Reflectometric interference

Figure 4. Reflectometric interference spectroscopy (RIFS) caused by constructive and destructive superposition of two partial beams being reflected at the two interfaces of a thin layer (300 nm - some pm), shift of the interference spectrum caused by a change in the optical thickness.

In the following, the application of these concepts is shown both for reffactometric and reflectometric measurements using Mach-Zehnder interferometers and reflectometric interference spectroscopy. 

Reflectometric interference spectroscopy can also be used to easily determine various interactions between analytes and polymer films27. A typical application is given in Figure 14 for a homologuous series of alcohols29. 

Figure 17. Structure affinity relationship measurement using reflectometric interference spectroscopy of atrazine versus an antibody in water. A variety of derivatives of triazines are measured at a number of concentrations to obtain affinity constants.

Because of the more simple and robust technique of reflectometric interference spectroscopy, more applications of this method will be given in following. 

The possibilities of measuring time-resolved hybridization in this parallel setup are shown in Figure 23, and it even allows to obtain kinetic information for all spots in parallel. Since reflectometric interference... 

Yan H.M., Kraus G., Gauglitz G., Detection of Mixtures of Organic Pollutants in Water by Polymer Film Receptors in Fibre-Optical Sensors Based on the Reflectometric Interference Spectrometry, Anal ChimActa 1995 312 1-8. 

Mehlmann M., Garvin A., Steinwand M., Gauglitz G., Coupling of reflectometric interference spectroscopy with MALDI-MS, in preparation. 

Birkert O., Tunnemann R., Jung G., Gauglitz G., Label-Free Parallel Screening of Combinatorial Triazine Libraries Using Reflectometric Interference Spectroscopy, Anal Chem 2002 74 834. 

Birkert O., Gauglitz G., Development of an assay for label-free high-throughput screening of thrombin inhibitors by use of reflectometric interference spectroscopy, AnalBioanal Chem 2002 372 141-147. 

Sauer M., Brecht A., Charisse K., Stemmier I., Gauglitz G. and Bayer E., Interaction of Chemically Modified Antisense Oligonucleotides with Sense DNA A Label-Free Interaction Study with Reflectometric Interference Spectroscopy, Anal Chem 1999 71 2850. 

Reichl, D. Krage, R. Krumme, C. Gauglitz, G., Sensing of volatile organic compounds using a simplified reflectometric interference spectroscopy setup, Appl. Spectrosc. 2000, 54, 583 586... 

In this section an overview of the numerous methods and principles for the discrimination of enantiomers is given. First, the interaction principles of the polymer-based methods adapted from chromatographic procedures are illustrated. The discrimination of enantiomers was achieved some decades ago by using different types of stationary materials, like cyclodextrins or polymer-bonded amide selectors. These stationary-phase materials have successfully been appointed for label-free optical sensing methods like surface plasmon resonance (SPR) or reflectometric interference spectroscopy (RIfS). Furthermore, various successful applications to optical spectroscopy of the well-established method of fluorescence measurements for the discrimination of enantiomers are described. 

Fig. 5 Relative reflectometric interference spectroscopy sensor signals (normalised with regard to the layer thickness without analyte gas) of two chiral sensors (S-sensor, grey line R-sensor, black) and an additional SE-30 sensor (points) upon exposure to mixtures of different enantiomeric composition (in percent) of N-TFA-Ala-OMe [18]...

A chemical sensor is a device that transforms chemical information into an analytically useful signal. Chemical sensors contain two basic functional units a receptor part and a transducer part. The receptor part is usually a sensitive layer, therefore a well founded knowledge about the mechanism of interaction of the analytes of interest and the selected sensitive layer has to be achieved. Various optical methods have been exploited in chemical sensors to transform the spectral information into useful signals which can be interpreted as chemical information about the analytes [1]. These are either reflectometric or refractometric methods. Optical sensors based on reflectometry are reflectometric interference spectroscopy (RIfS) [2] and ellipsometry [3,4], Evanescent field techniques, which are sensitive to changes in the refractive index, open a wide variety of optical detection principles [5] such as surface plasmon resonance spectroscopy (SPR) [6—8], Mach-Zehnder interferometer [9], Young interferometer [10], grating coupler [11] or resonant mirror [12] devices. All these optical... 

The interaction behaviour of the homologous alcohols methanol, ethanol and 1-propanol and the ultramicroporous polymer Makrolon was investigated by three different optical methods spectral ellipsometry, surface plasmon resonance and reflectometric interference spectroscopy. 

Fig. 5.15. Illustration of the basic principle of the reflectometric interference spectroscopy (RifS) biosensor. See text for details of the working principle.

Mehlmann, M., Garvin, A. M., Steinwand, M., Gauglitz, G. (2005). Reflectometric interference spectroscopy combined with MALDI-TOF mass spectrometry to determine quantitative and qualitative binding of mixtures of vancomycin derivatives. Anal. 

Reflectometric Interference Spectroscopy (RIfS) in the Liquid Phase... 

Cyclohexapeptide monolayers on quartz microbalances are able to discriminate between different analytes in the liquid phase (see Section 10.5.1). On the basis of these results, we also have immobilized cyclopeptides (Fig. 10.14) on glass transducers. In this case, the interaction between cyclopeptides and analytes was monitored by reflectometric interference spectroscopy (RIfS) [98], RIfS is an optical detection method in which the phenomenon of reflection and interference of light at phase boundaries is used to measure changes in optical thickness (refractive index x layer thickness) of transparent films... 

Isoproturon Label-free immunosensor using reflectometric interference spectroscopy 0.7pgl-> water [148]... 

An increase in optical thickness of the thin film, caused by e.g. ligand adsorption, will shift the interference spectrum to a higher wavelength and widen the distance between the minima and maxima in the inteference spectra as illustrated in Fig. 14.45b. This is the principle behind reflectometric interference spectroscopy, or Rifs [315]. Due to the high sensitivivity of the detection (ppm levels of phase shifts can be measured [316]), the RIfS device has been successfully used for the study of various biological interactions at surfaces, such as mouse anti-atrazine/ atrazine [317] and DNA-ligand interactions [318]. The principle of RIfS also allows the construction of low-cost devices. 

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