Libraries of peptide based chiral stationary phases (CSPs), using silica-supports, were developed. The CSPs were packed into columns and tested for their ability to resolve racemates using a range of test analytes. The research focused on varying the CSP end group and results show that the most important was 3,5-dinitrobenzoyl. Furthermore, CSPs were developed that used 3,5-dinitrophenylalanine; an amino acid variant of the 3,5-dinitrobenzoyl group, in the peptide core. However, these CSP were found to be unsuccessful in separating the test analytes. Protein chiral stationary phase ligands were screened with a surface plasmon resonance biosensor (Biacore S51), using pharmaceutical enantiomers as analytes, to obtain binding characteristics. Furthermore, these results correlated well with the analogous screenings carried out on HPLC. A reciprocally designed CSP based on a single enantiomer of anthryl ethanol was synthesised, the key step involved the use of Sharpless asymmetric dihydroxylation which incorporated optical character into the molecule. The enantiomer was attached to a silica support and used as a CSP to separate peptide racemates.

No description available.

No description available.

Determination of low levels of chemicals unintentionally present in foods (trace contaminants) often requires extensive wet chemistry extraction and clean-up regimes prior to instrumental analysis and this is usually the bottleneck in analysis. In order to determine if levels pose a human health risk, rapid reliable methods are required that can unequivocally identify and quantify contaminants at trace levels. In particular, current methods for targeted food taint analysis have long extraction times and rapid screening methods such as direct headspace, do not provide the sensitivity required. In order to address the issues raised above, this study set out to review all aspects of sample preparation and the applicability of each technique for the determination of trace organic contaminants in foods. Following the review, solid-phase dynamic extraction (SPDE) was evaluated for the determination of example food contaminants furan and the BTEX compounds (benzene, toluene, ethyl benzene and 0, rn, and p-xylene). Stir bar sorptive extraction (SBSE) was also evaluated for the determination of furan, benzene and toluene. A SBSE method for the determination of furan in food and beverages was developed which gave the advantage of extraction at ambient temperature, (thus minimising potential formation) and was comparable to direct static headspace in performance and sensitivity. The use of SBSE was then evaluated for use as a generic screening method for compounds known to cause taints in foods. Twenty example compounds were chosen based on previously reported taints from a range of origins and included those most commonly investigated (such as halogenated phenols and anisoles). The optimised SBSE method was compared to the more established techniques, direct static headspace and steam distillation extraction using Likens Nickerson apparatus. The SBSE method provided an increase in sensitivity for most compounds and further improvements were demonstrated for more targeted analysis, using a GC-MS, GC-MS/MS and GC-HRMS instrumentation.

