Gas chromatography coupled with ion trap mass spectrometry (GC-MS and GC-MS-MS) - for arson debris analysis

Gas chromatography - mass spectrometry (GC-MS) is an established instrumental technique used for the analysis of fire debris for accelerant detection. However, matrix problems, such as pyrolysis product interference, are still encountered. These interferences often lead to inconclusive interpretation of the chromatographic results. This study describes methods for analysing arson accelerants using gas chromatography coupled with ion trap mass spectrometry. The latter technique lends itself to both conventional (GC-MS) as well as tandem mass spectrometry (GC-MS-MS). Since petrol (gasoline) is one of the more common distillate blends used by arsonists, especially in South Africa, the identification of petrol in fire debris samples was investigated. In order to overcome pyrolysis product interference and improve detection selectivity of the aromatic hydrocarbons in petrol residues, tandem mass spectrometry was used in combination with capillary gas chromatography. The added parameter of the third dimension of selectivity proved to be superior to conventional GC-MS in obtaining characteristic aromatic hydrocarbon profiles for petrol without interference from pyrolysis artefacts.Dissertation (MSc (Applied Chemistry))--University of Pretoria, 2007.Chemistryunrestricte

Comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry for screening of organohalogenated compounds in cat hair

The coupling of comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry offers the best separation efficiency combined with accurate mass measurements over a wide mass range. The tremendous power of this screening tool is illustrated by trace qualitative screening analysis of organohalogenated compounds (OHCs) in pet cat hair. Tentative identification was supported by mass spectral database searches and elemental formula prediction from the experimentally determined accurate mass data. This screening approach resulted in the first tentative identification of pentabromoethylbenzene, decabromodiphenyl ethane, hexabromocyclododecane, trisbromoneopentyl alcohol, tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl)phosphate in the South African indoor environment. A total of seventy-two OHCs were identified in the samples and include known flame retardants, such as polybrominated diphenyl ethers, and legacy contaminants such as polychlorinated biphenyls and organochlorine, organophosphorous and pyrethroid pesticides. The results obtained from cat hair indicate that these pets are exposed to complex mixtures of OHCs and the detection of these compounds suggests that non-invasive cat hair samples can be used to model indoor exposure with reference to external deposition of OHCs present in the air and dust surrounding people. Toddlers share the same environment as pet cats and therefore also the same health risks

Establishing an alternative method for the quantitative analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans by comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry for developing countries

Comprehensive Gas Chromatography–Time-of-Flight Mass Spectrometry (GC×GC–TOFMS) methodology has been refined for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in samples with different matrices. This is specifically for application in developing countries where access to gas chromatography–high resolution mass spectrometry (GC–HRMS) and highly skilled personnel is limited. The method, using an Rxi-5 Sil MS column in the first dimension (D) coupled with an Rtx-200 column in the second dimension (D), was used to quantify PCDDs and PCDFs in different environmental sample matrices. The results were compared with those obtained usingGC–HRMSand good agreement was observed. The limit of detection (LOD) for the method (300 fg on column for spiked soil samples) was determined using an Rxi-XLB (1D) column coupled with an Rtx-200 column (D). Preliminary South African sample results are also discussed. Isomer specificity for different tetrachloro dibenzo-p-dioxins (TCDDs) and tetrachloro dibenzofurans (TCDFs) was investigated using a commercial standard. Adequate resolution was achieved. The method as described has great attraction for developing countries being both financially and operationally favourable.http://www.elsevier.com/locate/chrom

Experience in South Africa of combining bioanalysis and instrumental analysis of PCDD/Fs

We outline the experiences and the challenges of optimizing two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF-MS) in conjunction with the H4IIE-luc bioassay for analyzing polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the South African context. Investigating such alternative analytical methods can assist countries with developing economies to meet their obligations under the Stockholm Convention.Water Research Commission (WRC) of South Africa (K5/1561) and the South African/Norwegian Bilateral Agreement administered by the National Research Foundations (NRF) of South Africa and the Research Council of Norway (UID 64489).The authors also acknowledge support from a Discovery Grant from the National Science and Engineering Research Council of Canada (Project # 326415-07) and an instrumentation grant from the Canada Foundation for Infrastructure. Prof. Giesy was supported by the program of 2012 "High Level Foreign Experts" (#GDW20123200120) funded by the State Administration of Foreign Experts Affairs,the P.R. China to Nanjing University and the Einstein Professor Program of the Chinese Academy of Sciences. He was also supported by the Canada Research Chair program, an at large Chair Professorship at the Department of Biology and Chemistry and State Key Laboratory in Marine Pollution, City University of Hong Kong.http://www.elsevier.com/locate/trachb201

