the data acquisition frequency results in a loss of spectral quality. Optimal parameter settings allow, next to unambiguous identification/confirmation of target compounds on the basis of high-quality mass spectra, fully satisfactory quantification (three to four modulations per peak) with linear calibration plots and detection limits in the low-pg level. The potential of time-scheduled data acquisition to increase the effective mass range within one GC x GC run was also explored. The analyse...
Journal of Chromatography A
Atmospheric Chemistry and Physics, Feb 27, 2003
Journal of Chromatography A, 1999
A multiresidue method based on matrix solid-phase dispersion (MSPD) microextraction was studied t... more A multiresidue method based on matrix solid-phase dispersion (MSPD) microextraction was studied to determine the carbamate, benfuracarb, and urea insecticides, diflubenzuron, flufenoxuron hexaflumuron and hexythiazox, used in control of citrus pests. Optimisation of different parameters, such as the type of solid support for matrix dispersion, elution solvents and the clean-up step were carried out. The method used 0.5 g of orange sample, C8 bonded silica as MSPD sorbent and dichloromethane as eluting solvent. Recoveries, at spiked concentrations below the maximum residue levels established by Spanish Government, were between 74 and 84% with relative standard deviations ranging from 2 to 4%. The limits of quantification were from 0.15 to 0.25 microgram/g using high-performance liquid chromatography with UV detection at 200 nm. The method may be useful as a screening protocol for the determination of these newly developed pesticides in citrus samples.
Spectra 2000 Analyse, 2001
In this study, two new capillary GC techniques have been coupled to time-of-flight mass spectrome... more In this study, two new capillary GC techniques have been coupled to time-of-flight mass spectrometry (TOF-MS). The capability of fast scanning, the linearity of response and low detection limits make this MS technique the detection system of choice for fast GC. Existing GC approaches can be carried out within 5 min using short narrow-bore columns. The quality of spectra and the absence of skewing enable chemometrical spectral peak deconvolution. The software allowed calculation of spectra from overlapping peaks, which elution times differed by three scans only. Selected examples show limits of detection in the low pg range for organophosphorus pesticides (1-6 pg), triazine herbicides (4-60 pg) and polycyclic aromatic hydrocarbons (0.3-6 pg). For real-life samples detection limits of the microcontaminants were at 0.1 μg/l in surface water and at 0.01 mg/kg in sediment. The analytes were extracted from surface water (50 ml sample into 50 μl of ethyl acetate using solid-phase extraction) and sediment (2 g sample into 2 ml of n-hexane using ultrasonic assisted liquid extraction), of which 1 pl of the extract was injected into the GC system using a split injector. In this communication only results for triazine herbicides are shown. Coupling of TOF-MS with comprehensive two-dimensional GC (GCxGC) results in a unique three-dimensional separation of analytes. The technique is especially suitable for analysis of very complex mixtures and extracts. GCxGC increases the overall separation power, because each analyte is separated on two different stationary phases. Peak widths in the order of 50-100 ms are obtained, which requires TOF-MS if identification has to be included. As a consequence of the peak compression in the interface, sensitivity is increased.
Journal of chromatography. A, Jan 4, 2008
TrAC Trends in Analytical Chemistry, 2006
... years of GC × GC studies, detection had therefore to be performed with a flame-ionization det... more ... years of GC × GC studies, detection had therefore to be performed with a flame-ionization detector ... Despite its low acquisition rate of 10 Hz, an atomic emission detector (AED) was found to ... resulted in second-dimension peak widths similar to those generated by the digital FID. ...
Journal of Chromatography A - J CHROMATOGR A, 2002
The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced ... more The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced by using comprehensive two-dimensional GC (GC×GC) instead. Combination with mass spectrometric detection is desirable for unambiguous confirmation of target compounds and the provisional identification of unknowns. A GC×GC system using a cryogenic modulator was coupled to a time-of-flight mass spectrometric (TOF MS) detector. With the determination of pesticides in vegetable extracts as an example, it was demonstrated that GC×GC improves the separation dramatically. All 58 pesticides of interest could be identified using their full-scan mass spectra, which was not possible when using 1D-GC–TOF MS. In addition, the high scan speed of the TOF MS allowed the deconvolution of compounds partly co-eluting in GC×GC.
International Journal of Environmental Analytical Chemistry, 1999
A system for the automated monitoring of organic pollutants in surface waters (SAMOS) has been de... more A system for the automated monitoring of organic pollutants in surface waters (SAMOS) has been developed over the last 5 years to monitor for the presence of organic contaminants in surface water. It uses a solid-phase extraction (SPE) trace enrichment step followed by on-line elution and separation by HPLC. Detection and provisional identification is obtained with diode array detection. For
Journal of Chromatography A, 2000
Journal of Chromatography A, 2003
The practicability and potential of comprehensive two-dimensional gas chromatography coupled to t... more The practicability and potential of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOF-MS) for the analysis of complex flavour mixtures in food were studied. With the determination of key flavour targets in dairy samples as an example, it was demonstrated that GC×GC dramatically improves the separation. As a consequence, identification and, more importantly, quantification down to the ng/g
Journal of Chromatography A, 2002
The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced ... more The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced by using comprehensive two-dimensional GC (GC×GC) instead. Combination with mass spectrometric detection is desirable for unambiguous confirmation of target compounds and the provisional identification of unknowns. A GC×GC system using a cryogenic modulator was coupled to a time-of-flight mass spectrometric (TOF MS) detector. With the determination of pesticides