Combined mass spectrometry methods

Mass spectrometry combines exquisite sensitivity with a precision that often depends more on the uncertainties of sampling and sample preparation than on those of the method itself. Mass spectrometry is a supreme identification and recognition method in polymer/additive analysis through highly accurate masses and fragmentation patterns quantitation is its weakness. Direct mass spectrometry of complex polymeric matrices is feasible, yet not often pursued. Solid probe ToF-MS (DI-HRMS) is a breakthrough. Where used routinely, mass spectrometrists are usually still in charge. At the same time, however, costs need to be watched. 

Fascinating possibilities are opened by combining ACE with different mass spectrometry (MS) methods in order to overcome the main disadvantage of classical CE and IJV detection the lack of sensitivity. The hyphenated methods are very sensitive and allow us to characterize interactions of very small quantities of molecular entities. 

The combination of ACE with mass spectrometry (hyphenation methods) will increase significantly its applicability in pharmaceutics and biopharmaceutics. 

The pyrolysis methods applied in this study are used as a tool for a general characterization of the organic matter from the sediments. We describe here the results from screening of estuarine and open sea sediment samples by automated pyrolysis low voltage mass spectrometry combined with factor-discriminant analysis. Characteristic mass peaks resulting from this procedure were investigated in more detail by pyrolysis-tandem mass spectrometry and pyrolysis-photoionization GCMS. 

Secondary-ion mass spectrometry (SIMS) can be used to detect the presence and the depth distribution of a specific impurity by etching out ions (secondary ions) from a material with a Cs+ or C>2+ ions probe, and measuring the impurity peak by mass spectrometry. This method provides a chemical signature of the impurity, with possible interferences, however, between atomic and molecular ions with the same masses and charges. It cannot discriminate between the isolated impurity and complexes or precipitates in which it is involved. Its sensitivity depends on the background of impurity. SIMS has been used for the detection of boron acceptor in CVD diamond [39]. These absolute methods of concentration measurements have been combined with spectroscopic measurements, which are easier to perform, to produce spectroscopic calibration factors. 

Isotope-coded affinity tag (ICAT) peptide labeling is an approach that combines accurate quantification and concurrent sequence identification of individual proteins in complex mixtures (Gygi, et al 1999). This method is based on a newly synthesized class of chemical reagents used in combination with tandem mass spectrometry. The method consists of four steps ... 

In this chapter, quantitative applications of mass spectrometry were discussed. In this respect, mass spectrometry is distinctly superior over most other analytical techniques. Mass spectrometry-based methods are more specific and highly sensitive. In combination with high-resolution separation devices, the task of quantitation of real-world samples becomes much easier. A mass spectrometry signal is acquired in the SIM or SRM mode. In SIM, the ion current due to one or more compound-related ions is recorded, whereas in SRM, precursor-product... 

Chen, G., Cao, R, and Liu, R. 2011. A multi-residue method for fast determination of pesticides in tea by ultra performance liquid chromatography-electrospray tandem mass spectrometry combined with modified QuEChERS sample preparation procedure. Food Chem. 125 1406-1411. 

Routine analytical methods typically include micro (graphite furnace) atomic absorption spectrometry and electrochemical approaches such as anodic-stripping voltammetry. More complex, expensive and nonroutine/ research approaches are inductively coupled plasma-mass spectrometry and definitive methods such as thermal ionization-mass spectrometry. These methods have the requisite sensitivity, specificity, and record of reliability for quantification across the range of environmental exposures that humans presently encounter. Combining current instrumental methods with carefiil quality assurance and quality control protocols permits adequate proficiency for even low Pb concentrations, values of 1—2 pg/dl. 

Current efforts are directed towards atomic-scale surface analysis by scanning probe ion mass spectrometry, combining SPM and mass analysis via field desorption and flight time determination [109]. In organic mass spectrometric methods have been reviewed [110],... 

Sepehr, E., Robertson, P., Gilani, G.S., Cooke, G., and Lau, B.P.-Y., An accurate and reproducible method for the quantitative analysis of isoflavones and their metabohtes in rat plasma using hquid chromatography/mass spectrometry combined with photodiode array detection, J. AOAC Int., 89, 1158-1167, 2006. 

Jalali-Heravi M, Zekavat B, Sereshti H. Use of gas chromatography-mass spectrometry combined with resolution methods to characterize the essential oil components of Iranian cumin and caraway. J Chromatogr A 2007 1143 215-26. 

Differentiation between labeled and unlabeled flavor compounds is based on the difference in nuclear masses of the isotopes and on employment of the mass spectrometry method. One of the main advantages of isotope dilution analysis is the high selectivity of the gas chromatography/mass spectrometry combination. The selectivity and the sensitivity of the determination can be further enhanced by the use of different ionization techniques. In most cases, differentiation between the internal standard and the analyte is achieved with the aid of chemical ionization with reactant gases, with the intensities of the molecular ions typically being measured by selective ion monitoring (SIM mode). 

Although GGMS is the most widely used ana lytical method that combines a chromatographic sep aration with the identification power of mass spectrometry it is not the only one Chemists have coupled mass spectrometers to most of the mstru ments that are used to separate mixtures Perhaps the ultimate is mass spectrometry/mass spectrome try (MS/MS) m which one mass spectrometer gener ates and separates the molecular ions of the components of a mixture and a second mass spec trometer examines their fragmentation patterns ... 

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