Electrospray negative-ion

It has been shown [18] that when high cone-voltages were used in conjunction with negative-ion electrospray, phosphopeptides produce diagnostic ions at m/z 63 (P02 ) and m/z 79 (P03 ). LC-MS analysis of a trypsin digest of bovine... 

The study of sulfated standards enabled certain structural features to be associated with particular ions that appeared in their negative-ion electrospray MS-MS spectra. The following is reproduced from this paper [23] ... 

LC/MS/MS. LC/MS/MS is used for separation and quantitation of the metabolites. Using multiple reaction monitoring (MRM) in the negative ion electrospray ionization (ESI) mode, LC/MS/MS gives superior specificity and sensitivity to conventional liquid chromatography/mass spectrometry (LC/MS) techniques. The improved specificity eliminates interferences typically found in LC/MS or liquid chro-matography/ultraviolet (LC/UV) analyses. Data acquisition is accomplished with a data system that provides complete instmment control of the mass spectrometer. 

Wu, Z. Jernstroem, S. Hughey, C. A. Rodgers, R. R Marshall, A. G. Resolution of 10,000 compositionally distinct components in polar coal extracts by negative-ion electrospray ionization Fourier transform ion cyclotron resonance. Mass Spectrom. Ener. Fuels 2003,17, 946-953. 

Jemal M., Xia Y., and Whigan D.B., 1998. The use of high-flow high performance liquid chromatography coupled with positive and negative ion electrospray tandem mass spectrometry for quantitative bioanalysis via direct injection of the plasma/serum samples. Rapid Commun Mass Spectrom 12 1389. 

Fig. 19.3. Example of high-resolution experiments on complex mixtures, showing the multiple elemental compositions possible at a single nominal mass. Top panel four elemental compositions at m/z 225 in the positive ion electrospray mass spectrum of a diesel oil feedstock (from Wu et al. [17]). Bottom panel multiple compositions at m/z 455 in the negative ion electrospray spectrum of olive oil (from Marshall et al. [18]).

A proposed mechanism of this reaction was reported by Magnus and Principle [10], which is nowadays widely accepted (Scheme 1). Recently, negative-ion electrospray collision experiments have confirmed this mechanism in detail [11]. Starting with the formation of the alkyne-Co2(CO)6 complex 2, olefin 3 coordination and subsequent insertion takes place at the less hindered end of the alkyne. The in situ formed metallacycle 4 reacts rapidly under insertion of a CO ligand 5 and reductive elimination of 6 proceeds to liberate the desired cyclopentenone 7. It is important to note that all the bond-forming steps occur on only one cobalt atom. The other cobalt atom of the complex is presumed to act as an anchor which has additional electronic influences on the bond-forming metal atom via the existing metal-metal bond [12]. 

Spell JC, Srinivasan K, Stewart JT, Bartlett MG. 1998. Supercritical fluid extraction and negative ion electrospray liquid chromatography tandem mass spectrometry analysis of phenobarbital, butalbital, pentobarbatal and thiopentoal in human serum. Rapid Commun Mass Spectrom 12 890. 

Cataldi TRI, Rubino A, Lelario F, Bufo SA (2007) Naturally occurring glucosinolates in plant extracts of rocket salad (Eruca Sativa L.) identified by liquid chromatography coupled with negative ion electrospray ionization and quadrupole ion-trap mass spectrometry. Rapid Commun Mass Spectrom 21 2374-2388... 

The negative ion electrospray MS of fatty acid hydroperoxides exhibits various typical features that may be useful for characterization of this type of compounds, such as loss of small neutral molecules and fragmentation associated with the position of the OOH group. The [M — H] and [M — H2O peaks are usually most abundant and cleavage of the double bond allylic to the hydroperoxy group is also observed. The features of the fragmentation after loss of H2O in the MS of a fatty acid hydroperoxide are the same as those observed in the MS of the analogous keto acid . ... 

Figure A.3A.3 LC/MS analysis of a dietary supplement consisting of extract of Trifolium pratense (red clover). Reversed-phase C18 HPLC and negative ion electrospray ionization mass spectrometry were used with a quadrupole mass spectrometer analyzer (Agilent also see Table A.3A.1). The map illustrates the abundance of information provided by this hyphenated technique with HPLC mass chromatograms in one dimension and mass spectra in another dimension.

AJP Hofte, RAM van der Hoeven. Characterization of hop acids by liquid chromatography with negative ion electrospray ionization mass spectrometry. J Am Soc Brew Chem 56 118-122, 1998. 

A critical review of the inherent limitations of modern PFA analytical methods is available in Martin et al. [18], but some examples are discussed here. For quantitative determination, the HPLC system is often interfaced to a Micromass or Sciex tandem mass spectrometer operated in the negative ion electrospray mode. Instrumental parameters are optimized to transmit the [M - H] ion for all analytes (Table 5). When possible, multiple daughter ions are monitored, but quantitation is generally based on a single product ion (Table 5, Fig. 4). In the electrospray tandem mass spectrometry (ES MS/MS) system, the 499 Da -> 80 Da transition can provide a stronger signal than... 

E. Vukelic, A. D. Zamfir, L. Bindila, M. Froesch, J. Peter-Katalinic, S. Usuki, and R. K. Yu, Screening and sequencing of complex sialylated and sulfated glycosphingolipid mixtures by negative ion electrospray Fourier transform ion cyclotron resonance mass spectrometry, J. Am. Soc. Mass Spectrom., 16 (2005) 571—580. 

R.W. Read and R.M. Black, Analysis of the sulfur mustard metabolite l,l/-sulfonylbis[2-5-(A-acetylcysteinyl)ethane] in urine by negative ion electrospray liquid chromatography-tandem mass spectrometry, J. Anal. Toxicol, 28, 352-356 (2004). 

Harvey, D.J. (2005) Fragmentation of negative ions from carbohydrates Part 1. Use of nitrate and other anionic adducts for the production of negative ion electrospray spectra from N-linked carbohydrates. J. Am. Soc. Mass Spectrom., 16 (5), 622-30. 

Carbon dioxide protected pyrroles and indole (carbamates), generated by treatment of the iV-lithiated heterocycles with gaseous CO2, can be easily tracked by negative ion electrospray ionization mass spectrometry (ESI-MS) revealing invariable loss of CO2 from the anion <2002JMP541>. 

The cyanocuprates of thiophene have been discussed earlier <1996CHEC-II(2)491>. An attempt has been made to use negative ion electrospray ionization mass spectrometry for obtaining information on the solution composition of organocuprates such as 225 and 226 in THF <19990M1571>. 

Ghassempour, A. et al. Monitoring of N-nitrosodiethanolamine in cosmetic products by ion-pair complex liquid chromatography and identification with negative ion electrospray ionization mass spectrometry. J. Chromatogr. A. 2008, 1185,43-48. 

The presence of pentosyUiexosides, trisaccharides and tetrasaccharides has been reported in different wines using positive- and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (Cooper and Marshall 2001). Nevertheless, at present there are still a number of minor carbohydrates in wines without a conclusive identification. 

Figure 13.3. Two-dimensional map showing the LC-MS analysis of an extract of red clover under investigation for the management of menopause. Reversed phase separation was carried out using a Ci8 HPLC column in the time dimension and negative ion electrospray mass spectrometry was used for compound detection and molecular weight determination in the second dimension.

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