Dieter Henneberg

Open split connection of glass capillary columns to mass spectrometers

SummaryAn open split-type connection is described with a platinum capillary as the inlet line to the mass spectrometer. This connection device is suited to various types of columns, but especially for glass capillaries. Advantages of the open split are (i) a rather high yield, (ii) high flexibility with regard to column parameters, and (iii) optimal reliability, because the open split requires no vacuum-tight seal of the column to the spectrometer and no special geometry of the column end. An additional feature is the possibility of suppressing very large (solvent) peaks.

Eine Kombination von Graschromatograph und Massenspektrometer zur Analyse organischer Stoffgemische

ZusammenfassungDas Austrittsgas eines Gaschromatographen wird kontinuierlich einem Massenspektrometer zugeführt. Das Massenspektrometer ist fest auf eine Masse eingestellt. Es dient als spezifischer Detektor, mit dem man je nach Wahl der festen Masse Stoffe identifizieren oder zu bestimmten Verbindungsklassen zuordnen kann. Außerdem sind quantitative Aussagen über gaschromatographisch nicht getrennte Gase oder Verbindungen möglich.

Siscom — a new library search system for mass spectra

Abstract SISCOM is a library search system for mass spectrometry which is based on a new method of coding spectra by selecting the most important peaks within homologous ion series, and on a multiple factor assessment of the result. Examples demonstrate the ability of the system to identify various compounds, even from mixtures or by reference spectra which differ from those measured. SISCOM is especially suitable for detecting structural similarities like common substructures, even in cases where no similarity can be recognized by visual comparison of patterns or by human interpretation of the spectrum.

High-performance gas chromatograph—mass spectrometer interfacing: investigation and optimization of flow and temperature

Abstract A new version of an open-split type of gas chromatograph-mass spectrometer interface with a glass restriction has been developed, with particular emphasis upon the use of glass capillary columns. A flow of scavenger gas is provided in the interface, which at low flow-rates avoids “dead volume tailing” of large peaks and which at high flow-rates dilute peaks that are too strong. The influence of both the interface and the ion source on chromatographic performance has been investigated with high-polarity and low-volatility test compounds. The interface proved to be effective but adsorption, mainly in the ion source, restricts the range of application in modern high-temperature gas chromatography. Experiments with a platinum capillary as a restriction and experience in producing and mounting glass capillaries in the new interface favour the use of glass restrictions.

Optimization of search algorithms for a mass spectra library

Abstract The SISCOM mass spectra library search is mainly an interpretative system producing a “hit list” of similar spectra based on six comparison factors. This paper deals with extension of the system; the aim is exact identification (retrieval) of those reference spectra in the SISCOM hit list that correspond to the unknown compounds or components of the mixture. Thus, instead of a similarity measure, a decision (retrieval) function is needed to establish the identity of reference and unknown compounds by comparison of their spectra. To facilitate estimation of the weightings of the different variables in the retrieval function, pattern recognition algorithms were applied. Numerous statistical evaluations of three different library collections were made to check the quality of data bases and to derive appropriate variables for the retrieval function.

Addition von organomagnesium-verbindungen an nichtaktivierte CC-doppelbindungen : V. Intramolekulare cyclisierung von 4-alkenyl-magnesiumhalogeniden zu cyclobutylderivaten

Abstract The primary reaction products of the addition of 3-methyl-2-butenylmagnesium chloride to 1-octene are partially converted to cyclobutyl derivatives of magnesium by intramolecular metalC addition to the CC double bond in 4-position.

Analyse von i-Paraffingemischen aus „methylene insertion“- bzw. „methylene-d2 insertion“-Reaktionen mit einer Kombination Capillar-Gas-Chromatographie/Massenspektrometrie

SummaryBy insertion of CH2 and CD2 respectively into hydrocarbons preferably of the branched type in the C8 to C12 range mixtures of isomeric hydrocarbons are obtained, which can only be separated with capillary columns. The correlation of the peaks was done independently by means of their Kovats retention indices or the corresponding index increments and from the pattern of the mass spectra measured within a capillary column-fast scan-mass spectroscopy combination. The rules governing the retention behaviour and the fragmentation pattern of the mass spectra of isomeric hydrocarbons — together with the information which can be drawn from the statistical course of the insertion reaction — allow a reliable identification of the different hydrocarbon species. The identification method described is expected to be extended also to more complicated hydrocarbon mixtures.ZusammenfassungDie Kombination Capillar-Gas-Chromatographie/Massenspektrometrie wurde auf die Analyse von i-Paraffingemischen angewendet. Es ergab sich sowohl mit Regeln über das Retentionsverhalten als auch über die Korrelation von Massenspektren eine Erweiterung und Verfeinerung des bisher Bekannten. Die Anwendung derselben Methodik wird vermutlich auch die schwierige Analytik von anderen Kohlenwasserstoffmischungen befördern.