Firstly, a detailed study of the higher Rydberg states of C<SUB>6</SUB>H<SUB>6</SUB> and C<SUB>6</SUB>D<SUB>6</SUB> was performed using mass-resolved polarisation-dependent (2+1) REMPI spectroscopy. Three long series of gerade Rydberg states (two <I>nd</I> and possibly one <I>ng</I>) converging on the first ionisation energy, previously observed up to <I>n</I>=8, were extended up to <I>n</I>=30. By scanning the two-photon energy up to the ionisation limit, coherent two-photon ZEKE-PFI spectra of the ionic states of benzene-<I>h</I><SUB>6</SUB> and -<I>d</I><SUB>6</SUB> were obtained for the first time. The vibrational structure in the ZEKE spectrum is essentially the same as in the (2+1) REMPI spectra of Rydberg states but different from the (1+1') ZEKE spectrum reported previously. Substitution effects and the influence of lowering the symmetry on the Rydberg states were also investigated by comparing studies of C<SUB>6</SUB>H<SUB>5</SUB>F, C<SUB>6</SUB>H<SUB>5</SUB>Cl, <I>p</I>-C<SUB>6</SUB>H<SUB>4</SUB>F<SUB>2</SUB> and <I>o</I>-C<SUB>6</SUB>H<SUB>4</SUB>F<SUB>2 </SUB>molecules. Second, the Rydberg and ionic states of CF<SUB>3</SUB>I have been studied using both REMPI and zero kinetic energy pulse-field ionisation (ZEKE-PFI) photoelectron spectroscopy. The ground state of the ion was characterized using coherent two-photon (one-colour) ZEKE-PFI spectroscopy. The 6p Rydberg states were studied using two-photon REMPI spectroscopy with linear and circular polarised light. The strongest members with Ω=2 were identified and used as resonant intermediates in two-colour (2+1') ZEKE-PFI experiments, which allowed the unambiguous assignment of the majority of the vibrational structure of the intermediate states. Third, multiphoton pathways to the lowest cluster of ion-pair states of ICl and I<SUB>2</SUB>, at energies close to the dissociation limit, are presented. These very high vibrational levels are detected in the anion (Cl<SUP>-</SUP> and I<SUP>-</SUP>) or cation (I<SUP>+</SUP>) channel by pulsed field ionisation. Using a variable time delay before field ionisation, ion pair states up to 50 cm<SUP>-1</SUP> below the dissociation limit are observed to survive for at least 2 μs, indicating a stabilisation process analogous to that operating in high Rydberg electronic states. The analogy between these stabilised ion-pair states and ZEKE (zero electron kinetic energy) states suggests calling them ZIKE (zero ion kinetic energy) states. The atomic ion yield signal is highly structured both above and below the free ion threshold, indicating the role of doorway states which are coupled to the dense ion-pair vibrational manifold near dissociation. This coupling appears to be very efficient and competes successfully with radiative decay and further up-pumping that would result in ionisation. One difference with ZEKE spectroscopy is that these initially prepared states have to undergo both an electronic transition as well as a large angular momentum change, in order to be stabilised. Fourth, molecular photofragment spectroscopy has been used to obtain new insight into the ultraviolet photodissociation of ozone. The formation of O<SUB>2</SUB>(b<SUP>1</SUP>Σ<SUP>+</SUP><SUB>g</SUB>) following absorption in the Huggins band (335-352 nm) of O<SUB>3</SUB> has been observed for the first time. The nascent O<SUB>2</SUB>(b<SUP>1</SUP>Σ<SUP>+</SUP><SUB>g</SUB>) photofragment was detected using two-colour resonance enhanced multiphoton ionisation (REMPI), and the 3sσ<SUB>g</SUB><SUP>1</SUP>Π<SUB>g</SUB> Rydberg state as the resonant intermediate state. Finally, a new VUV generation technique (laser induced plasma), which may be used for spectroscopic studies, has been characterised. Some preliminary results using this new VUV generation source for single photon ionisation and ion-pair production studies of polyatomic molecules (CH<SUB>3</SUB>Br and CH<SUB>3</SUB>I) have been obtained. In addition, high resolution ion-pair formation from CH<SUB>3</SUB>Br using coherent VUV laser radiation generated by four wave mixing has been recorded in both CH<SUB>3</SUB><SUP>+</SUP> and Br<SUP>-</SUP> channels.

No description available.

The preparation of two new [18]aneS₄N₂ macrocycles with conjugated links to redox-active Co centres has been achieved [(CpCo)₂S₄N₂ and (CpCo)S₄N₂ via reaction of an [18aneS₄N₂ bisthione macrocycle with CpCoLL, LL = COD or (CO)₂. Optimisation of this reaction had lead to a high yielding and selective route to the ligand containing one Co centre. The characterisation of these complexes is described in detail and includes a study of the spectro-electrochemical, electrochemical, EPR and UV/Vis spectroscopic data. The second section of this thesis concentrates on complexation studies of these redox-active cobalt macrocycles with a variety of transition metal ions. The metal ions are a mixture of late transition metal and heavy metal ions and include possible pollutant species present within aqueous environmental systems. They include, Ag^I, Fe^II, Co^II, Ni^II, Cu^I, Cu^II, Pb^II, Cd^II, Hg^II, and Sn^II. The studies was carried out in variety of solvent systems and complexations were followed by modifications in electrochemical behaviour and UV/Vis spectroscopy. Strong interactions were observed between the Co centre and the guest metal ion in the macrocycle in several cases and encouraging results are reported indicating the use of these systems in Ion Sensing. In particular the complexation study carried out with Ag^I and Ni^II proved to be the most significant. A route to the method of complexation of the ions, Ag^I, Fe^II, Co^II, Ni^II, Cu^I, and Cu^II is proposed with a suggestion for an alternative pathway for the complexation of the heavier metals, Sn^II, Pb^II, Hg^II and Cd^II is also given.

