High resolution mass spectrometry system

Keywords Data mining Deconvolution software Degradation products Emerging contaminants High resolution mass spectrometry system Hybrid mass spectrometry system Metabolites Non-target analysis Screening analysis Transformation products Surface water UHPLC Unknown compounds... 

A systematic investigation of the free amino acids of the Leguminosae led to the isolation of a novel ninhydrin-positive compound from the leaves of Derris elliptica Benth. (Papilionidae) (93). This substance was analyzed as C6H,3N04 (microanalysis and high resolution mass spectrometry) and was shown to be an amino alcohol. The absence of a carbonyl in the 1R, the loss of 31 mass units in the mass spectrum, and a positive periodate cleavage reaction were best embodied into a dihydroxydihydroxymethylpyrrolidine structure. The relative simplicity of the NMR spectra (three peaks in the 13C spectrum four spin-system in the H spectrum) pointed out a symmetrical structure. Inasmuch as the material was optically active ([a]D 56.4, c = 7, H20), meso structures were ruled out, and the 2R, 3R, 4R, 5R relative configuration was retained (93). This structure (53) was further confirmed by an X-ray determination (94). 

Quite often a normal electron ionization mass spectrum appears insufficient for reliable analyte identification. In this case additional mass spectral possibilities may be engaged. For example, the absence of the molecular ion peak in the electron ionization spectrum may require recording another type of mass spectrum of this analyte by means of soft ionization (chemical ionization, field ionization). The problem of impurities interfering with the spectra recorded via a direct inlet system may be resolved using GC/MS techniques. The value of high resolution mass spectrometry is obvious as the information on the elemental composition of the molecular and fragment ions is of primary importance. 

A frequent complication in the use of an insoluble polymeric support lies in the on-bead characterization of intermediates. Although techniques such as MAS NMR, gel-phase NMR, and single bead IR have had a tremendous effect on the rapid characterization of solid-phase intermediates [27-30], the inherent heterogeneity of solid-phase systems precludes the use of many traditional analytical methods. Liquid-phase synthesis does not suffer from this drawback and permits product characterization on soluble polymer supports by routine analytical methods including UV/visible, IR, and NMR spectroscopies as well as high resolution mass spectrometry. Even traditional synthetic methods such as TLC may be used to monitor reactions without requiring preliminary cleavage from the polymer support [10, 18, 19]. Moreover, aliquots taken for characterization may be returned to the reaction flask upon recovery from these nondestructive... 

Satisfactory CH microanalyses for several / -sultones <1999TL7417> and several pentacoordinate l, 2A4- and 1,2A6-oxathietanes <1996JA697, 1996JA12455> have been reported over the last decade. While there is no CH micro-analytical data for simple 1,2-oxathietanes, / -sultines, 2-oxathietes, 1,3-oxathietanes, and their S-oxides, occasionally high-resolution mass spectrometry (HRMS) data are reported. Presumably, this reflects the thermal instability of these systems. 

The increasing accessibility of bench-top LC-MS systems to researchers of all disciplines, combined with the tandem and high-resolution mass spectrometry capabilities of such instruments, will only increase the number of applications to which LC-MS can be directed. The examples documented in this chapter illustrate some of the diversity and power of the techniques, including analytical applications for known analytes in various matrices, metabolomic analysis, the tentative structural identification of novel compounds, and the screening of extracts for minor, and perhaps novel, components of the alkaloidal profile of plants. 

PCDE analyses can be performed by high resolution gas chromatography (HRGC) combined with low resolution mass spectrometry (LRMS) or using HRGC combined with high resolution mass spectrometry (HRMS). For example, a Hewlett Packard 5970 mass selective detector system, which is a qua-drupole mass analyzer, has been used as an LRMS instrument in Finnish studies [33, 57, 113, 114, 122-125, 139]. Compared to LRMS, HRMS is more sensitive, allows less sample cleanup, and eliminates interference more effec-... 

Institute, as well as Correlogics Systems, for their collaboration on using high-resolution mass spectrometry to diagnose ovarian cancer. 

Dehydrocancentrine-B, a cherry-red alkaloid isolated from the same source, had the same functional groups as cancentrine (NMR, IR). However, its IR spectrum indicated the presence of an additional double bond in agreement with the molecular formula (C36H32N2O7) obtained by high-resolution mass spectrometry (HRMS). The mass spectrum was very similar to that of cancentrine with the exception that ions from the cularine half of the molecule appeared two mass units lower. Thus there were ions at m/e 361 (C21H15NO5) and m/e 348 (C20H14NO5) arising from fissions a + b and a -l- c, respectively (Scheme 1). This indicated that the extra double bond was in the cularine part of the molecule and must be located at the only available position, namely, C-31—C-32 (12). The NMR spectrum supported the location of the double bond in this position by the presence of a fourth AB system one half of which was visible at S 6.25 (Jab = 7.0 Hz). The location of the substituents and the relative stereochemistry of the alkaloid were shown to be identical with those... 

Laser ablation mass spectrometry (LAMS) uses a pulsed laser to destroy zeolite structures, release and ionize molecules occluded within the zeolite pores. High resolution mass spectrometry can then be used to study the ions produced. This paper describes LAMS studies on two well defined model systems hexamethylbenzene(HMB) adsorbed in NaFAU, and the tetrapropylammonium(TPA) template in MFI. It is shown that LAMS can be used to identify the adsorbed species. 

High resolution gas chromatography-high resolution mass spectrometry (HRGC/HRMS) also allows improving LODs. An example is PBDE determination in air, dust, and clothes dryer lint samples using this technique (Toms et al. 2009 Schecter et al. 2009). When C-labeled internal standards are added, analysis can be carried out by the isotope dilution technique. For example, PBDEs were analyzed in house indoor dust of different countries by GC/isotope dilution-HRMS (Sjodin et al. 2008). When volatiles are analyzed, another possibility is to use multidimensional GC/MS-olfactometry in a system equipped with a non-polar precolumn and polar column in series. This system was used to determine VOCs from swine barn particulate matter (Cai et al. 2006). 

The earliest work in high-resolution mass spectrometry produced spectra similar in appearance to that in Figure 3.3a. Chart records were obtained by slowly varying the magnetic field of a Nier-Johnson mass spectrometer. The time (or distance along the chart) between the centers of unknown and reference peaks and the known reference masses was used to determine the exact masses of the unknown ions. Current instruments, with their computerized data acquisition systems, automatically identify the reference masses, generate the internal calibration table, and calculate the accurate masses. 

One drawback to using high-resolution mass spectrometry is long analysis times. MSI of individual rat brain sections is typically performed within a couple of hours on a unit resolution system, whereas the same analysis on... 

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