Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Electrospray mass spectrum appearance

The positive mode electrospray mass spectrum of X exhibits a peak at m/z 126. Compound X reacts with chloroauric acid, HAuCLt, to give a salt, Y, which contains two square planar Au(III) environments. The anion in Y has Z>4h synunetry. The H NMR spectrum of a DMSO-de solution of Y exhibits the following signals 6/ppm 9.07 (s, IH), 7.92 (br, 2H), 7.74 (overlapping signals, 2H), 4.38 (t, 2H), 3.86 (s, 3H), 3.34 (m, 2H). The electrospray mass spectrum of Y shows peak envelopes at m/z 428 and 126 (positive mode), and 339 (negative mode). The peak envelope at m/z 339 consists of four peaks, and that at m/z 428 exhibits three dominant peaks at m/z 428, 429 and 432. Identify X and Y, and interpret the data. Rationalize the appearance of the mass spectra. [Pg.297]

The flow rate of liquid in the HPLC-electrospray system is paramount in determining performance both from chromatographic and mass spectrometric perspectives. The flow rate affects both the size and size distribution of the droplets formed during the electrospray process (not all droplets are the same size) and, consequently, the number of charges on each droplet. This, as we will see later, has an effect on the appearance of the mass spectrum which is generated. It should also be noted that the smaller the diameter of the spraying capillary, then... [Pg.159]

Although this technique was introduced in early 1990s, it was the introduction of a MALDI-TOF instrument capable of 50 ppm mass accuracy that made PMF a routine procedure. In MALDI-TOF mass spectrometry, peptides appear as singly charged species in the mass spectrum (Figure 4.4-1). Unlike an electrospray (ESI) mass spectrum, which displays multiply charged species, the MALDI-TOF spectrum is simple to interpret. PMF can also be used to identify proteins in ESI spectra, but it is seldom used because the peptide masses would need to be decon-voluted for each search. [Pg.423]

Electrospray mass spectrometry is a recently developed technique for looking at large molecules with a mass spectrometer. In this technique, molecular ions, each associated with one or more H" " ions, are prepared under mild conditions in the mass spectrometer. As an example, a protein (P) with a molecular mass of 11,812 gives clusters of the type (P + 8H), (P -I- 7H) ", and (P + 6H). At what mass-to-charge values do these three clusters appear in the mass spectrum ... [Pg.610]

In contrast to FAB-MS and MALDI-MS, electrospray mass spectra are characterized by multiply charged ions. The raw data obtained following ES-MS analyses is complex because ions can carry a range of charges due to the different ionisable sites in the molecule. Multiple m/z signals are therefore recorded for each mass value. Fortunately these data can be processed using a simple computer algorithm to produce a mass spectrum of comparable appearance to a FAB or MALDl spectrum. [Pg.920]

Electrospray is an unusual mass spectrometry technique in that it allows the study of the three-dimensional structure of compounds, particularly proteins, in solution as it is believed that this is relatively unchanged when ions are transferred to the vapour phase. This type of application will be discussed in more detail in Chapter 5 but attention is drawn at this point to the previous comments regarding the effect that the HPLC conditions, such as pH, may have on the appearance of an electrospray spectrum and the conformational deductions that may be made from them. [Pg.179]

Only one major compound (SF-X) was present in the estrogenically active fractions, and this was isolated using semipreparative HPLC. The principles of separation are the same as for qualitative HPLC (see Section 25.4.1.2), with the difference that higher amounts of material can be loaded onto the ODS-column (Alltech, Econosil, Cig lOp, 250x22mm). For the identification of SF-x, a combination of spectroscopic techniques was used. Electrospray ionization in the mass spectrometer (HPllOO LC/MSD, Hewlett-Packard) with positive ionization mode gave a pseudo-molecular ion with m/z=439. H-NMR, C-NMR, DEPT, HMQC, and COSY spectra were recorded on a Varian-300 (300MHz) spectrometer. Analysis of the COSY spectram showed the presence of a lavandulyl (5-methyl-2-isopropenyl-hex-4-enyl) side chain. From the HMQC spectrum and a DEPT experiment, it appeared that SF-x possesses a disubstituted flavanone skeleton. [Pg.529]


See other pages where Electrospray mass spectrum appearance is mentioned: [Pg.725]    [Pg.560]    [Pg.65]    [Pg.494]    [Pg.195]    [Pg.700]    [Pg.165]    [Pg.250]    [Pg.23]    [Pg.264]    [Pg.268]    [Pg.269]    [Pg.271]    [Pg.104]    [Pg.99]    [Pg.263]    [Pg.194]    [Pg.163]    [Pg.134]    [Pg.275]    [Pg.9]    [Pg.21]    [Pg.399]    [Pg.303]    [Pg.114]    [Pg.63]    [Pg.285]    [Pg.287]    [Pg.128]    [Pg.508]    [Pg.175]    [Pg.245]    [Pg.256]    [Pg.117]    [Pg.63]    [Pg.185]    [Pg.135]    [Pg.843]    [Pg.266]    [Pg.303]   
See also in sourсe #XX -- [ Pg.106 , Pg.107 , Pg.108 , Pg.109 , Pg.110 , Pg.111 , Pg.112 , Pg.113 , Pg.114 , Pg.115 , Pg.116 ]

See also in sourсe #XX -- [ Pg.106 , Pg.107 , Pg.108 , Pg.109 , Pg.110 , Pg.111 , Pg.112 , Pg.113 , Pg.114 , Pg.115 , Pg.116 ]




SEARCH



Appearance

Electrospray mass spectrum

© 2024 chempedia.info