The first project describes research into elucidating a new and more cost-effective method of measuring the setting rate of cement than time resolved X-ray diffraction detection of cement mineralogy. The solution arrived at was to monitor the composition of the fluid phase by ICP-AES and applied thermodynamic modelling. By using this method, it was possible to detect the Ettringite to Monosulphate phase shift, an important kinetic point in the setting of cement. The second section describes a project where the aim was to find a method of determining the source region of a group of cannabis resin samples ranging form 20 to 1 year old. The resin was analysed by stable isotope mass spectroscopy for its d²H, d¹³C and d¹⁵N isotope ratios, which revealed that in all likelihood, the samples came from a single country. Additionally, the relative abundances of cannabinoids extracted from the resin were analysed by GC-MS and shoed that there may have been some changes in the biosynthesis pathway of the main psychoactive cannabinoid, tetrahydrocannabinol, in this growth area sometime in the past 4 years. The projects cover an extremely large analytical range: the first project used spectroscopy to answer a physical/inorganic chemistry question for an engineering application whereas the second project used mass spectrometry to answer a geographic/biochemical question for forensic scientists. Combined, these projects have shown some of the breadth of skills than an instrumental analytical chemist must have in the modern world.

Mercapturic acids are urinary metabolites which signal exposure to genotoxic compounds. Carefully designed hapten-protein conjugates and a judicious screening strategy has enabled the generation of compound and class-specific antibodies which bind mercapturic acids. S-phenylmercapuric acid (S-PMA) is a highly specific and sensitive marker of benzene exposure. A monoclonal antibody reactive with S-PMA has been generated. The immobilised antibody retains immunoreactivity and can be used to enrich S-PMA from the urine of benzene exposed workers. The performance of the immunoaffinity column has been validated by comparison with data obtained from GC/MS analysis of urine from benzene exposed workers (range 12-168ug/1. corr. coeff. 0.98, n=23). Furthermore immunoaffinity chromatography facilitates the quantitative determination of urinary S-PMA by HPLC. Bioconcentration of S-PMA from the urine of benzene exposed workers has permitted the quantification of S-PMA by HPLC at 8 hour Time Weighted Average exposures of around 1ppm. Monoclonal antibodies to low molecular weight mercapturic acids (eg. S-(2-hydroxyethyl)mercapturic acid) were generally of too low affinity for practical application. As an alternative approach antibodies to adducted protein were investigated. Antibody 4D3 binds the adducted N-terminal heptapeptide released from the alpha-chain of haemoglobin by trypsin hydrolysis. Initial studies suggest antibody 4D3 can bind the adducted heptapeptide in whole haemoglobin. This may facilitate the determination of adducted haemoglobin in biomonitoring studies.

A nebulized flame ionization detector interfaced with LC was examined and found to be more versatile in applications than common LC detectors, such as UV, RID, ELSD and CAD. The technique can be used for both volatile and non-volatile analytes. It is compatible with gradient elution and can be used for the analysis of non chromophore-possessing analytes. The calibration plots of non-volatile analytes were linear in contrast to other aerosol-based detectors, such as ELSD and CAD. The technique was examined in three consecutive stages; optimization of the FID, testing the response patterns of analytes (volatile and non-volatile) and applications to the analysis of compounds of diverse functional groups. The optimum conditions for the operation of the FID were: hydrogen, 157 ml/min; nitrogen, 250 ml/min; air, 654 ml/min; spray chamber internal diameter, 40 mm, collector internal diameter, 4mm and eluent (water), 1 ml/min. The calibration plots of all volatile analytes were linear while those of the non-volatile analytes were linear only when anions (in the form of sulfuric acid, nitric acid, hydrochloric acid, orthophosphoric acid, sodium sulphate and ammonium sulphate) were added to the eluent The separations of diverse analytes (alcohols, aldehydes, ketones, amines, amino acids, carboxylic acids and sugars) gave detection limits in the low μg range.