Advanced Scanning Modes

Since modern FTIR spectrometers can operate in a rapid scan mode with approximately 50 ms time resolution, TRIR experiments in the millisecond time regime are readily available. Recent advances in ultra-rapid scanning FTIR spectroscopy have improved the obtainable time resolution to 5 ms. Alternatively, experiments can be performed at time resolutions on the order of 1-10 ms with the planar array IR technique, which utilizes a spectrograph for wavelength dispersion and an IR focal plane detector for simultaneous detection of multiple wavelengths. ... 

Advanced mass spectrometry enables the detection of higher-molecular-weight compounds that can be expected to retain more specific structure information contained in the original complex materials. The application of MS/MS using various scan modes will further extend the capabilities for identification of compounds in complex mixtures. Precursor scan techniques improve insight into the origin of ions in complex pyrolysates... 

In Figure 4.22, the FTIR spectra of dehydrated samples of the acid zeolites, H-SSZ-24 and H-ZSM-11, in the range from 3000 to 4000 cm-1 are shown [65], The measurement of the FTIR spectra was carried out in a Bio-Rad FTS 40A FTIR spectrometer with aresolution of 8cm-1 controlled by the Bio-Rad WIN IR software in an Advanced Scan Menu-Kinetics mode [65,66], To obtain the spectra, 30 scans were made. 

A suitable description of a peak for advanced Scherrer analysis uses the expression in terms of the centroid and the variance of a peak. For the possible computation of these values, the explicit definitions are given in Equation (9) for the centroid and in Equation (10) for the variance expressed in units of the 20 scale. Conventions for a peak profile measured in a step-scan mode are as follows 20 = position of a peak increment, 1(20) = the background corrected intensity in cps for the increment, A20 = width of the increment ... 

Recent advances in protein analysis by MS are due to the introduction of electrospray ionization (ESI), matrix-assisted laser desorption ionization (MALDI), MSN scan modes, as well as improvements in instrument sensitivity, resolution, and mass accuracy. With these improved techniques, researchers will continue to use MS to help elucidate primary, secondary, and to a lesser extent, tertiary structure of proteins. 

Advanced TCSPC devices usually have spectrum-scan modes that reeord several spectra in different time windows simultaneously. The prineiple is shown in Fig. 5.20. The wavelength is scanned, and for each wavelength a fluorescence decay curve is recorded. The counts in the time channels of the deeay eurve are averaged within selectable time intervals. The averaged counts are stored as functions of the wavelength. Several independent time windows can be used simultaneously. Therefore the efficiency is better than for a system that uses a single window discriminator. 

The two chapters that were selected for this topic one on GC-ion trap mass spectrometry, by SabUer and Fujii and the other by Schroder on LC-MS in environmental analysis give an excellent contribution to the application of GC-MS and LC-MS to environmental analysis. Both chapters include many practical aspects and examples in the environmental field and also cover the historical perspective of the techniques and show the perspective on ionisation and scanning modes. Advances achieved in GC-ion trap by the use of external ion sources and GC/MS/MS possi-bihties are discussed. The LC-MS chapter provides an overview of the first applications of LC/MS interfacing systems, such as moving belt, direct Uquid introduction (DLI) and particle beam (PB), and then on the more recent soft ionisation techniques, like thermospray and atmospheric pressure ionisation interfacing systems. 

What is generally meant by wide-field microscopy is any microscope whereby image formation takes place by the optics without scanning the lens directly forms an image, which can be projected on a camera or observed through the eye piece. Before the development of confocal microscopy and other scanning microscopy modes, this was the only way to perform microscopy. In the biomedical sciences, wide-field fluorescence microscopy is still widely used and offers a number of advantages over confocal and other advanced microscopy modes. 

Lack of advances in optics has hampered improvements in microscopic imaging. Development of adaptable, inexpensive fiber optics to transmit high-energy femtosecond pulses from mode-locked lasers, custom phase plates, and miniature laser beam scanners for endoscopic microscopy instruments offer the potential for enormous advances in laser scanning microscopy for various applications, including medical diagnostics and surgery. 

---