Spectrometer Designs and Applications

Hill, J.A. Biller, J.E. Martin, S.A. Biemann, K. Yoshidome, K. Sato, K. Design Considerations, Calibration and Applications of an Array Detector for a Four-Sector Tandem Mass Spectrometer. Int. J. Mass Spectrom. Ion Proc. 1989, 92,211-230. 

Since the development of HPLC as a separation technique, considerable effort has been spent on the design and improvement of suitable detectors. The detector is perhaps the second-most important component of an HPLC system, after the column that performs the actual separation it would be pointless to perform any separation without some means of identifying the separated components. To this end, a number of analytical techniques have been employed to examine either samples taken from a fraction collector or the column effluent itself. Although many different physical principles have been examined for their potential as chromatography detectors, only four main types of detectors have obtained almost universal application, namely, ultraviolet (UV) absorbance, refractive index (RI), fluorescence, and conductivity detectors. Today, these detectors are used in about 80% of all separations. Newer varieties of detector such as the laser-induced fluorescence (LIE), electrochemical (EC), evaporative light scattering (ELS), and mass spectrometer (MS) detectors have been developed to meet the demands set by either specialized analyses or by miniaturization. 

Selected topics in Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry instrumentation are discussed in depth, and numerous analytical application examples are given. In particular, optimization ofthe single-cell FTMS design and some of its analytical applications, like pulsed-valve Cl and CID, static SIMS, and ion clustering reactions are described. Magnet requirements and the software used in advanced FTICR mass spectrometers are considered. Implementation and advantages of an external differentially-pumped ion source for LD, GC/MS, liquid SIMS, FAB and LC/MS are discussed in detail, and an attempt is made to anticipate future developments in FTMS instrumentation. 

A 7] The fiber-coupled spectrometer is actually designed for applications with hand-held devices. A combination of micro injection molding and an electroforming process allows the production of a high-performance but low-cost device. The optical grating is, for example, replicated in plastic to reduce costs. 

A few scanning dispersive VCD instruments are still in use for biological applications in the mid-IR region [46,47]. In 2009, a newly designed and optimized dispersive VCD instrument was reported [47]. A collection of spectra for peptides and proteins having different dominant secondary structures (alpha-helix, beta-sheet, and random coil) measured with this new instrument showed substantially improved signal-to-noise (S/N) ratios as compared with the earlier version. The instrument provides protein VCD spectra for the amide I region that are of comparable or better quality than those obtained with a standard commercial FTIR-VCD spectrometer [47]. 

Aerosol centrifuges are useful in the laboratory but have little application in air cleaning. When care is taken so that the aerosol enters the rotating annulus at a single point, the units are often called aerosol spectrometers. A discussion of the calibration and operation of the popular Stober spectrometer design (Stober and Flachsbart, 1969) is given by Martonen (1989). 

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