Radiation Chemistry of Carbohydrates, X* γ-Radiolysis of Crystalline D-Glucose and D-Fructose

α-D-Glucose and β-D-fructose were γ-irratiated in the solid (polycrystalline) state at room temperature at doses of 3.5 · 1020-4.2 · 1021 eV g-1 (dose rate 1.16 · 1018 eV g-1 min-1). Carbohydrate products containing ≤ 6 carbon atoms were identified and their G-values (in parentheses) measured. Glucose: Dihydroxyacetone (1) (0.05), 3-deoxy-tetrose (2) (0.015), 1,4-dideoxy-2-pentulose (3) (0.05), 2,4-dideoxy-pentose (4) (0.085), 2,4-dideoxy-pentonic acid (5), 2,3-dideoxypentos-4-ulose (6) (together 0.035), threose (7), erythrulose (8), erythrose (9), erythronic acid (10) (together 0.04), 1-deoxy-2-pentulose (11) (0.005), 2-deoxy-ribose (12) (0.25), 3-deoxy-pentosulose (18) (0.02), 3,5-dideoxy-hexonic acid (14) (0.02), 2,3-dideoxy-hexonic acid (15) (0.01), arabinose (16) (0.25), ribose (17), ribonic acid (18) (together 0.02), 2-deoxy-2-C-hydroxymethyl-pentonic acid (19) (0.06), 5-deoxy-gluconic acid (20), 2deoxy-5-keto-glucose (21), 2-deoxy-gluconic acid (22), 2-deoxy-3-keto-glucose (28), 3-deoxy-glucosone (24), 3-deoxy-gluconic acid (25), 3-deoxy-4-keto-glucose (26), 3-deoxymannonic acid (27) (together 0.4). Identified but nor measured quantitatively were glucosone (28), 3-keto-glucose (29), 4-keto-glucose (30), 5-keto-glucose (31) and gluconic acid (82). G(H2) = 5.75; G(CO2) = 0.7. Fructose: 7-9 (together 0.65), 3-deoxy-pentonic acids (37), 3-deoxy-pentosulose (88) (together 0.3), arabonic acid (89) (0.1), 18 (0.05), 6-deoxy-2,5-hexodiulose (40) (40). Identified but not measured quantitatively were glyceraldehyde (34), butanone-(3)-diol-(1,2) (35) and 2- and 3-deoxy-hexodiuloses. G(H2) = 4.75, G(CO2) = 0.05. Reaction schemes are proposed to account for the formation of the products. The scission of the hemiacetal bond and of the C-Η and C-C bonds next to it appears to be typical for solid state irradiations. The formation of deoxy-compounds is observed both in the solid state and in aqueous solution. The formation of dideoxy-compounds is only prominent in the solid state. In polycrystalline fructose a chain reaction is induced leading to 6-deoxy-2,5-hexodiulose (40).

Radiation Chemistry of Carbohydrates, VI: γ-Radiolysis of Glucose in Deoxygenated N2O Saturated Aqueous Solution

In the γ-radiolysis of deoxygenated N2O-saturated aqueous solutions of D-glucose (10-2 M, 1 · 1019 - 4 · 1019 eV/g, dose rate 4.3 · 1018 eV/g · h at 25°C), the following products have been identified: Gluconic acid (1), 2-deoxy-gluconic acid (2), arabinose (3), 2-deoxy-ribose (4), 5-deoxy-gluconic acid (5), glucosone (6), 3-deoxy-glucosone (7), 3-keto-glucose (8), [2-deoxy-3-keto-glucose (9), 4-deoxy-3-keto-glucose (10)]3, 4-ketoglucose (11), 3-deoxy-4-keto-glucose (12), 5-deoxy-4-keto-glucose (13), 5-keto-glucose (14), 2-deoxy-5-keto-glucose (15), 4-deoxy-5-keto-glucose (16), 6-deoxy-5-keto-glucose (17), gluco-hexodialdose (18), 5-deoxy-xylo-hexodialdose (19), ribose (20), xylose (21), erythrose (22), threose (23), 3-deoxy-pentulose (24), 2-butanone-(1,4)-diol (25), and dihydroxyacetone (26). G-values were also determined. In the primary processes OH radicals and H atoms from the radiolysis of the solvent water abstract carbon bound hydrogen atoms from D-glucose to give all six possible primary glucosyl radicals. The observed products are formed in disproportionation reactions of the primary glucosyl radicals (1, 6, 8, 11, 14, 18) or of sugar radicals which originate from the primary glucosyl radicals by water elimination (2, 4, 7, 9, 10, 12, 13, 15, 16, 17, 19), rearrangements (5, 14, 15), or loss of carbon monoxide (3, 4, 20). Products 1-5 and probably 20 have primary glucosyl radicals with the odd electron at C-1 as precursors. Radicals with the free spin at C-2 give rise to the products 6 and 7. Attack at C-3 yield products 8-10, at C-4 products 11-13, at C-5 products 14-17, and an attack at C-6 products 18 and 19. Products 21-26 are formed in very low yields and hence are of minor importance. Their mechanism of formation has not been investigated.

Ein kleines Massenspektrometer als spezifischer gaschromatographiseher Detektor

SummaryThe application of a small mass spectrometer as a detector for gas chromatography with variable selectivity in combination with capillary columns is described. A flame ionisation detector was used as independent detector. The following examples demonstrate the practical use of a mass-spectrometric detector for qualitative and quantitative analysis: 1. Identification and determination of lead alkyls with methyl, ethyl and butyl groups in petrols. 2. Identification of trimethyl silylethers of the general formula Me3Si-O-R (R=alkyl, aryl) in a complex mixture.ZusammenfassungEs wird der Einsatz eines kleinen Massenspektrometers als gaschromatographischer Detektor mit variabler Selektivität in Verbindung mit Capillarsäulen beschrieben. Als unabhängiger Detektor wurde ein Flammenionisationsdetektor benutzt. An folgenden Beispielen wird die Leistungsfähigkeit dieser Kombination demonstriert: 1. Selektiver Nachweis und quantitative Analyse von Bleialkylen mit Methyl-, Äthyl- und Butylgruppen in Benzinen; 2. Selektiver Nachweis von Trimethylsilyläthern Me3Si-O-R mit R=Alkyl, Aryl in komplizierten Mischungen.