Novel advances in lab on a chip instruments for in situ measurement of trace metals in marine waters

The oceans and marine waters of our planet play a major role in the biogeochemical cycles of a range of key metal elements that are linked with climatic variability and ocean productivity (e.g. Fe), and the health of which may be negatively impacted by a variety of anthropogenic inputs including metals. However, for us to understand the cycles and impacts of these metals there is a need for measurements of key chemical species at high frequency and over extended time periods. A range of in situ technologies are beginning to emerge that may have the potential to provide these data, including lab on a chip (LOAC) technologies that have the significant advantages of small size, and limited reagent and power requirements. However, even with recent developments in cell design and noise reduction, these LOAC systems do not have adequate sensitivity for determining the extremely low concentrations [pM to nM] of important metals in the vast majority of the waters in the ocean system. Here we propose a student develops a new and innovative approach to enhancing sensitivity through use of on chip chelating resin pre-concentration. The Centre for Marine Microsystems at the National Oceanography Centre, Southampton [NOCS] combines skills and scientific resources from across the University of Southampton with the Natural Environment Research Council sensor section at NOCS to provide an internationally known research group working at the leading edge of marine sensor technology [see www.soton.ac.uk/rmst]. This large group with interests extending from micro fluidics and micromechanical expertise, to studies on biofouling provides an excellent environment for the training of a research student in the proposed area, and will develop new applications of the NERC funded leading technology being developed to answer crucial environmental questions. Several marine in situ sensors from the group are already at technology readiness levels 4-6, and additional chemical analytical skills are provided through the PI Statham for the proposed project. Scaling down the resin pre-concentration procedures that are currently successfully used in bench-top flow injection analyser systems at the School of Ocean and Earth Science to LOAC dimensions is a challenging analytical and technological exercise. The phases in the project will initially involve the student getting up to speed with LOAC technology through lectures and hands on experience in the group, followed by the implementation of resin technology on a LOAC device. The work will at first use Mn as a test metal because of reduced complexity in speciation relative to e.g. Fe in natural waters, and the presence of a working picomolar bench system for analysing Mn in the SOES laboratory. After microfluidic characterisation of the resin-LOAC system, the selected resin bed will be tested for capacity, plus uptake and elution characteristics. Once these stages are complete, the new unit will be integrated into a new LOAC system that will combine the resin system and an existing colorimetric LOAC design. Laboratory testing will include temperatures and pressures typical of marine systems, and analytical figure so merit will be generated including testing of accuracy with certified reference materials. Field testing will use the NOCS instrumented jetty test site. Once the principals have been demonstrated for Mn a different resin will be applied to the determination of dissolved Fe in seawater. In addition to primary applications to NERC science (global carbon pump, further testing of Fe addition geo-engineering concepts, and environmental quality) such analytical devices will have applications to freshwater and potentially industrial systems where the use of element specific resins on LOAC devices may ber used to remove interfering elements prior to analysis, as well as pre-concentrating the analyte.