High-throughput analysis of human serum for selected polychlorinated biphenyls (PCBs) by gas chromatography-isotope dilution time-of-flight mass spectrometry (GC-IDTOFMS)

Comprehensive Two-Dimensional Gas Chromatography Mass Spectrometry-Based Metabolomics

Compared to one-dimensional gas chromatography with mass spectrometry (GC-MS), GC × GC-MS provides significantly increased peak capacity, resolution, and sensitivity for analysis of complex biological samples. In the last decade, GC × GC-MS has been increasingly applied to the discovery of metabolite biomarkers and elucidation of metabolic mechanisms in human diseases. The recent development of coupling GC × GC with a high-resolution mass spectrometer further accelerates these metabolomic applications. In this chapter, we will briefly review the instrumentation, sample preparation, data analysis, and applications of GC × GC-MS-based metabolomic analysis.

β-Cyclodextrin coated SiO2@Au@Ag core–shell nanoparticles for SERS detection of PCBs

A new type of surface-enhanced Raman scattering (SERS) substrate consisting of β-cyclodextrin (β-CD) coated SiO₂@Au@Ag nanoparticles (SiO₂@Au@Ag@CD NPs) has been achieved.

Hydrophobic gold nanostructures via electrochemical deposition for sensitive SERS detection of persistent toxic substances

The hydrophobic gold nanostructures were used for direct SERS detection of PTS with high sensitivity.

Label-free selective SERS detection of PCB-77 based on DNA aptamer modified SiO₂@Au core/shell nanoparticles

A label-free approach to selective detection of 3,3',4,4'-tetrachlorobiphenyl (PCB77) using aptamer modified silica-Au/core-shell nanoparticles (denoted as SiO2@Au core/shell NPs) through surface enhanced Raman scattering (SERS) spectroscopy was proposed. The devised system consisted of SiO2@Au core/shell NPs fixed on the amino-silane functionalized glass slides with the PCB77-binding aptamers attached covalently to the gold surfaces through a thiol linker. The aptamers made of single-stranded DNA (ssDNA) oligomers with one end standing on the Au surface changed the conformation upon conjugation with PCB77, which correspondingly caused the spectral response of the ssDNA oligomers. The intensity ratio I(660 cm(-1))/I(736 cm(-1)) decreased with the amount of PCB77 added, which thus allowed us to measure trace amounts of PCB77 in a selective and quantitative way. This work therefore demonstrates that the design of aptamer-modified SiO2@Au core/shell NPs can be utilized for label-free SERS detection of persistent organic pollutants (POPs) in the environment.

Electrochemical impedance determination of polychlorinated biphenyl using a pyrenecyclodextrin-decorated single-walled carbon nanotube hybrid

This work reports the first detailed study on an electrochemical impedance sensor for determination of polychlorinated biphenyl (PCB), such as 3,3',4,4'-tetrachlorobiphenyl (PCB-77), based on a single-walled carbon nanotube/pyrenecyclodextrin (SWCNT/PyCD) hybrid.

Comprehensive two-dimensional gas chromatography time of flight mass spectrometry (GC×GC-TOFMS) for environmental forensic investigations in developing countries

The disposal and dumping of toxic waste is a matter of growing concern in developing countries, including South Africa. Frequently these countries do not possess access to gas chromatography-high resolution mass spectrometry (GC-HRMS) for the determination of persistent organic pollutants (POPs). This publication describes an alternative approach to the investigation of toxic waste using comprehensive gas chromatography coupled to time of flight mass spectrometry (GC×GC-TOFMS). The technology permits both comprehensive screening of toxic samples for numerous classes of organic pollutants and also quantitative analysis for the individual compounds. This paper describes the use of this technique by analysing samples obtained from a hazardous waste treatment facility in South Africa. After sampling and extraction the samples were analysed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and four dioxin-like non-ortho substituted polychlorinated biphenyls (PCBs). The quantitative values, as well as detection limits, obtained using the GC×GC-TOFMS methodology compares well with those obtained using GC-HRMS; the accepted benchmark technology for this analysis. Although GC×GC-TOFMS is not a target compound analytical technique (as is GC-HRMS), it is possible to obtain information on numerous other classes of organic pollutants present in the samples in one analytical run. This is not possible with GC-HRMS. Several different column combinations have been investigated for handling very complex waste samples and suggestions are presented for the most suitable combination.

High throughput method for the determination of organochlorine pesticides and polychlorinated biphenyls in human serum

An improved method for the determination of selected organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in human serum was developed. The method requires low volume of serum (500 microl) and 48-96 samples per day can be prepared by one analyst without special automatic equipment. Initial extraction was performed using 96-well solid-phase extraction disk plates and was followed by a clean-up with silica gel/sulfuric acid. Different denaturation, elution and clean-up conditions were tested. Quantification was carried out by gas chromatography equipped with electron capture detector (GC-ECD) or mass spectrometer (GC-MS). Recoveries of PCB congeners 28, 52, 101, 118, 138, 153 and 180 and OCPs HCB, beta-HCH, p,p'-DDE and p,p'-DDT at two spiking levels (n=8) varied from 57 to 120%, and intra-day relative standard deviation from 1 to 11%, both depending on spiking level and compound. Inter-day relative standard deviation was <15% in all cases. Limit of quantification (LOQ) for these PCBs ranged from 0.08 to 0.13 ng/ml and for these OCPs from 0.16 to 0.40 ng/ml. The optimized method was applied to the analysis of 1000 serum samples from different places of Spain.