Analysis of transcription factors key for mouse pancreatic development establishes NKX2-2 and MNX1 mutations as causes of neonatal diabetes in man

notes: PMCID: PMC3887257This is a freely-available open access publication. Please cite the published version which is available via the DOI link in this record.Understanding transcriptional regulation of pancreatic development is required to advance current efforts in developing beta cell replacement therapies for patients with diabetes. Current knowledge of key transcriptional regulators has predominantly come from mouse studies, with rare, naturally occurring mutations establishing their relevance in man. This study used a combination of homozygosity analysis and Sanger sequencing in 37 consanguineous patients with permanent neonatal diabetes to search for homozygous mutations in 29 transcription factor genes important for murine pancreatic development. We identified homozygous mutations in 7 different genes in 11 unrelated patients and show that NKX2-2 and MNX1 are etiological genes for neonatal diabetes, thus confirming their key role in development of the human pancreas. The similar phenotype of the patients with recessive mutations and mice with inactivation of a transcription factor gene support there being common steps critical for pancreatic development and validate the use of rodent models for beta cell development.Wellcome TrustDiabetes UKEuropean Community’s Seventh Framework Programme (FP7/2007-2013

Trypanosoma vivax Infections: Pushing Ahead with Mouse Models for the Study of Nagana. I. Parasitological, Hematological and Pathological Parameters

African trypanosomiasis is a severe parasitic disease that affects both humans and livestock. Several different species may cause animal trypanosomosis and although Trypanosoma vivax (sub-genus Duttonella) is currently responsible for the vast majority of debilitating cases causing great economic hardship in West Africa and South America, little is known about its biology and interaction with its hosts. Relatively speaking, T. vivax has been more than neglected despite an urgent need to develop efficient control strategies. Some pioneering rodent models were developed to circumvent the difficulties of working with livestock, but disappointedly were for the most part discontinued decades ago. To gain more insight into the biology of T. vivax, its interactions with the host and consequently its pathogenesis, we have developed a number of reproducible murine models using a parasite isolate that is infectious for rodents. Firstly, we analyzed the parasitical characteristics of the infection using inbred and outbred mouse strains to compare the impact of host genetic background on the infection and on survival rates. Hematological studies showed that the infection gave rise to severe anemia, and histopathological investigations in various organs showed multifocal inflammatory infiltrates associated with extramedullary hematopoiesis in the liver, and cerebral edema. The models developed are consistent with field observations and pave the way for subsequent in-depth studies into the pathogenesis of T. vivax - trypanosomosis

Comprehensive two-dimensional chromatographic techniques for ultra-trace quantitative analysis of chlorinated dioxins in South Africa

