The hot, reducing nitrous oxide-acetylene flame has been applied to atomic absorption spectroscopy. Molybdenum in aqueous solution and steel sample solutions has been determined in such a flame. This has led to the indirect, sequential analyses of micro- gram amounts of both phosphorus and silicon by formation and extraction of their heteropolymolybdates into organic solvents followed by analysis of the molybdenum content by atomic absorption spectroscopy. Niobium and titanium have also been determined in a similar manner and the stoichiometry of their ternary heteropoly acids has been investigated. The selectivity of certain organic solvents in extracting phosphomolybdic acid has led to the titrimetric determination of microgram amounts of phosphate being re-examined. Microgram amounts of orthophosphate have also been determined by an indirect complexometric procedure.

Three simple protocols for the determination of the enantiomeric excess of chiral amines, hydroxylamines and diols have been developed utilising boronic acid templates. In Chapter 1 some of the existing methods for determining the enantiomeric excess of chiral substrates have been reviewed including the use of chiral solvating agents, chiral derivatization agents, chiral gas chromatography, chiral HPLC, circular dichroism, UV-visible spectroscopy and fluorescence spectroscopy. In Chapter 2 the previous work by the Bull-James group is discussed along with the cited uses of our three-component derivatization protocols for determining the enantiomeric excess of chiral amines and diols. The syntheses of a range of α-arylglycines are described and their optical purities determined by a simple 1H NMR derivatization protocol. In Chapter 3 the first reported chiral derivatization protocol for determining the enantiomeric excess of chiral hydroxylamines by 1H NMR spectroscopy has been developed by formation of nitrono-boronate ester complexes whose structures have been confirmed by X-ray crystallography. A range of chiral hydroxylamines have been prepared and the mechanism for the conversion of a chiral amine to its corresponding hydroxylamine has been proposed by analysis of the side product formed during the final reaction step converting an oxaziridine to the desired hydroxylamine. In Chapter 4 the Horeau Principle is discussed and its applications in the literature reviewed. A new derivatization protocol based on this principle has been developed employing an achiral boronic acid template to form diastereomeric dimeric boronate complexes by its reaction with two equivalents of a chiral diol. The scope and limitations of this protocol have been determined and molecular modelling has been used to explain the differences in diastereomeric resonances observed for the boronate complexes formed.

Anions are involved in fundamental processes in all living things. Recognition, transport and concentration control of anions such as chloride, phosphate and sulfate is carried out by biological systems on a perpetual basis. Fluoride, nitrate and pertechnetate are potentially dangerous contaminants that can gain access to our water systems by various means. Fluorosis, toxicity due to high levels of fluoride in drinking water, is a serious human health concern in many parts of the world Synthetic chemists seek to mimic nature’s level of sophistication in designing and making chemosensors capable of determining the concentration of a target anion in any medium. Beginning with a review of anion sensor chemistry with a particular focus on developments over the past 15 years, this thesis documents research into novel molecular sensors that target the differential sensing of fluoride and chloride anions. The design of these sensors has focussed on an optical signalling event based on electronic changes on binding but in addition, by virtue of a significant change in structural conformation. Fluorescent molecules have been utilised and as such, fluorescence emission changes investigated in the presence of a variety of anions. Results and Discussion I outlines our conformational model and discusses the design, synthesis and sensory behaviour of phenyl(boronates). UV, electrochemical, fluorescence and NMR techniques are brought together to elucidate the response of this class of molecule to various anions. One example designed to fit our proposed model shows interesting and unusual fluorescence quenching response to chloride anion. In addition, the synthesis of a related carbamate species and a range of oxygen bridged boron macrocycles are reported. Results and Discussion II discloses our approaches to more synthetically demanding constructs, obeying the model but trying to overcome the challenges met previously. An interesting, highly selective ratiomeric response to fluoride is observed with an isolated target molecule. Fluoride binding behaviour of a previously unexamined sp2 boron centre is examined.

