Apparatus and method for acquiring an
infrared spectrum of a sample having or suspected to have an
amide I band, an
amide II band, an
amide III band, an amide A band, an OH stretching region or a combination thereof. A representative method includes providing a sample; providing an internal reflecting element (IRE) with a functionalized tip; contacting the sample with the IRE to form a sample-IRE interface; directing a beam of
infrared (IR)
radiation through the IRE under conditions such that the IR
radiation interacts with the sample-IRE interface once; recording a reflectance profile over a range of preselected frequencies, whereby an
infrared spectrum of the of a sample having or suspected of having an amide I band, an amide II band, an amide III band, an amide A band, an OH stretching region or a combination thereof, disposed in an
aqueous solution is acquired. Representative apparatus includes an internal reflecting element (IRE) comprising a reflection face located on the IRE at a region of intended contact between the IRE and a solublized sample; an infrared
radiation source for supplying an
evanescent wave of infrared radiation and directing the same from the outside of the IRE to the inside thereof so as to cause the infrared radiation to be incident on the reflection face, wherein the infrared radiation is reflected from the reflection face once; a sample
cell; a functionalized tip comprising a surface-immobilized probe that partially or completely fills the volume exposed to the
evanescent wave; and a
detector for detecting the once-reflected infrared radiation.