Detection principles, molecular

Specificity. The potentially very high analytical specificity of tandem mass spectrometry as HPLC detector results from using the molecular mass of the analyte and its specific disintegration behaviour as detection principle. 

EPR spectroscopy is a powerful tool to determine magnetic, electronic and structural properties of molecular systems with unpaired electrons. Due to its detection principle, EPR detects paramagnetic species with non-zero electron... 

D. Bassi, Detection principles, in Atomic and Molecular Beam Methods, ed. by G. Scoles (Oxford Univ. Press, London, 1992), pp. 153 ff. 

In all cases where molecules cannot be distinguished based on their molecular mass within the experimental error (isobaric compounds), additional and complementary detection principles are imperative. The related detector modules can be added either serially or in parallel by splitting the LC column effluent, depending on the detection principle. 

D. Bassi Detection principles. In Atomic and Molecular Beam Methods, ed. by... 

In 1989, the Fuji group developed the method for detection of chemical species in the gas phase with use of Li ion attachment to chemical species [11-13]. The principle is based upon a phenomenon that LL ions get attached to chemical species (M) by means of intermolecular association reactions to produce (M + Li)+ adduct ions. Then they are transferred to a mass spectrometer for mass analysis. This approach is exactly the same to cationization for detection of molecular species. Since the potential of Li ion attachment in MS has not yet been reahzed, they attempted to reveal and explore some of the unique properties of Li I AMS. Li ions have been chosen as reactant ions, because the affinity of the species is the highest among all the alkali metal ions. This technique provides mass spectra of quasi-molecular ions formed by lithium ion attachment to the chemical species (M) under high pressure. Results are obtained in the form of trace of LL adduct ions (M + Li)+ (also referred as cationized molecules). The newly developed lAMS [10], manufactured by instmmental maker (Canon Anelva Corp., Japan), exhibits several advantages over conventional mass spectrometers. Currently, ion association MS is available commercially in a various form. Recently, some reviews have been published on the principles, instmmental techniques, unique characteristics, and applications of I AMS [15-20]. 

A number of physical devices with chemical sensitivity have been developed previously, including the quartz crystal microbalance (QCM) and other acoustic wave devices, semiconductor gas sensors, and various chemically sensitive field effect transistors. However, based on their intrinsic detection principles, most of the known solid state chemical sensors are not selective, i.e., they respond to more than one or a few chemical species. There is an urgent demand for new families of selective, microscope sensors that can eventually be integrated into microelectronic circuits. We have embarked on a program aimed at the design of conceptually new microporous thin films with molecular recognition capabilities. On the surface of chemical sensors, these membranes will serve as "molecular sieves that control access of selected target molecules to the sensor surface. 

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