Increasing analysis sensitivity of optical cells
The key objective of the CREAM project has been to develop a cartridge supporting a molecularly imprinted polymer assay that would allow on-site monitoring of antibiotic residues in milk. The developed cartridge consists of a sampling unit, a microreactor and an optical cell that will enable detection of analyte binding by fluorescence. For achieving increased performance researchers experimented with the optical instrument element and evaluated various optical detection schemes. Most commonly found micro-fabricated optical cells that are used in fluorescence studies present a disadvantage: their optical path is highly dependent on the substrate thickness. Thereby, the sample volumes they take are restricted to certain limits and this results to limited analysis sensitivity. Overcoming this problem, a new optical cell has been designed and optimised to meet the required assay specificity and sensitivity for the purposes of the CREAM cartridge. Formatted as an open channel array, the excitation/detection of this optical cell is based on the use of a different illumination pattern. While illumination usually take place normal to the cell plane, this cell is illuminated along its length, perpendicular to the cell plane. In this way, stray light effects on the final reading become minimal. Most importantly, the new arrangement allows the channel to specify the optical path, while the probed volume may be defined by the number of channels in the array. In addition, the channel-arrayed cell has a direct interface with the probed volume. This type of cell is suitably fitted for analytical cartridges based on capillary filling. A laboratory prototype is offered for technology transfer and industrial partners are sought for further specific developments.
