Extensive sample preparation can often limit the versatility, applicability and reproducibility of spectroscopic analytical methods, particularly with respect to in-situ and in-vivo analysis. Analytical instrumentation is now moving towards adaptation of conventional techniques to “preparation-free” sampling methods to circumvent these problems. Reflection techniques have been particularly well utilized in “preparation-free” probe techniques for infrared characterization. However, photothermal methods of detection have the added capability to discretely and nondestructively analyze sub-surface layers of a sample. This capability would be particularly useful for in-vivo measurements where depth of detection and sample morphology are of interest.
Here we will demonstrate the proof of principle experiments and propose a design for creating a mid-infrared probe using photothermal detection. This probe would require only sample contact to provide mid-infrared spectral measurements of surface and sub-surface layers with detection depth on the order of 0 - 50 microns. The key to this design is detection of the photothermal phenomenon in a solid medium above the surface of the sample using photothermal beam deflection (PTBD) and/or thermal lensing. This solid medium is suitable for attachment of fiber optics; creating a fixed alignment probe with flexible sampling capabilities and potential for significant miniaturization. This probe design could be utilized in a variety of ways, including in-situ process monitoring and in-vivo diagnostics.
Back to Analytical Chemistry I (General Session)
Back to The 56th Southeast Regional Meeting 2004 (November 10-13, 2004)