According to the Special Monitoring Applied Response Technologies (SMART) protocol developed by U.S. Coast Guard, NOAA, U.S. Environmental Protection Agency, when dispersants are used during oil spill response, the Unified Command needs to know whether the operation is effective in dispersing the oil. In-situ monitoring devices are needed for rapid collection of real-time data. In addition, oil slicks not dispersed may enter the coastal water and inland water system due to tides, winds and waves to form ‘oil in water’ emulsion. The spilled oil tends to dissolve slower in fresh water than in seawater environment. Along the north Gulf Coast, there are vast areas of marshes and wetlands with low salinity. This makes it more difficult for any oil in it to dissipate and dissolve. It is very important to keep monitoring the leaked oil in the coastal water system, especially wetlands, and gather valuable information not only for the evaluation of the impact of this oil spill disaster, but also for building up a database for future studies of the long term effect of spilled oil on the wetland ecosystem. According to SMART Protocol, the new generation instruments should meet the following requirements: in-situ monitoring, with the lower detection limit in 0.1–1 ppm and upper limit at least 100 ppm, easily deployable and portable, simplicity of use, high reliability and easier logistics, less maintenance and lower maintenance costs, and capable of being integrated with Windows operating systems and GPS.
This proposal targets to develop new instrument for improved detection associated with oil spills (Research Theme #4 of GoMRI). The goal is to develop a highly sensitive and portable instrument that can be used for in-situ detection of spilled oil. The device will have much higher sensitivity, lower cost, easier to operate and maintain, and with smaller size compared with the existing technologies. The applications of the instrument are not limited to oil detection and may also be used to measure any organic samples that can be measured in fluorescence detection principle.
The system will have a built-in sample extraction/pre-concentration function to eliminate external sample preparation kit. The oil enrichment is based on Solid Phase Extraction (SPE) and the oil detection is based on fluorescence detection principle. In its heart is a disposable CD-like microfluidic cartridge with a built-in oil pre-concentration unit. All the components on the cartridge will be passive with no power requirement. This micro-cartridge can be replaced easily. The micro-sized optical detection unit will be mounted under the microfluidic detection cartridge. All the active components such as UV light source, photo detector, power supplies, etc., are external to the cartridge and thus, belong to the permanent part of instrument. The cartridge can be easily interfaced to these active elements by placing it in a holder. And the cartridge is supposed to be inexpensively 3D-printed together with the solid phase adsorbent with no assembling requirement. It can therefore be disposable, and eliminates the problem of cleaning and contamination as in a permanently assembled fluidic device. We plan to first design and fabricate all the key components of the system, and build a small dimension bench-top model to demonstrate feasibility. Then in the next step, we will assemble and design a portable instrument from the tested bench-top components for the implementation of a beta model and start the field tests.
The key hypothesis in our proposed research is that fluorometry detection principle can still be effectively used with a dramatically reduced physical size of the measurement system. As the device size is scaled down in micro-size, both the sample volume and light intensity are significantly reduced in comparison with their conventional sized counterparts. To validate this hypothesis and prove the feasibility of the proposed microsystem, we have conducted preliminary study and obtained some very promising results. First, we have designed, fabricated, and tested a prototype micro-optic unit. The experimental results have found that the fluorescence signal is easily measurable when the oil density is reduced to below 10 ppm with no sample preconcentration. We also designed, fabricated a micro-sized liquid-to-liquid extraction unit for preconcentration of the oil-containing sample. The experiments have also proved that the prototype functions well in extracting oil contents from the sample fluid into the extractant fluid. This also validated the oil extraction can be achieved even if the physical size of the fluidic system is reduced to microscopic level. These results of the preliminary study have therefore validated our hypothesis and proved the feasibility of the proposed idea. To enhance the efficiency of the extraction, SPE is adopted instead of Liquid-Liquid (L-L) extraction in this proposal. We believe that significantly improved sensitivity well below 1ppm (even to 1ppb or lower) can be achieved with further study and optimal design for the optical detection system. Also, to get rid of the pumping system and minimize the device, our design will be built on a centrifugal platform. Based on the new technology, the new instrument should be much smaller than existing ones with significantly improved sensitivity.