Ian D. McKelvie

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The inositol phosphates are a group of organic phosphorus compounds found widely in the natural environment, but that represent the greatest gap in our understanding of the global phosphorus cycle. They exist as inositols in various states of phosphorylation (bound to between one and six phosphate groups) and isomeric forms (e.g. myo, D-chiro, scyllo, neo),(More)
Phosphorus is an important macronutrient and the accurate determination of phosphorus species in environmental matrices such as natural waters and soils is essential for understanding the biogeochemical cycling of the element, studying its role in ecosystem health and monitoring compliance with legislation. This paper provides a critical review of sample(More)
This study reports the results from the analyses of a 30-year (1974-2004) river water quality monitoring dataset for NO x -N (NO₃-N + NO2-N), NH₄-N, PO₄-P and SiO₂-Si at the tidal limit of the River Tamar (SW England), an agriculturally dominated and sparsely populated catchment. Annual mean concentrations of NH4-N, PO₄-P and SiO₂-Si were similar to other(More)
A gas diffusion-flow injection system was developed for the determination of carbon dioxide in gaseous samples. The calibration was based on the use of either gaseous carbon dioxide or aqueous sodium carbonate standards. Gaseous carbon dioxide samples and gaseous or aqueous standards were injected directly into a donor stream of 1.0x10(-4)M H(2)SO(4). In(More)
The characterization of immobilized Escherichia coli alkaline phosphatase reactors used in flow injection analysis is reported for factors such as optimum pH, activity, ionic strength, product inhibition, and substrate specificity. The kinetics of the immobilized enzyme was studied, and mathematical descriptions were developed for the use of an immobilized(More)
This paper reviews the development and recent use of everyday communications and IT equipment (mobile phones, digital cameras, scanners, webcams, etc) as detection devices for colorimetric chemistries. Such devices can readily be applied for visible detection using reaction formats such as microfluidic paper based analytical devices (µPADs), indicator(More)
This review provides a critical assessment of knowledge regarding the determination of organic phosphorus (OP) and organic nitrogen (ON) in aquatic systems, with an emphasis on biogeochemical considerations and analytical challenges. A general background on organic phosphorus and organic nitrogen precedes a discussion of sample collection, extraction,(More)
Diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT) were applied in situ to obtain high spatial resolution dissolved reactive phosphorus (DRP) sediment porewater profiles in two lagoons of the Gippsland Lakes (SE Australia) during summer. Although the DRP depth profiles were different in each lake, highlighting the(More)
A low-cost disposable colorimetric microfluidic paper-based analytical device (μPAD) was developed for the determination of nitrite and nitrate. Nitrite is determined directly by the Griess reaction while nitrate is first reduced to nitrite in a hydrophilic channel of the μPAD with immobilized zinc microparticles. This μPAD is fabricated by a simple and(More)
A rapid method suitable for the determination of dissolved organic phosphorus (DOP) in soil leachates and runoff waters is presented. The flow injection (FI) manifold contains an in-line PTFE reaction coil wrapped around a low power UV lamp and is based on the spectrophotometric determination of dissolved reactive phosphorus (DRP) and mineralised DOP at 690(More)