High resolution mass spectrometry HRMS

When using high resolution mass spectrometry (HRMS), the characteristic m/z for 2,3,7,8-TCDD are 319.8965 and 321.8936. The m/zforthe corresponding 37C14- and 13C12-isomers in HRMS are 327.8847 and 331.9367, respectively. 

Mass spectrometry remains of limited use for the characterization of dioxetanes however, numerous relatively stable 1,2-dioxetanes have been prepared over the last decade allowing not only for the detection of their parent ions but also allowing for high-resolution mass spectrometry (HRMS) measurements to be taken. See references associated with structures depicted in Figure 1 or Table 1. 

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. 

Mass spectrometry (MS) provides the molecular weight and valuable information about the molecular formula, using a very small sample. High-resolution mass spectrometry (HRMS) can provide an accurate molecular formula, even for an impure sample. The mass spectrum also provides structural information that can confirm a structure derived from NMR and IR spectroscopy. 

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-... 

The molecular formula of a molecule can also be defined by high resolution mass spectrometry (hrms). The observed mass for the molecular ion or pseudo molecular ion must normally be within 5ppm of the calculated mass for El (electron impact) measurements, or within lOppm for Cl (chemical ionization) measurements. It is important to note that high resolution mass spectrometry confirms that some molecules of a particular molecular formula are present in the sample, but does not give any indication of purity. Some other evidence of compound purity will therefore be required. 

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... 

According to Vikelsoe et al. cleanup is not necessary when high resolution mass spectrometry (HRMS) is used as detector due to the high selectivity of the technique. Therefore, soil samples were spiked with the deuterated surrogates and extracted by shaking in DCM for 2 h. The extract was concentrated under nitrogen, redissolved in hexane and analyzed by GC or HRMS. Blank responses were subtracted from sample responses. 

More recently, substituted transient thioxosilanes have been obtained by a retro-ene reaction according to Scheme 6.3. In this study, the thermolysis of several thiosilanes such as 9a and 9b (Scheme 6.3) was examined using both high-resolution mass spectrometry (HRMS) and photoelectron spectroscopy (PES). While monomeric (/-Pr)2Si=S (10b) was obtained from 9b and identified independently by both methods employed, 10a was not observed in the mass spectrum of the thermolysis products of 9a. Moreover, the detection of monomeric 10a by its PE spectrum was hampered by strong bands due to allene and undecomposed precursor obscuring bands assumed to stem from lOa.PH... 

The solvolysis product is already a complex mixture ant it is important to identify the major components which are present into it. This was done by High Resolution Mass Spectrometry (HRMS). 

The methanol fractions ( 4) of two of the light-duty diesel particulate extracts were also analyzed by HRGC/MS and high resolution mass spectrometry (HRMS) in an attempt to tentatively... 

Mass spectrometry/mass spectrometry (MS/MS)(10) and high resolution mass spectrometry (HRMS) (3,7,10) have been used to show that a large number of nitro-PAH are potentially present in these extracts. However, only a few specific isomers have been positively identified. The purpose of this paper is to describe techniques for identifying a large number of nitro-PAH which may be present in these samples. 

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