Attenuated total reflection flow cell
Inventors
Assignees
United States Department of Commerce
Publication Number
US-9897541-B1
Publication Date
2018-02-20
Expiration Date
2037-01-20
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
An attenuated total reflection flow cell includes: a source prism; an internal reflection member that produces attenuated reflected light in response to attenuated reflectance of a source light; an exit prism that receives the attenuated reflected light from the internal reflection member; a flow member mechanically coupled to the internal reflection member to provide a flow of fluid to a surface of the internal reflection member.
Core Innovation
The invention disclosed is an attenuated total reflection (ATR) flow cell comprising a source prism that provides source light; an internal reflection member mechanically coupled to the source prism and disposed in optical communication such that it receives the source light, propagates it through multiple internal reflections between two surfaces, and produces attenuated reflected light in response to attenuated reflectance at the first surface. An exit prism is mechanically coupled to the internal reflection member to receive the attenuated reflected light. A flow member is mechanically coupled to the internal reflection member and provides a flow channel bounded by a channel wall such that fluid flows in contact with the first surface. The source light creates an evanescent wave at the first surface that interacts with the fluid to produce the attenuated reflected light, which is received and communicated by the exit prism.
The problem being addressed is the need for an effectively designed ATR flow cell that allows easy replacement of the internal reflection element, especially when irreversible alterations such as molecular adsorption occur on the internal reflection member. Traditional single crystal internal reflection elements are costly and require reconditioning. This invention provides a prism-coupled wafer of infrared transparent material as an internal reflection member. This configuration enables the wafer to be replaced without concern for returning to a pristine state, while the prisms for coupling infrared radiation are reusable indefinitely. Inclusion of a temperature-controlled platen adds rigidity needed to seal the flow channel to the wafer surface and enables temperature control, while polymeric materials for prism support allow fine optical alignment and localized pressure without fracturing the wafer.
Claims Coverage
The patent includes two independent claims directed to an attenuated total reflection flow cell and an attenuated total reflection flow system, covering optical, mechanical, and fluidic components and their interrelation.
Optical coupling and internal reflection configuration
A source prism mechanically coupled to an internal reflection member that receives source light and propagates it in multiple internal reflections between first and second surfaces, producing attenuated reflected light at the first surface. An exit prism mechanically coupled to the internal reflection member receives the attenuated reflected light.
Fluid flow integration with optical surfaces
A flow member mechanically coupled to the internal reflection member having a channel wall and flow channel arranged such that fluid flows in contact with the first surface where the evanescent wave from the source light interacts with the fluid to produce attenuated reflected light.
Flow direction relative to light propagation
The flow direction of fluid in the flow channel can be orthogonal or parallel, or set at any angle between 0° to 90°, relative to the direction of propagation of the source light within the internal reflection member.
Mechanical and thermal support components
A platen configured to receive and provide thermal contact to the internal reflection member, including optional heater elements controllable to selected temperatures, and prism pads supporting the source and exit prisms made from materials such as metal, polymer, glass, or ceramic. Clamps are used to hold and align these components rigidly.
Sealing and flow containment
A seal, such as an elastomeric gasket or O-ring, is interposed between the flow member and the first surface of the internal reflection member to constrain fluid flow to the flow channel during operation.
Complete system integration
An attenuated total reflection flow system comprising the flow cell, first and second flow lines in fluid communication with the flow channel, and optical components including mirrors to direct source light from a light source to the source prism and to direct attenuated reflected light from the exit prism to a detector.
Overall, the claims cover an ATR flow cell assembly comprising optical prisms and an internal reflection member with fluid flow over the reflection surface for spectroscopic measurements, incorporating mechanical features for sealing, thermal control, and component support, as well as an integrated system for directing light and fluid flow to facilitate analysis.
Stated Advantages
Provides an easily replaceable internal reflection element reducing cost and complexity associated with reconditioning irreversibly altered internal reflection surfaces.
Reuses prisms indefinitely, enhancing durability and cost-effectiveness of the system.
Incorporates temperature-controlled platen to provide rigidity needed to seal fluid flow and enable temperature regulation of the internal reflection member.
Use of polymeric prism supports enables fine optical alignment and localized pressure without fracturing the wafer.
Thin internal reflection members allow greater numbers of internal reflections enhancing signal-to-noise ratio and reducing material costs.
Prism coupling improves optical throughput and reduces need for fine adjustments when changing internal reflection members.
Flow channel coupling enables transient and dynamic measurements, including reaction monitoring with ease of reference measurements using an empty cell.
Documented Applications
Acquiring spectroscopic data of fluids by ATR spectroscopy, including infrared, visible, and ultraviolet spectra to monitor chemical reactions, adsorption, thermodynamics, fluorescence, chemiluminescence, phase changes, and isotopic exchange.
Studying surface reactions such as the formation of metal-organic frameworks (MOFs) in thin films, demonstrated by in situ monitoring of reaction kinetics and dynamics for conversion of zinc oxide thin films on silicon internal reflection members to hydroxy double salt intermediates and subsequently to HKUST-1 MOF thin films by flow of reagents.
Interested in licensing this patent?