SummaryA novel fused silica capillary GC/MSdirect coupling is described which ensures quantitative transfer of sample from the point of injection to the ion source of a mass spectrometer without contacting any surfaces other than the column wall. This device permits GC analysis of highly labile substances. Aflatoxin 61, previously considered unassayable by GC, can now be determined by GC/MS.

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.

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.

A new, commercially available digital linked scan unit mass display/macker is presented operating in real time in a mass range of 0.0 to 1638.3 u without the need for a data system. The prerequkites and limitations of successful linked scans with their consequences for the new design are discussed. Examples give evidence of the need for increased accuracy. INTRODUCI'ION ~~Linked scans and mapping techniques are well-known means of establishing the fragmentation pathway of ions outside the ion source. Parent ion search experiments at a given daughter ion mass m2 and daughter ion search experiments at a given parent ion mass ml have both been successfully used in mixture analysis and structure elucidation.' More recently, constant neutral loss scans have been introduced. They allow the search for ions fragmentating by loss of a given uncharged mass Am.2*3 These scans are especially useful in mixture analysis when looking for ions with identical functional group^.^ Thus, linked scans on double focusing sector type mass spectrometers now offer possibilities of using MS/MS techniques, which are typically performed by the more complex triple stage instruments. Limitations exist however, arising mainly from the parameters varied by the scans, the geometry of the mass spectrometer and the possible occurrence of artefact peaks.The mass number of singly charged ions rn* transmitted in standard in-focus spectra ( E = E,, V = V,) defines a convenient measure for the magnetic field B.If exclusively singly charged ions are assumed, the daughter ions of dissociations outside the ion source will only be transmitted by the magnetic sector at m* = m22/m1. Examples are the well-known metastable peaks arising from dissociations within the field free region (FFR) preceding the magnetic field. They are observed in single focusing and conventional geometry double focusing mass spectroscopy. In general m* is not sufficient to deduce m,, m2 and Am. The observation of better defined diffuse peaks is, however, possible with double focusing instruments, preferably by linked scans varying B and the electric sector voltage E simultaneously, according to suitable scan laws. The acceleration voltage V, thereby remains constant in order to avoid detuning of the ion source and unnecessary limitation of the range of observable m a~s e s .~ Daughter ions m2 arising from dissociations in the first field free region (FFR1) in between the accelerating field (ACCF) and the first sector field and, on instruments of reversed geometry, from dissociations within WR2, the region in between the two sector fields, are thereby detected. These ions are transmitted by the electrostatic analyser (ESA) with reduced E at E/E, = mJm, due to the loss of mass and hence of energy. The two instrument-independent quantities m" and E/E, characterize the location of diffuse peaks and allow the determination of m,, m2 and Am. The preselection of any of these three masses restricts the location of expected diffuse peaks to a corresponding line on the m*-E/Eo plane (Fig. 1). ...

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