ORCID Profile
0000-0002-9914-3276
Current Organisation
Queensland University of Technology (QUT)
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Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.WATRES.2013.05.034
Abstract: Ultraviolet (UV) irradiation is commonly employed for water treatment in swimming pools to complement conventional chlorination, and to reduce the concentration of inorganic chloramine compounds. The approach of combining UV irradiation and chlorination has the potential to improve water quality, as defined by microbial composition. However, relatively little is known about the effects of this process on water chemistry. To address this issue, experiments were conducted to examine the effects of sequential UV254 irradiation/chlorination, as will occur in recirculating system of swimming pools, on disinfection byproduct (DBP) formation. Creatinine, which is present in human sweat and urine, was selected as the target precursor for these experiments. Enhanced formation of dichloromethylamine (CH3NCl2) and inorganic chloramines was observed to result from post-chlorination of UV-irradiated s les. Chlorocreatinine was found to be more sensitive to UV254 irradiation than creatinine UV254 irradiation of chlorocreatinine resulted in opening of the ring structure, thereby yielding a series of intermediates that were more susceptible to free chlorine attack than their parent compound. The quantum yields for photodegradation of creatinine and chlorocreatinine at 254 nm were estimated at 0.011 ± 0.002 mol/E and 0.144 ± 0.011 mol/E, respectively. The N-Cl bond was found to be common to UV-sensitive chlorinated compounds (e.g., inorganic chloramines, CH3NCl2, and chlorocreatinine) compounds that were less susceptible to UV-based attack generally lacked the N-Cl bond. This suggested that the N-Cl bond is susceptible to UV254 irradiation, and cleavage of the N-Cl bond appears to open or promote reaction pathways that involve free chlorine, thereby enhancing formation of some DBPs and promoting loss of free chlorine. Proposed reaction mechanisms to describe this behavior based on creatinine as a precursor are presented.
Publisher: Wiley
Date: 16-12-2011
Abstract: The reactivity of 3-hydroxy-2,4,6-tridehydropyridinium cation was found to be drastically different from the reactivity of 2,4,6-tridehydropyridinium cation. While the latter triradical reacts with tetrahydrofuran, dimethyl disulfide and ally iodide via three consecutive atom or group abstractions, the former triradical exhibits this behavior only with tetrahydrofuran. Only a single atom or group abstraction was observed for the 3-hydroxy-2,4,6-tridehydropyridinium cation upon interaction with dimethyl disulfide and allyl iodide. This change in reactivity is caused by the hydroxyl group that strengthens the interactions between the two radical sites adjacent to it, thus reducing their reactivity. This explanation is supported by the observation of similar behavior for related biradicals.
Publisher: Wiley
Date: 16-03-2015
DOI: 10.1002/RCM.7154
Abstract: N-Monosubstituted hydroxylamines correspond to an important class of metabolites for many bioactive molecules. In this study, a tandem mass spectrometric method based on ion/molecule reactions was developed for the identification of compounds with the N-monosubstituted hydroxylamino functionality. The diagnostic ion/molecule reaction occurs between protonated analytes with 2-methoxypropene (MOP) inside a linear quadrupole ion trap mass spectrometer. Most protonated compounds with N-monosubstituted and disubstituted hydroxylamino and oxime functional groups react with MOP via proton transfer and formation of a stable adduct in a linear quadrupole ion trap mass spectrometer. However, only protonated compounds with N-monosubstituted hydroxylamino groups form the characteristic MOP adduct-MeOH product. Possible mechanisms of this reaction are discussed. A method based on functional group-selective ion/molecule reactions in a linear quadrupole ion trap mass spectrometer has been demonstrated to allow the identification of protonated compounds with the N-monosubstituted hydroxylamino functionality. Only N-monosubstituted hydroxylamines react with MOP via formation of an adduct that has eliminated methanol.
Publisher: American Chemical Society (ACS)
Date: 17-03-2014
DOI: 10.1021/JO402645A
Abstract: A tandem mass spectrometric method is presented for the rapid identification of drug metabolites that contain the sulfone functional group. This method is based on a gas-phase ion/molecule reaction of protonated sulfone analytes with trimethyl borate (TMB) that yields a diagnostic product ion, adduct-Me2O, at high reaction efficiency. A variety of compounds with different functional groups, such as sulfoxides, hydroxylamines, N-oxides, anilines, phenol, an aliphatic amine, and an aliphatic alcohol, were examined to probe the selectivity of this reaction. Except for protonated sulfones, most of the protonated compounds react very slowly or not at all with TMB. Most importantly, none of them give the adduct-Me2O product. A mechanism that explains the observed selectivity is proposed for the diagnostic reaction and is supported by quantum chemical calculations. The reaction was tested with the anti-inflammatory drug sulindac and its metabolite, sulindac sulfone, which were readily distinguished. The presence of other functionalities in addition to sulfone was found not to influence the diagnostic reactivity.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4AN00677A
Abstract: A mass spectrometric method utilizing gas-phase ion/molecule reactions of 2-methoxypropene (MOP) has been developed for the identification of the sulfoxide functionality in protonated analytes in a LQIT mass spectrometer.
Publisher: American Chemical Society (ACS)
Date: 29-08-2013
DOI: 10.1021/CR400121W
No related grants have been discovered for Peggy Williams.