En raison de leur toxicité, les Hydrocarbures Aromatiques Polycycliques (HAP) font partie des polluants atmosphériques devant faire l'objet d'une surveillance (directive cadre européenne 96/62/CE du 27 septembre 1996). De par leurs propriétés physico-chimiques, certains de ces composés sont présents dans l'atmosphère simultanément en phases gazeuse et particulaire. Leur impact sanitaire et environnemental, différent selon la phase considérée, impose le prélèvement et l'analyse séparée des deux phases. Actuellement, la méthode la plus couramment utilisée pour l'échantillonnage simultané et séparé des phases gazeuse et particulaire est le préleveur à Haut-débit. Mais de nombreux auteurs ont montré que cette méthode engendrait des artefacts de prélèvement qui induisaient des erreurs dans l'estimation des concentrations. Ce travail de thèse répond à la nécessité de disposer d'un outil de prélèvement des HAP dépourvu d'artefact de prélèvement. Dans ce contexte, nos recherches ont porté sur la validation de la méthode de prélèvement par tube denuder multi-annulaire. Cette validation s'est articulée autour de tests en conditions contrôlées (banc à perméation, banc à rouleaux) afin d'évaluer l'impact des principaux paramètres susceptibles d'influer sur les performances du tube (température, humidité, concentration en HAP, taille des particules, conditions de prélèvement), et de prélèvements d'échantillons réels (atmosphériques) pour évaluer l'effet de la matrice environnementale. Elle a été complétée par une comparaison avec le préleveur conventionnel, à partir de prélèvements à l'émission d'un véhicule diesel (banc à rouleaux). Il ressort de l'ensemble de ces tests que le tube denuder multi-annulaire est une méthode adaptée au prélèvement simultané des HAP en phases gazeuse et particulaire, dans une gamme de conditions expérimentales couvrant largement le domaine de conditions généralement rencontrées dans l'environnement. Pour une étude plus précise du phénomène de distribution gaz-particule des HAP, le remplacement des préleveurs conventionnels par des systèmes «tube denuder» est ainsi fortement souhaitable.

Concentrations of diesel particulate matter (DPM) and polycyclic aromatic hydrocarbons (PAHs) in platinum mine environments are likely to be higher than in ambient air due to the use of diesel machinery in confined environments. PAHs may be present in gaseous or particulate phases each of which have different human health impacts due to their ultimate fate in the body. The sampling of both phases was made possible by means of small, portable denuder sampling devices consisting of two polydimethylsiloxane multi-channel traps connected in series and separated by a quartz fibre filter. Thermal desorption coupled with two dimensional gas chromatography with mass spectrometric detection (TD-GCxGC-ToFMS) was employed to analyse samples from three different platinum mines. The underground environments revealed that PAHs were predominantly found in the gaseous phase with naphthalene and mono-methylated derivatives being detected in the highest concentrations ranging from 0.15 – 8.73 μg.m-3. Similarly higher gas phase PAH loading was found in the Daspoort Tunnel. The particle bound PAHs underground were found in the highest concentrations at the Load Haul Dump (LHD) vehicle exhaust with dominance of fluoranthene and pyrene and concentrations ranged from 0.52-109.60 ng.m-3. This work highlighted the need to characterise both gaseous and particulate phases of PAHs in order to assess occupational exposure and demonstrated the successful application of these portable denuders in the mining environment. / Dissertation (MSc)--University of Pretoria, 2014. / tm2015 / Chemistry / MSc / Unrestricted

Isocyanates, aromatic-, aliphatic- and alkanolamines are commonly used in the industry today. Millions of workers in Europe are exposed. The most frequent health symptoms are respiratory and dermal disorder. Due to the health risk most of the compounds in this thesis are regulated by authorities and have occupational exposure limits (OELs). Consequently, reliable and robust air sampling methods are urgently needed. In this thesis dry samplers for isocyanates, aliphatic- and alkanolamines have been developed and evaluated. The isocyanate sampler is now a commercial product (ASSET EZ4-NCP Dry Sampler, Supelco). The samplers were based on a denuder with a filter in series. The denuder and filter were impregnated with di-n-butylamine for the isocyanate sampler and with sulphuric acid for the aliphatic- and alkanolamine sampler. The robustness of the dry samplers was extensively evaluated. This was performed in a climate chamber containing a controlled atmosphere of the studied compounds. New methods based on hydrophilic interaction liquid chromatography (HILIC) coupled with tandem mass spectrometry (MSMS) were developed for determination of aromatic-, aliphatic- and alkanolamines in aqueous solutions. Isocyanates were determined by reversed-phase liquid chromatography MSMS. HILIC in combination with MS is a most powerful system, and highly sensitive determinations, several orders of magnitude below the OELs, of polar compounds present in the work environment can be accomplished. The selected samplers enable sampling during short sampling times and for whole work shifts. The samplers can be stored for months before and after sampling. The performance of the samplers was unaffected by variation in temperature, humidity, flow-rate and pre- and post-sampling of ambient air. Sampling for the compounds studied is now greatly simplified, and assessment of the work environment is facilitated. / <p>At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Epub ahead of print; Papers 3-5: Manuscripts</p>