Wastewater-based epidemiology (WBE) is an innovative tool that, unlike traditional epidemiological approaches, is capable of providing real-time profiling of community health and lifestyle along with emerging trends and changes in pattern usage of drugs in wastewater. By using human urinary excreted indicators, so-called “biomarkers”, WBE provides estimates at population level. Therefore, the choice and the evaluation of suitable biomarkers of exposure to drugs is of fundamental importance for the public health monitoring. Moreover, since many drugs are chiral, the investigation on enantiomeric profiling of chiral biomarkers provides a new dimension to WBE. To aid enantiomeric profiling in WBE, sensitive enantioselective methodologies are required. In this thesis, two novel multiresidue analytical methods based on chiral liquid chromatography coupled to mass spectrometry were developed and validated. The first method investigated the main human biomarkers for the detection of illicit drugs of abuse and potentially abused licit drugs. New biomarkers were investigated, such as mephedrone, PMA and all MDMA’s metabolites. Furthermore, a case study on mephedrone posed the basis for a novel approach towards biomarker selection in estimation of human exposure to chiral drugs with limited metabolism data. As a result, mephedrone was a suitable biomarker due to its stability in wastewater. In addition, some of its metabolites were also proposed as potential candidates for mephedrone use. The second method explored biomarkers of quinolones’ use, as they represent one class of antibiotics with rising concern in antibiotic resistance. The most comprehensive panel of quinolones’ biomarkers was considered for the first time in WBE studies. Both methodologies were applied to wastewaters from eight locations in Europe allowing the first pan-European studies on enantiomeric profiling of chiral biomarkers. Key findings of this research included: the detection of high mephedrone loads only in the UK, thus indicating human consumption; the detection of HMMA, a MDMA metabolite, as a suitable indicator of MDMA consumption and the determination of different synthetic production routes of methamphetamine across Europe. With regards to quinolones’ biomarkers, higher ofloxacin loads were found in Southern European cities along with differences in enantiomeric fraction with respect to Northern ones. Moreover, ofloxacin’s metabolites showed ofloxacin use and ulifloxacin was found as a result of prulifloxacin consumption. Therefore, enantiomeric profiling led to an understanding of: (i) new patterns of emerging drugs of abuse, (ii) changes in patterns of classical illicit drugs and (iii) quinolones with the verification of the origin of drug residue, potency of abused drug and its synthetic route and (iv) quinolones’ metabolic profiles. Moreover, the simultaneous determination of quinolones’ biomarkers in European samples allowed for the verification of spatial and temporal trends of quinolones’ use and the occurrence of their resistance genes. This proof-of-concept research will facilitate further advances in the WBE field.

No description available.

The capabilities of a new photoelectron spectrometer are characterised in the study of (C6F6)n– and (C6F6)I– clusters. The photoelectron spectrometer consists of a series of vacuum chambers that facilitate a molecular beam of gas-phase anions. These anions and clusters are generated at the point of intersection between an electron beam and the supersonic expansion produced by a high temperature Even-Lavie pulsed valve. The anions are extracted orthogonally and mass-separated in a Wiley-McLaren time-of-flight mass spectrometer. The analyte is addressed by a laser pulse produced by either a tuneable nanosecond OPO for one-photon frequency-resolved measurements or a femtosecond pump-probe regime for two-photon time-resolved measurements. The kinetic energy of the resulting photoelectrons are measured in a velocity-map imaging spectrometer. C6F6- is of interest due to the prediction that it ought to host a meta-stable binding mode of the excess electron known as a correlation-bound state (CBS). Similar to other non-valence binding modes, such as the dipole-bound state, this CBS is thought to act as a doorway state in the mechanism of low energy electron capture. The CBS is characterised by a large and diffuse orbital in which the excess electron is bound primarily through charge:induced-dipole interactions with the molecule’s valence orbital system. In the CBS, C6F6- is predicted to adopt a planar geometry like that of the neutral species, in contrast to the buckled geometry adopted when the excess electron occupies a valence orbital. Frequency- and time-resolved measurements of the anion were made in an effort to generate and observe the CBS. Initially, frequency resolved measurements of (C6F6)n– revealed a vertical detachment energy of 1.60 ± 0.07 eV for n = 1, increasing by 200 meV per additional cluster unit up to n = 5. The broad shape of the direct detachment peak confirms the disparity in geometry between the anion and neutral species. However, no evidence of the CBS was evident in these data. In subsequent explorations, an in-situ electron donor was employed to mimic the electron impact process. An I– ion was introduced to the neutral C6F6 molecule to produce clusters of (C6F6)I–. Frequency-resolved measurements of this cluster revealed a mechanism for electron loss below the threshold for the single-photon direct detachment process. This suggested the presence of a charge-transfer channel centred around hv = 3.3 eV. Time-resolved measurements of (C6F6)I– confirmed the presence of the charge-transfer state and revealed an instantaneous and coherent transfer of the electron onwards into the valence orbital system of the C6F6 molecule. This transfer of charge causes the molecule to vibrate as its geometry changes from planar to buckled. The oscillations observed in the photoelectron spectra are coherent and sinusoidal and have a frequency of 121 ± 2 cm−1. This compares very favourably to the frequency of 122 cm−1 calculated by time-dependent density functional theory for the bending mode of C6F6 along the coordinate between the planar and buckled geometries. I argue that this charge-transfer state exhibits the predicted characteristics of a CBS.

