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English
J. Mass Spectrom. Soc. Jpn., 48(6), 373-379, 2000
A new method is proposed for elimination of artifacts appearing in deconvolution of electrospray ionization mass spectra, where two algorithms, a partial correlation method (PCM) and a sub-harmonic artifact removal filter (SHARF), are used. In addition to the elimination of artifacts, the former algorithm removes influence of singly charged ions generated from contamination in a sample, while the latter algorithm removes influence of background noises and baseline offsets in a measured spectrum. The proposed method results in supplying the deconvoluted spectra free from artifacts with good signal-to-noise ratios and without distortion on peak shapes. Applications to some bio-molecules lead to the conclusion that our method is especially useful for analyses of their mixture samples, which show complicated mass spectra.
English
J. Mass Spectrom. Soc. Jpn., 48(6), 380-386, 2000
Chiral recognition of the host-guest complexations between the (RRRR)-18-crown-6-tetracarboxylic acid (18C6TCA) host (H) and a-amino acid or their ester derivative guests (G) has been systematically determined using both FAB mass spectrometry (MS) and capillary zone electrophoresis (CE). A comparison of these two techniques for the same series of guests was then done for the first time. In the case of 18C6TCA, we found that there is no correlation between the chiral recognition obtained from FABMS (i.e., the IRIS value) and from CE (i.e., the a value in an aqueous buffer solution) covering three sets of guests including amino acids, amino acid esters, and primary aromatic amines. On the other hand, the former showed a good agreement with that from NMR (i.e., the KR/KS value; the ratio of the corresponding equilibrium constants), supporting our earlier conclusion that FABMS is a good measurement tool for predicting differences (DDG° values) in the respective chiral H-G interactions in solution. We also found that when a given guest changes from an amino acid to its corresponding amino acid ester, the a value by CE dramatically changes from a > 1.0 to a < 1.0, though the IRIS value by FABMS does not show any such changes. These findings were considered to be due to the characteristic contributions of the dissociable host's COOH functions under the experimental pH conditions in CE
English
J. Mass Spectrom. Soc. Jpn., 48(6), 387-394, 2000
For precise determination of carbon isotope ratios of individual polycyclic aromatic hydrocarbons (PAHs), optimum condition to separate PAHs from unresolved complex mixture (UCM) extracted from environmental samples were examined. Two stationary phases, three eluents, and four flow rates were tested using an automatic solid-phase extraction system. PAHs standard and motorbike soot extract were used as testing sample. The results indicated (1) aminopropylsilane stationary phase (NH2 s.p.) is superior to cyanopropylsilane stationary phase (CN s.p.), (2) n-hexane/benzene is superior to n-hexane and n-hexane/dichloromethane as the eluent, and (3) 0.03 mL min-1 of flow rate is the most suitable. By the separation procedure with 1 g of the NH2 s.p., approximately 75% of UCM extracted from soot sample is found to elute in fraction 1; phenanthrene, anthracene, fluoranthene, and pyrene are in fraction 2; and the PAHs heavier than chrysene are obtained as fraction 3. In the case of environmental samples such as a lake sediment and an aerosol sample, UCM interfering isotope measurement of co-eluted PAHs was not observed in fractions 2 and 3. Thus, this procedure can be applied to d13C measurement of PAHs over "3-ring" in environmental samples containing UCM with a precision of 1.2%o. Reproducible elution condition is obtained by using a computerized separation system. No significant carbon isotopic fractionation of PAHs was observed during this separation procedure.
Japanese, English Abstract
J. Mass Spectrom. Soc. Jpn., 48(6), 395-400, 2000
Discussion on the spectral mass resolution is made on an orthogonal acceleration time-of-flight mass spectrometer, which consists of a two-stage acceleration and a one-stage reflecting mirror, coupled with an atmospheric pressure ionization technique. Even though taking the second order space focusing as well as the turn-around effect into account, the mass resolution is lowered by the influence of several optical parameters such as the diameter of the orifice located after an external ion source, the beam deflection by a grid, and the charging-up voltage in an ion storage. It is found that both the charging-up effect and the beam deflection by the grid located in the two-stage ion acceleration region can be corrected in some extent by selecting a suitable mirror voltage. However, the most influential parameter is the beam diameter at an orifice. This influence on the mass resolution cannot be corrected.
English
J. Mass Spectrom. Soc. Jpn., 48(6), 401-403, 2000
The C3H7O+ (m/z 59) ions produced from nine precursors are differentiated into six (or seven) groups by measuring their collision-induced dissociation spectra versus collision energy (CID curve), using a quadrupole ion trap mass spectrometer.
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