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are toxic environmental pollutants formed as by-products of industrial and thermal processes. They are chlorinated compounds that have similar structures and chemical properties that were included in the original United Nations Environment Programme’s ‘dirty dozen’ and now form part of the Stockholm Convention (SC) on Persistent Organic Pollutants (POPs). As a signatory to the Stockholm Convention, South Africa has the obligation to undertake appropriate research, monitoring, and cooperation pertaining to POPs, and more particularly, PCDD/Fs. Currently there is no established PCDD/F laboratory in South Africa capable of these demanding measurements and alternative approaches must be considered that are more affordable, more robust and more user friendly for a developing economy. PCDD/Fs are highly toxic, causing a myriad of negative human health effects such as chloracne, carcinogenicity, hepatotoxicity, teratogenicity, endocrine disruption and alterations in neural development. The toxicity of PCDD/Fs is mediated through the aryl hydrocarbon receptor (AhR). PCDD/Fs bind to the AhR and elicit an AhR-mediated biochemical and toxic response. The in-depth information available on the mechanism of toxicity also allows for PCDD/Fs to be analysed using the AhR receptor mediated response in genetically modified cell lines. This led to the development of a bio-analytical screening technique using in vitro H4IIE-luc reporter gene bio-assay for AhR active compounds for the initial screening of PCDD/Fs in soil and sediment. The intension in this study was to develop an integrated approach to the analysis of PCDD/Fs in the South African environment, considering the associated cost as well as the available instrumentation, expertise and relevance within a developing economy. Historically, the quantitative confirmatory analysis of these compounds has been achieved by targeted analysis using gas chromatography coupled with high-resolution magnetic sector mass spectrometry instruments (GC-HRMS), the accepted benchmark technology used for determining the level of trace organic environmental contaminants such as PCDD/Fs. However, these methods are time consuming and expensive. Advances in technology have led to comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry (GC×GC-TOFMS) methodology that can be used for the analysis of PCDD/Fs in samples with different matrices. This approach is well suited for application in developing economies where access to GC-HRMS and highly skilled personnel is limited. This thesis describes the bio-analytical technique and the method development and analysis of the seventeen toxic PCDD/F congeners using GC×GC-TOFMS methodology. The technique provides the selectivity (added peak capacity of GC×GC) and the sensitivity (focusing effect of the modulator) needed to meet the requirements as mandated for analysis in US EPA Method 1613B. Extracted samples analysed on a GC-HRMS instrument, were re-analyzed using the low-resolution GC×GC-TOFMS instrument and the results confirmed using a high resolution TOF mass spectrometer (HRT). The quantitative results obtained compare well with those obtained using GC-HRMS. Because 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, although this information can be sample clean-up dependant. Preliminary validation of the GC×GC-TOFMS method is investigated using a certified reference material and real South African soil samples. The South African soil samples studied showed extremely high levels of PAHs, aliphatic hydrocarbons and sulphur. The organic content and matrix interference of South African soil samples (and the NIST standard reference material sediment; SRM 1944) provided significant challenges for the validation study. This study has shown that GC×GC-TOFMS provides a quick, convenient screen for numerous pollutant classes which may be present in environmental samples. Retrospective data mining of archived data (extraction dependant) is possible and has provided key information on other chlorinated and brominated contaminants present in South African waste, soil and sediment samples. NMISA now has a viable GC×GC-TOFMS dioxin analytical method for low level (ultra-trace) quantitative screening of chlorinated compounds that can be offered to South African analytical laboratories for routine dioxin analysis. The work is relevant scientifically and is a definitive contribution to the growing compilation of GC×GC methodology, providing efficient methods for this demanding environmental application.Thesis (PhD)--University of Pretoria, 2015.tm2015ChemistryPhDUnrestricte

Experience in South Africa of combining bioanalysis and instrumental analysis of PCDD/Fs

We outline the experiences and the challenges of optimizing two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF-MS) in conjunction with the H4IIE-luc bio-assay for analyzing polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the South African context. Investigating such alternative analytical methods can assist countries with developing economies to meet their obligations under the Stockholm Conventionhttp://www.journals.elsevier.com/trends-in-analytical-chemistry/http://www.sciencedirect.com/science/article/pii/S016599361300054Xdoi:10.1016/j.trac.2013.02.00

Critical review of the analysis of brominated flame retardants and their environmental levels in Africa

World-wide, the prevalence of brominated flame retardants (BFRs) is well documented for routine analysis of environmental and biological matrices. There is, however, limited information on these compounds in the African environment and insufficient information on the analytical approaches used to obtain data. This paper presents a review on BFR levels in the African environment and the various analytical methodologies specifically applied in Africa for polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls and alternative-BFRs. The analyses include liquid sample preparation using liquid-liquid and solid phase extraction and solid sample preparation involving Soxhlet extraction, with ultrasound-assisted extraction increasingly being applied. Instrumental detection techniques were limited to gas chromatography coupled with electron capture detector and electron impact ionisation with single quadrupole mass spectrometers. Information on congener profile prevalence in indoor dust, soil, aquatic environment (water, sediment, and aquatic organisms), eggs, wastewater treatment plant compartments, landfills (leachate and sediment) and breast milk are presented. Although PBDEs were inconsistently detected, contamination was reported for all investigated matrices in the African environment. The manifestation in remote regions indicates the ubiquitous prevalence and long-range transport of these compounds. Levels in sediment, and breast milk from some African countries were higher than reported for Asia and Europe. Due to limited data or non-detection of alternative-BFRs, it is unclear whether banned formulations were replaced in Africa. Most of the data reported for BFR levels in Africa were obtained in non-African laboratories or in South Africa and formed the basis for our discussion of reported contamination levels and related methodologies.In part by the National Research Foundation of South Africa (VU University Amsterdam – NRF Desmond Tutu doctoral scholarship) (Grant number 94075).http://www.elsevier.com/locate/chemospherehj2019Chemistr