Extraction is required to separate and concentrate trace level analytes from the sample matrix prior to gas chromatography (GC). Classical extraction procedures utilise large amounts of hazardous solvents, generate waste, and sensitivity limitations are associated with the injection of microlitre amounts of the final solvent extract. In response to real world challenges, and to overcome the problems associated with solvent extraction, novel silicone rubber (polydimethylsiloxane (PDMS)) samplers were developed for solvent free enrichment of trace level analytes from indoor air, contaminated soil, desert soil, ultra high temperature (UHT) milk and Pinotage wine. Versatile PDMS samplers as a loop, a multichannel trap, or a denuder for trace environmental forensics, geochemical and aroma investigations are presented. A unique off-line multidimensional GC approach involving heart-cut gas chromatographic fraction collection is described, as is off-line olfactory assessment of recombined heart-cuts for synergistic odour effects. PDMS loop samplers were used for the extraction of DDT (1,1,1- trichloro-2,2-bis(p-chlorophenyl)ethane) and its associated environmental pollutants from soil samples. Miniature denuder samplers accomplished separate concentration of vapour phase and of particulate phase fractions of DDT and its associated environmental pollutants from indoor air, in a single step. Ratios of airborne p,p’-DDD/p,p’-DDT and of o,p’-DDT/p,p’-DDT are unusual and do not match the ideal certified ingredient composition required of commercial DDT. Results suggest that commercial DDT used for indoor residual spraying may have been compromised with regards to insecticidal efficacy, demonstrating the power of this new environmental forensics tool. Multichannel PDMS trap samplers were used in a unique heart-cut multidimensional GC approach for off-line enantiomeric separation of o,p’-DDT and o,p’-DDD in air and soil. This alternative multidimensional method is compared to the complementary technique of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GCxGC-TOFMS). PDMS loop samplers were also employed for the solvent free extraction of hydrocarbons from desert soil to investigate, for the first time, a possible geochemical origin of the enigmatic fairy circles of Namibia. It is proposed that microseepages of natural gas and low volatility hydrocarbons are expressed at the surface as a geobotanical anomaly of barren circles and circles of altered vegetation. Multichannel PDMS trap samplers were utilised for sampling of the headspace of UHT milk and of Pinotage wine, and to study off-line, using a portable olfactometer, synergistic effects between recombined heart-cut aroma compounds. Olfactory results show that a synergistic combination of 2- heptanone and 2-nonanone was responsible for a pungent cheese-like odour in UHT milk, while a synergistic combination of furfural and 2-furanmethanol was responsible for a roast coffee bean-like odour in coffee style Pinotage wine. The small, low cost samplers are quick and easy to assemble and they fit commercial thermal desorber systems. The PDMS samplers are reusable. Solvent extraction of the sampling materials, extract clean-up and pre-concentration are not required. Thus, potential loss of analyte, introduction of contaminants and waste disposal are minimised. Solvent free thermal desorption permits transfer of the entire sample mass to the cooled injection system (CIS) inlet of a GC resulting in greater sensitivity when compared to injection of microlitre amounts of a solvent extract. This allowed for sampling of smaller sized soil samples, shorter air sampling times and lower air sampling flow rates when compared to solvent based methods. / Thesis (PhD)--University of Pretoria, 2013. / Chemistry / unrestricted

<p>This thesis presents methods for air sampling and determination of isocyanates, amines, aminoisocyanates and anhydrides. These organic compounds are generated during thermal degradation of polymers such as polyurethane (PUR) or epoxy.</p><p>Isocyanates, amines and anhydrides are airway irritants known to cause occupational asthma. Some of the compounds are listed as human carcinogens. Many workers are exposed.</p><p>Isocyanates and anhydrides are reactive and needs to be immediately derivatized during sampling. Methods have been developed for determination of airborne isocyanates, aminoisocyanates and anhydrides using di-n-butylamine (DBA) as reagent to form stabile urea derivatives or amide derivatives. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enabled detection limits as low as 10 attomoles. A nitrogen-selective LC-detector enabled quantification of DBA-derivatives in reference solutions. </p><p>A novel sampler is presented. The sampler consists of a denuder in series with a three-stage cascade impactor and an end filter. The sampler made it possible to reveal the distribution of isocyanates between gas and different particle size fractions. During thermal degradation of PUR, isocyanates were associated to particle size fractions (<1 µm) that may penetrate to the lower airways. The distribution during 8 minutes changes noticeably. Aromatic isocyanates become associated to small particles (<1 µm). As a reference method, air-sampling was performed using an impinger filled with di-n-butylamine (DBA) in toluene, connected in series with a glass fiber filter. There was a good agreement between the denuder-impactor sampler and the reference method.</p>

This thesis presents methods for air sampling and determination of isocyanates, amines, aminoisocyanates and anhydrides. These organic compounds are generated during thermal degradation of polymers such as polyurethane (PUR) or epoxy. Isocyanates, amines and anhydrides are airway irritants known to cause occupational asthma. Some of the compounds are listed as human carcinogens. Many workers are exposed. Isocyanates and anhydrides are reactive and needs to be immediately derivatized during sampling. Methods have been developed for determination of airborne isocyanates, aminoisocyanates and anhydrides using di-n-butylamine (DBA) as reagent to form stabile urea derivatives or amide derivatives. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enabled detection limits as low as 10 attomoles. A nitrogen-selective LC-detector enabled quantification of DBA-derivatives in reference solutions. A novel sampler is presented. The sampler consists of a denuder in series with a three-stage cascade impactor and an end filter. The sampler made it possible to reveal the distribution of isocyanates between gas and different particle size fractions. During thermal degradation of PUR, isocyanates were associated to particle size fractions (&lt;1 µm) that may penetrate to the lower airways. The distribution during 8 minutes changes noticeably. Aromatic isocyanates become associated to small particles (&lt;1 µm). As a reference method, air-sampling was performed using an impinger filled with di-n-butylamine (DBA) in toluene, connected in series with a glass fiber filter. There was a good agreement between the denuder-impactor sampler and the reference method.