The amino acid sequence in tripeptides and tetrapeptides has been analyzed by DADUMIKE and B/E-'linked stun ' spectrometry, as well as by collisional activation in the first and second field free region of a mass spectrometer embodying the inverse Nier-Johnson geometry. Collisional activation enhances the intensity of fragment ions. Einleitung. -Schon seit langerer Zeit wird die Massenspektrometrie in der Peptidanalytik eingesetzt. Die Aminosauresequenz von Oligopeptiden lasst sich damit an kleinen Substanzmengen ermitteln [ l ] [ 2 ] . In Peptidenwie in anderen Polymeren -I wiederholt sich ein Grundstrukturelement periodisch; das fuhrt zu einer Periodizitat in der massenspektrometrischen Fragmentierung. Entsprechende ionisierte Fragmente lassen sich im konventionellen Massenspektrum nachweisen. Oft sind aber diese wichtigen, sequenzcharakteristischen Ionen nicht leicht zu erkennen, da sie durch Signale konkurrenzierender Fragmentierungen uberdeckt werden. Neue Wege eroffnete die DADI/MIKE-Spektrometrie'), weil damit genetische Beziehungen zwischen einem Ion und dessen Folge-Ionen nachgewiesen werden [3] [4]. Auf diese Weise lassen sich auch sequenzcharakteristische Fragment-Ionen aus Oligopeptiden selektiv verfolgen. Die genetische Reihenfolge und die Masse dieser ausgewahlten Ionen fuhren zur Aminosaure-Sequenz des untersuchten Oligopeptides [5]. Eine solche Analyse lasst sich grundsatzlich auch an unreinen Proben [6] oder an Peptid-Gemischen [7] durchfuhren.

No abstract

The @E= constant linked scan is shown to be an excellent tool for quantifications with reversed geometry mass spectrometers. Deuterium-labelled analogues may be used as internal standards, thus providing very simple clean-up procedures. The principle is demonstrated with the example of chloro-substituted benzoic acid methyl esters. Possible interferences arising from isotope peaks are discussed. The method is applied to the quantification of caffeine in beverages.

Phenol and live acydic isollleric compounds have been investigated using electron impact and 6eld ionization tedmiqms, mass panlysed ion kinetic energy spectrometry and dlision induced dissociation mass analysed ion kinetic energy speehometry. The ldnetic energy release data corresponding to the elimination of earbon monoxide from the molecular ions sbow that at least two stmetmes of the reactant ion are involved. The electron impact and h i d ionization coilision induced dissociation mass analysed ion kinetic energy spectra indicate that d e r eleetron impact conditions, the phenol ion partially isomerizes to another ion stroctnre. An isomerization of about 40% to the stroctme of cfs-2-hexen-4-p-l-ai is in good accordance with the spectral data.

The constant B2E linked scan is shown to be an excellent tool for the profiling of biogenic amines in wine samples. The fragment ion at m/z 169 of the dansylated amines is used for the precursor ion search in combination with direct sample evaporation. Besides the profile a semi-quantification may be achieved when using suitable amines as internal standards with standard deviations of 12-17%. More accurate results with standard deviations of 3-5% are obtained when using deuterated analogues as internal standards. Both methods are applied to the analysis of biogenic amines in synthetic mixtures and actual wine samples.