Liquid-phase and evanescent-wave cavity ring-down spectroscopy in analytical chemistry.
Due to its simplicity, versatility, and straightforward interpretation into absolute concentrations, molecular absorbance detection is widely used in liquid-phase analytical chemistry. Because this method is inherently less sensitive than zero-background techniques such as fluorescence detection, alternative, more sensitive measurement principles are being explored. This review discusses one of these: cavity ring-down spectroscopy (CRDS). Advantages of this technique include its long measurement pathlength and its insensitivity to light-source-intensity fluctuations. CRDS is already a well-established technique in the gas phase, so we focus on two new modes: liquid-phase CRDS and evanescent-wave (EW)-CRDS. Applications of liquid-phase CRDS in analytical chemistry focus on improving the sensitivity of absorbance detection in liquid chromatography. Currently, EW-CRDS is still in early stages: It is used to study basic interactions between molecules and silica surfaces. However, in the future this method may be used to develop, for instance, biosensors with high specificity.
van der Sneppen
L
L
Laser Center, Vrije Universiteit, Amsterdam 1081 HV, The Netherlands. wimu@nat.vu.nl
Ariese
F
F
Gooijer
C
C
Ubachs
W
W
D002853:Chromatography, Liquid / Q000295:instrumentation; D004867:Equipment Design; D055100:Optical Fibers; D013057:Spectrum Analysis / Q000295:instrumentation* / Q000379:methods / Q000639:trends