title: Nanomolar detection with high sensitivity microfluidic absorption cells manufactured in tinted PMMA for chemical analysis.
abstract: We describe a novel, cost effective and simple technique for the manufacture of high sensitivity absorption cells for microfluidic analytical systems. The cells are made from tinted polymethyl methacrylate (PMMA) in which microfluidic channels are fabricated. Two windows (typically 250 μm thick, resulting in little optical power loss) are formed at either end of the channel through which light is coupled. Unwanted stray light from the emitter passes through a greater thickness of the tinted substrate (typically the length of the cell) and is preferentially absorbed. In effect, this creates a pin-hole configuration over the length of the absorption cell, providing improved performances (sensitivity, S/N ratios, baseline noise and limit of detection) when used as an absorption cell compared to clear substrates. The method is used to achieve a LOD of 20 nM with a colourimetric iron assay and a LOD of 0.22 milli-absorption units with a pH assay.
authors.affiliation: National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK. cfaf@noc.soton.ac.uk
authors.forename: Cedric F A
authors.initials: CF
authors.lastname: Floquet
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Sieben
authors.forename: Ambra
authors.initials: A
authors.lastname: Milani
authors.forename: Etienne P
authors.initials: EP
authors.lastname: Joly
authors.forename: Iain R G
authors.initials: IR
authors.lastname: Ogilvie
authors.forename: Hywel
authors.initials: H
authors.lastname: Morgan
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Mowlem
mesh_terms: D000042:Absorption; D007501:Iron / Q000032:analysis / Q000737:chemistry; D057230:Limit of Detection; D046210:Microfluidic Analytical Techniques / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D019904:Polymethyl Methacrylate / Q000737:chemistry*
chemical_list: D019904:Polymethyl Methacrylate; D007501:Iron