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English
J. Mass Spectrom. Soc. Jpn., 49(6), 219-223, 2001
Chlorinated aromatic compounds are well-known environmental pollutants and their toxicity often depends dramatically on the chlorine substitution pattern within a homological group. Analysis of extremely toxic environmental pollutants such as dioxins requires high sensitivity, typically in the parts-per-trillion (ppt) range. Mass spectrometry (MS), being the most sensitive of analytical methods, has been used for pollutant analysis, but conventional mass spectrometry alone cannot be used for isomer-specific analysis of these toxic chemicals. In this work, we investigated the possibility of discriminating among the isomeric precursors of chlorinated aromatic compounds by charge inversion mass spectrometry using an MS/MS instrument. Charge inversion mass spectra using Cs, K, and Na targets were measured for C6H4Cl2+ ions produced from the ortho-, meta-, and para-isomers of dichlorobenzene (C6H4Cl2). The charge inversion mass spectra were found to display a clear dependence on the nature of the isomeric precursors for each of the targets used. The clear discrimination among the isomers of dichlorobenzene achieved using charge inversion mass spectrometry in the present work indicates that most of the C6H4Cl2+ ions obtained by electron impact retain the structure of the parent molecules, demonstrating the potential utility of this technique for isomer-selective microanalysis of various pollutants.
English
J. Mass Spectrom. Soc. Jpn., 49(6), 224-226, 2001
The formation and the fragmentation of the sodium adduct ions for tertiarybutoxycarbonyl-L-prolyl-L-proline ethyl ester (Boc-L-Pro-L-Pro-OEt) were compared with those for Boc-D-Pro-L-Pro-OEt on the addition of sodium chloride in positive-ion fast atom bombardment (FAB) mass spectrometry. The abundance of the [M+Na]+ ion was about 2 times lower than that of the [M+H]+ ion on the addition of sodium chloride in FAB mass spectrum for Boc-L-Pro-L-Pro-OEt, while the former was almost same as the latter in the spectrum for Boc-D-Pro-L-Pro-OEt, suggesting that Boc-D-Pro-L-Pro-OEt has a stronger Na+ ion affinity than Boc-L-Pro-L-Pro-OEt. On the other hand, in the collision-induced dissociation (CID) mass spectra of the [M+Na]+ ions, the abundance of the [M+Na-C(CH3)3+ H]+ ion, which is due to the loss of a tertiarybutyl group from the [M+Na]+ ion for Boc-D-Pro-L-Pro-OEt, was higher than that for Boc-L-Pro-L-Pro-OEt. These results indicate that Boc-L-Pro-L-Pro-OEt was distinguished from Boc-D-Pro-L-Pro-OEt by the CID mass spectra of the [M+Na]+ ions, and the difference of the cleavage patterns between Boc-L-Pro-L-Pro-OEt and Boc-D-Pro-L-Pro-OEt when the carboxyl-terminals were protected with ethyl ester, was smaller than that between tertiarybutoxycarbonyl-L-prolyl-L-proline (Boc-L-Pro-L-Pro) and Boc-D-Pro-L-Pro when they were free reported previously.1)
Japanese, English Abstract
J. Mass Spectrom. Soc. Jpn., 49(6), 227-228, 2001
A new design of TOF mass spectrometer with helical orbit is described. Six 60° cylindrical electric sector fields are arranged in a circular shape with six free spaces of length RE. At one free space, after one turn of ions through electric sectors, a parallel shift of ion trajectory is obtained in the y-direction (parallel to the axis of helical ion orbit) by a pair of parallel plate condensers which generate deflection fields in opposite directions. Then ions are injected into the lower orbit of electric sector. Helical orbit of many turns is realized by successive parallel shift. In this way, very long ion path length is obtained in a small geometrical space. Excellent focussing nature is attained in both time and space. The ion beam spread in y-direction is minimized by the focussing nature of parallel plate condenser.
Japanese, English Abstract
J. Mass Spectrom. Soc. Jpn., 49(6), 229-236, 2001
Intensive studies on highly charged ions (HCIs) have been recently performed by using electron beam ion traps (EBITs). General property of HCIs and principle of the ion source are outlined. Details of the Tokyo-EBIT installed at the University of Electro-Communications are described with several experimental results.
Japanese, English Abstrarct
J. Mass Spectrom. Soc. Jpn., 49(6), 237-240, 2001
For a higher sensitivity, the parameters of liquid chromatography-mass spectrometry-selected ion monitoring (LC-MS-SIM) using atmospheric pressure chemical ionization (APCI) were examined. The scan-range means the range of atomic mass unit which was scanned at the center of an established value. The sampling-point-number means the number of measurement points within the scan-range. The counting-number means the number of the data acquisition per measurement point. The area and height of a peak as sensitivity, the full width half maximum (FWHM) and the actual scan-time which was required for the scanning were measured. The plant hormone, indole-3-acetic acid (IAA) was used as a standard chemical. The suitable parameters for higher sensitivity on the measurement limit level were as follows: 1) The scan-time might correspond to the value of FWHM. 2) The counting-number was over about 7,000. 3) The scan-range might correspond to a decimal fraction of the molecular weight of the sample substance. The results showed that the value obtained from repeated sampling-point-number was a total amount, that the value obtained from repeated counting-number was a mean and that there were no loss of time on repetitions of the sampling-point-number and the counting-number.
Japanese, English Abstract
J. Mass Spectrom. Soc. Jpn., 49(6), 241-243, 2001
The "in-gel" digestion followed by peptide mass fingerprint is an innovative method of identifying the proteins separated by one- or two-dimensional polyacrylamide gel electrophoresis. It is now widely used in various applications in proteomics, e.g., differential display of proteins in specific biological conditions, or exhaustive identification of the components that physically interact in a protein complex. In this NOTE, the standard procedures including silver-staining and in-gel digestion are described, and the peptides derived from skin keratins that are often mixed in the process are listed.
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