Mass Spectrometry (MS) is an important analytical tool in the identification and quantification of a wide range of samples, primarily because of its speed, sensitivity, selectivity and versatility in analysing, gases, solids and liquids. MS is an interdisciplinary analytical tool, impacting many areas of science from physics, through chemistry, to biology. However MS is mainly limited to laboratory settings due to the high vacuum requirement needed for ion generation and processing. The main theme of this work is the development of ionisation methods that enable ion generation and processing under ambient conditions in the open air outside of the laboratory for in-situ applications. To that end, it is also important that ions are generated and processed with little or no extensive sample preparation steps required. In this work the development of two ambient ionisation methods: desorption atmospheric pressure chemical ionisation (DAPCI) and paper spray (PS) ionisation and their application for in-situ MS analysis is demonstrated. A DAPCI handheld ion source version based on DAPCI was developed to ignite a corona discharge in air and operates for up to 12 h continuously using only 12 V battery. Both DAPCI and PS ambient ionisation methods were implemented for in-situ MS analysis and were used to detect trace amounts (< ng) of different classes of chemical compounds (i.e hydrocarbons, explosives corrosion inhibitors and metaldehyde in waters samples); this was achieved rapidly (i.e. less than 1 minute) with little or no sample preparation in the open air. Both ambient ionisation methods (i.e., DAPCI and PS) were used with either a commercial instrument or with a custom miniature mass spectrometer to identify and characterize traces amounts of petroleum oil hydrocarbons and additives (e.g. quaternary ammonium corrosion inhibitors), and water pollutants (e.g. metaldehyde) with high sensitivity and selectivity. The handheld DAPCI and PS methods were also applied to the in-situ direct analysis of explosives. Good performance was achieved with the miniaturised instrument giving detection limits within an order of magnitude to those achieved using a benchtop commercial instrument. The results reported in this thesis should be of importance to those interested in ambient ionisation mass spectrometry, miniature mass spectrometry, in-situ MS analysis, oilfield chemical analysis, homeland and border security agencies and environmental monitoring.

Airborne Volatile Organic Compounds are present throughout the atmosphere in a wide variety of species. An airborne Gas Chromatography/Mass Spectrometer was developed to measure these compounds in places otherwise inaccessible for ground- or ship-based instruments. The instrument was fitted to the UK FAAM BAe-146 Atmospheric Research Aircraft, and deployed on a number of campaigns. By the end of the project, the instrument was capable of making measurements that compared extremely well to other systems, meaning the proof of concept was successful. During the SAMBBA campaign, vertical profiles of biogenic and anthropogenic species were determined from the ground, up to 8000 m. These showed the extent to which different compounds (for example CO, benzene) were able to escape the planetary boundary layer and enter the free troposphere. Isoprene, however, with a much shorter lifetime of 0.5 hours, was primarily constrained to the boundary layer. Additionally, an analysis of biomass burning emissions was compared to those in literature. In particular the CO:VOC ratio was compared, with some species exhibiting very close comparisons, and others showing very different ratios leading to the conclusion that the CO:VOC ratio for some compounds is highly dependent on the species of trees. Measurements from the CAST campaign determined the extent to which naturally occurring halogenated species can travel from their source at the ocean surface, up to the lower stratosphere, affecting ozone levels. A comparison was also conducted with 3 other aircraft systems, for which the GC/MS was in good agreement. Finally, ights were conducted around the North Sea Oil and gas fields to determine background levels of compounds, in case of further leaks from natural gas extraction. Whilst the GC/MS could not identify specific plumes, calculations were performed to enhance the readings, showing very different levels of benzene emitted, which was dependent on the rig type.

The separated air-acetylene flame has been applied to atomic absorption spectroscopy. A long path variable sensitivity apparatus was developed which was stable, gave low background absorbances and enabled a number of elements to be determined with high sensitivity and reproducibility. The determination of mercury in the normal air-acetylene absorption flame by atomic-absorption spectroscopy was investigated and an explanation is offered for the variation in sensitivity which may be obtained under different circumstances. Beryllium has been determined by atomic thermal emission and atomic fluorescence spectroscopy in the separated nitrous oxideacetylene flame and the effects of a range of interferences investigated. An intense and stable microwave excited electrodeless discharge tube was developed as a source for the atomic fluorecence spectroscopy of beryllium. The atomic thermal emission spectra of the rare earths in the separated nitrous oxide-acetylene flame have been obtained and the possibility of determining the rare earths in this flame by atomic thermal emission spectroscopy investigated. A nitrous oxide-acetylene / air-acetylene burner of improved design suitable for separating or sheathing has been produced and tested. In the final. chanter some conclusions are drawn from the work which has been carried out and suggestions for increasing the sensitivity and .extending the scope of atomic spectral methods of analysis are made.

The chemical and physical properties of aromatic compounds are reviewed. Particular reference is made to the nuclear magnetic resonance interpretation of aromaticity,and several examples of its application are presented. An attempt is made to estimate the aromaticity of the five membered rings of indole,benzofuran and benzothiophene by means of nuclear magnetic resonance spectroscopy. The described method of calculation gives the aromaticity of these rings as 4496,30% and 61%, respectively,of that of benzene. The nuclear magnetic resonance spectra of the monomethylindenes,monomethylindoles,monomethylbenzo-furans and monomethylbenxothiophenes show that there is a small coupling (J-1c./sec) between the 3— and 7-proton: The cyclisation of beta-(m-toly1)-propionic acid and m-cresoxyacetyl chloride has been studied and both cyclisations have been found to yield a mixture of products. Each of these mixtures has been separated to give two ketones. Two of these ketones (7-methylindan-1-one and 4-methylcoumaran-3-one) have not been described previously. The unambiguous preparation of 4-,5-,6-and 7-methylindene is described.