Quantitative gas chromatography/time-of-flight mass spectrometry: a review

Time-of-flight (TOF) instruments have recently gained popularity in quantitative analyses. Normally, TOF mass spectrometers are used for accurate mass measurements for empirical formula verification. However, over the past decade, they have been used quantitatively as well. Because of the fast separations and narrow peaks that result from gas chromatography separations, scanning mass spectrometers are not ideal detectors. TOF mass spectrometers, however, have the ability to collect spectra at a faster rate. Two-dimensional gas chromatography has also been introduced to further resolve peaks from complex matrices. Two-dimensional gas chromatography results in a faster separation as well as narrower peaks. This paper reviews the methods currently in the literature for the quantitation of compounds using one- and two-dimensional gas chromatography and TOF mass spectrometry detection.

Rapid screening method for determination of PCDDs and PCDFs in fly ashes using GC-ion trap MS/MS based on cellular disruptor extraction

Identification and quantification of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in fly ashes from incinerator was carried out using capillary gas chromatography/tandem mass spectrometry (GC/MS/MS) with a low resolution ion trap mass spectrometer. Sample extraction was carried out in a cellular disruptor, in Soxhlet and in a conventional ultrasound for comparative purposes. Extraction with cellular disruptor was shown to be comparable to that obtained by the reference Soxhlet extraction, while low recoveries were observed with ultrasound. Hospital incinerator ashes, extracted by cellular disruptor and Soxhlet presented I-TEQ values for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans of 370 +/- 81 ng g(-1) and 533 +/- 55 ng g(-1), respectively, statistically equivalent according to the t-test.

Comprehensive two-dimensional gas chromatography with isotope dilution time-of-flight mass spectrometry for the measurement of dioxins and polychlorinated biphenyls in foodstuffs

A comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC x GC-TOF-MS) experimental setup was tested for the measurement of seven 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), ten 2,3,7,8-substituted polychlorinated dibenzofurans (PCDFs), four non-ortho-polychlorinated biphenyls (PCBs), eight mono-ortho-PCBs, and six indicator PCBs (Aroclor 1260) in foodstuff samples. A 40m RTX-500 (0.18mm I.D., 0.10 microm df) was used as the first dimension (1D) and a 1.5 m BPX-50 (0.10mm I.D., 0.10 microm df) as the second dimension (2D). The GC x GC chromatographic separation was completed in 45 min. Quantification was performed using 13C-label isotope dilution (ID). Isotope ratios of the selected quantification ions were checked against theoretical values prior to peak assignment and quantification. The dynamic working range spanned three orders of magnitude. The lowest detectable amount of 2,3,7,8-TCDD was 0.2 pg. Fish, pork, and milk samples were considered. On a congener basis, the GC x GC-ID-TOF-MS method was compared to the reference GC-ID high resolution mass spectrometry (HRMS) method and to the alternative GC-ID tandem-in-time quadrupole ion storage mass spectrometry (QIST-MS/MS). PCB levels ranged from low picogram (pg) to low nanogram (ng) per gram of sample and data compared very well between the different methods. For all matrices, PCDD/Fs were at a low pg level (0.05-3 pg) on a fresh weight basis. Although congener profiles were accurately described, RSDs of GC x GC-ID-TOF-MS and GC-QIST-MS/MS were much higher than for GC-ID-HRMS, especially for low level pork and milk. On a toxic equivalent (TEQ) basis, all methods, including the dioxin-responsive chemically activated luciferase gene expression (DR-CALUX) assay, produced similar responses. A cost comparison is also presented.

Recent advances in mass spectrometric measurement of dioxins

Past years, many efforts have been dedicated to the development of alternative analytical methods for the measurement of dioxins in various types of matrices. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are compounds that are present in samples at part-per-billion (ppb) or part-per-trillion (ppt) level. Their measurement requires the use of very sensitive analytical methods. Gas chromatography (GC) coupled to quadrupole ion storage mass spectrometry (QISTMS), fast GC (FGC) coupled to time-of-flight mass spectrometry (TOFMS) and comprehensive two-dimensional gas chromatography (GC x GC) coupled to TOFMS are the more promising tools challenging the reference GC high resolution mass spectrometry (HRMS) based on sector instruments. We report herein some of the advances we achieved in the past years in our laboratory on the development of alternative measurement methods for those compounds.

Improved separation of the 209 polychlorinated biphenyl congeners using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry

The separation of the 209 polychlorinated biphenyl (PCB) congeners has been studied using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS). Four column combinations based on thermally stable phases, DB-1/HT-8, DB-XLB/HT-8, DB-XLB/BPX-50, and HT-8/BPX-50, have been investigated. The HT-8/BPX-50 set produced the best separation. The distribution of the 100 to 150 ms wide peaks was highly structured in the chromatographic space and based on the degree of ortho-substitution within each separated homologue series. A total of 192 congeners were resolved in 146 min (1.3 analyte per min) using this column set. Eight coelutions involved 17 congeners. Among them, seven congeners were present in Aroclors at levels >1.0 wt.% (CBs 33, 47, 48, 95, 97, 163, 187). Except for CBs 47 and 48, none of the major constituents of commercial mixtures were coeluting. CB 138 was well separated from CBs 163 and 164 in the second dimension. For all column sets, CBs 20, 33, and 109 always coeluted with other PCBs. The 12 toxic dioxin-like congeners (CBs 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189), and the seven European Union marker PCBs (CBs 28, 52, 101, 118, 138, 153, 180) were separated from any interfering congeners. This was not the case for the other investigated column sets.