Rapid Communications in Mass Spectrometry

doi: 10.1002/rcm.1290071201pmid: N/A

doi: 10.1002/rcm.1290071221pmid: N/A

Okamoto, Masahiko; Takahashi, Ken‐ichi; Doi, Tadashi

doi: 10.1002/rcm.1290071202pmid: N/A

A liquid chromatography/thermospray ionization tandem mass spectrometry (LC/TSP‐MS/MS) method was developed for the quantification of abscisic acid (ABA) in crude plant extracts without derivatization. By this technique interfering chemical background ions are eliminated and a detection limit for ABA olf 0.2 ng is achieved. Reproducibility for quantification is attained by parallel reaction monitoring of ABA and added ABA‐d6 used as an internal standard. The standard curve is linear over the range 200 pg to 10 ng of injected ABA. As examples of the application of the methodology, the quantification of ABA in some plant tissues is given.

Cairns, Thomas; Luke, Milton A.; Chiu, Kin S.; Navarro, David; Siegmund, Emil G.

doi: 10.1002/rcm.1290071203pmid: N/A

Previous studies using the ion trap as a potential replacement for an array of element‐sensitive detectors indicated that only semi‐quantitative results at the 50–100 ppb range could be obtained for 245 pesticides because of interfering endogenous sample matrix compounds. The development of a new clean‐up procedure for a wide range of fruits and vegetables, specifically for use in an ion trap, has been undertaken to improve recoveries at the low ppm level to within analytically acceptable ranges (80–120%). This clean‐up involved the use of three solid‐phase extractions. The use of a C‐18 SepPak column removed the majority of hydrocarbon‐like molecules while the anion‐exchange column (QMA) removed all colored compounds and flavors, and finally the use of an aminopropyl column removed all sugars. Preliminary results from this study using 24 selected pesticides in four different sample matrices have indicated an acceptable improvement over previous results.

Fujimaki, Susumu; Kudaka, Ichiro; Sato, Tetsuya; Hiraoka, Kenzo; Shinohara, Hisanori; Saito, Yahachi; Nojima, Kazutetsu

doi: 10.1002/rcm.1290071204pmid: N/A

Negative‐ion electrospray mass spectrcmetry for the detection of higher fullerene anions is discussed. The fullerenes were reduced in dimethoxyethane/aromatic solvent using NaK amalgam and analyzed by electrospray ionization mass spectrometry using a double‐focusing mass spectrometer. All the C n− ions (n = 2k, and k is an integer) could be detected up to n = 102 except for 60 < n < 70 and n = 72. The detection efficiency of C76 is found to be considerably lower than that for C78, probably because the C 76− ion reacts further in solution and is converted to undetectable reaction products. In addition to the fullerene anions, large peaks due to methoxy‐substituted fullerene anions, Cn(OCH3) m−, are observed. The intensities of these ions grow with time.

Grossenbacher, H.; Märki, W.; Coulot, M.; Müller, D.; Richter, W. J.

doi: 10.1002/rcm.1290071205pmid: 8280917

Two congeners Q4 and Q5 inferred in earlier analyses to be cyclic succinimide‐type dehydration product; of recombinant hirudin (variant 1) were structurally fully characterized. After isotopic labeling by ring‐opening with H218O, the suspected anhydro‐positions Asp53 and Asp33 were confirmed by tandem mass spectrometry (MS/MS) sequencing of relevant smaller peplides directly in the enzymatic hydrolysates (V8 protease) using electrospray MS/MS. The chosen strategy proved highly efficient and sensitive.

Kenny, Donald V.; Callahan, Patrick J.; Gordon, Sydney M.; Stiller, Steven W.

doi: 10.1002/rcm.1290071206pmid: N/A

For the first time, molecular ions from two different compounds have been simultaneously isolated in an ion‐trap mass spectrometer and their subsequent tandem mass spectra (MS/MS) obtained. Isolation was achieved by applying a filtered‐noise field (FNF) to the end‐caps of a FinniganMAT ion‐trap mass spectrometer (ITMS) using the Teledyne MEC/Hitachi HST‐1000 Enhancement Kit. The HST‐1000 generates a broadband waveform that would normally eject all ions from the trap. However, by setting notches in the waveform that correspond to certain resonant frequencies, individual masses can be isolated and stored in the trap without the need for the conventional DC voltage on the ring electrode. Using this FNF technique, the molecular ions of p‐dichlorobenzene (m/z 146) and 1,3,5‐trimethylbcnzene (m/z 120) were simultaneously isolated from a 42‐component mixture of volatile organic compounds. Each molecular ion was collisionally dissociated by applying a resonance excitation (‘tickle’) voltage from the HST‐1000, and the spectrum for each molecular ion was obtained by scanning the RF voltage to the ring electrode.

Duncan, Mark W.; Matanovic, Gabrijela; Cerpa‐Poljak, Anne

doi: 10.1002/rcm.1290071207pmid: 8280918

Internal standards were used to demonstrate that matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry can be applied to the quantitative analysis of low molecular weight polar compounds. Three examples were tested: a standard curve for 3,4‐dihydroxyphenylalanine (DOPA) was prepared using a stable isotope analogue (i.e., [13C6]DOPA) as an internal standard; [2H16]‐acetylcholine was employed as an internal standard for the quantification of acetylcholine; and in the final example, the peptide Ac‐Ser‐Ile‐Arg‐His‐Tyr‐NH2 was used as an internal standard for the quantification of the peptide H‐Ser‐Ala‐Leu‐Arg‐His‐Tyr‐NH2. In each instance, straight line fits (r2>0.95) demonstrate that MALDI is a viable approach for the quantitative analysis of low molecular weight analytes.

Ioanoviciu, D.

doi: 10.1002/rcm.1290071208pmid: N/A

The resolution of single‐ and double‐stage, homogeneous electric mirror time‐of‐flight mass spectrometers can be calculated with the derived formulae for detectors located normally to the ion flight direction or parallel to the mirror face. These formulae account for contributions to the peak width from ion initial velocity and position in the source (‘turn around’ time included), from ion‐packet longitudinal and transverse size at the source final grid, as well as due to the angular ion spread. Third‐order terms are included for beam size, angular aperture and velocity spread, the incidence angle being small. The field‐free space needed to obtain energy focusing in time is connected with the length of the accelerating space inside the source.

New, Anthony P.; Haskins, Neville J.; Games, David E.

doi: 10.1002/rcm.1290071209pmid: N/A

The aim of this work was to probe the stereochemistry of a series of monosaccharides. Firstly, the underivatized sugars were investigated using linked‐scans and tandem mass spectrometry on a ‘hybrid’ instrument (hybrid MS/MS) and secondly, a comparison of linked‐scan and hybrid MS/MS was carried out on the butyl and phenyl boronate di‐esters. In situ derivatization of the sugar to the boronate di‐ester allows a negative‐ion fast‐atom bombardment (FAB) investigation with greater sensitivity than for the underivatized sugar. The linked‐scan data allow a great deal of information on the structure and chemistry of the sugars to be obtained, but the sensitivity at lower mass is limited. The hybrid MS/MS data give similar fragmentation information, plus improved sensitivity at lower molecular weight.