Qualitative and quantitative analysis of carbonyl compounds in ambient air samples by use of an HPLC–MSn method

The suitability of HPLC combined with ion-trap mass spectrometry was studied for the determination of carbonyl-2,4-dintrophenylhydrazones in ambient air. MS quantification was based on two internal standards and atmospheric pressure chemical ionization in the negative-ion mode. Limits of detection for air samples of 750 L in the full-scan mode varied between 1 and 15 ng x m(-3) expressed as carbonyl. Limits of quantification were approximately a factor of three higher. This is sufficient for background regions. For sample volumes of 750 L air the instrument response was linear from 10 ng x m(-3) to 800 microg x m(-3) for carbonyls and from 3 ng x m(-3) to 250 ng x m(-3) for dicarbonyls. Besides complete method validation, quantitative results for six air samples from four background sampling sites in North and Central Europe were compared with those obtained by use of HPLC-UV. Thirty-six carbonyl compounds could be identified and twenty-four were quantified. Values for major compounds, i.e. those present at levels well above the UV detection limits (9 to 18 ng x m(-3)), deviated by less than 20%.     

Über den Zusammenhang zwischen Struktur und integraler Intensität der (υCN)-Schwingung in Palladium-cyanid-, -cyanomethanid- und -β-cyanoethenid-Komplexen

On the Connection between Structure and Integrated Intensities of the n?(C?N) Vibration in Palladium Cyanide, Cyanomethanide, and β-Cyanoethenide Complexes Integrated intensities of n?(C?N) mode in palladium cyanide, cyanomethanide and β-cyanoethenide complexes and related mercury compounds have been determined in solid state (KBr disks) or in solution. The intensities in cyanide complexes are a measure for the extent of metalcyanide π-bonding, whereas in cyanomethanide and cyanoethenide complexes they reflect the metalcarbon σbonding polarity. The influence of ? C?N…?M in bridged complexes is discussed with respect to intensity of n?(C?N) vibration. For the types of compounds studied, structural unit integrated intensities are characteristic data.     

Determination of nitrated polycyclic hydrocarbons in aerosols using capillary gas chromatography combined with different electron capture detection methods

A method is described which allows the determination of subnanogram concentrations of mono- and dinitrated polyaromatic hydrocarbons with two to four ring systems in aerosol samples. High performance liquid chromatography is used to separate the nitro compounds from other classes of substances. Carbozoles elute in the same fraction. Both electron capture detection and negative ion chemical ionization mass spectrometry combined with capillary gas chromatography are used for quantification. Use of these two methods leads to a considerable improvement of selectivity and sensitivity for nitrated compounds. In contrast to the situation with a nitrogen-sensitive detector, carbazoles do not interfere and detection limits in the order of 10–200 pg/m³ are possible. The applicability of the method is critically discussed. Determination of nitrated polyaromatic hydrocarbons in aerosol samples from an aluminum smelter serves as an example.     

Large sample injection method (≥ 100 μL) for capillary GC using a commercial thermodesorption unit as injection device

A commercial thermodesorption and cold trap unit can be used as a large sample volume injection device in high resolution gas chromatography. Volumes of more than 100 μl can be injected. More than 97% of solvents, such as hexane, can be removed by a Tenax TA precolumn without any loss of compounds with volatilities comparable to naphthalene. Experimental conditions, recovery rates of polycyclic aromatic hydrocarbons, and the reproducibility of the method are described in detail. The method was successfully applied for the determination of PAH in air particulate matter extracts.     

Selective determination of substituted PAH in aerosols using liquid CO2-extraction,HPLC prefractionation on chemically activated silica,and HRGC combined with negative ion mass spectrometry

A method is described which allows the determination of different substituted polycyclic aromatic hydrocarbons (PAH) such as NO₂-PAH, carbazoles, keto-PAH, and aza-arenes in aerosol samples. Liquid CO₂-extraction is used to minimize the loss of reactive compounds. High performance liquid chromatography on chemically activated silica is employed to prefractionate the samples into subfractions with a minimum of overlap between different PAH compound classes. Both electron capture detection and negative ion chemical ionization combined with capillary gas chromatography are used for identification and quantification. The latter method also allows distinction between isomers with different toxic properties when N₂O/CH₄ reaction gas mixtures are used. Selectivity for tetrachlorodibenzo-p-dioxins as against pesticides and polychlorinated biphenyls can be improved by this technique. The applicability of the method is critically discussed and different examples are given.     

Evaluation of four mass spectrometric methods for the gas chromatographic analysis of polychlorinated n-alkanes

The suitability of four mass spectrometric methods for the gas chromatographic analysis of polychlorinated n-alkanes (PCAs, also called chlorinated paraffins) was evaluated and compared using spiked and fish liver samples. Electron ionization tandem mass spectrometry (EI-MS/MS) as well as electron capture negative ionization (ECNI) combined with low and high resolution mass spectrometry and CH4/CH2Cl2-negative ion chemical ionization (NICI) low resolution mass spectrometry were investigated. All methods showed an accuracy of <21% for the analysis of spiked fish samples. However, the analysis of real samples showed deviations of up to 46% between the four mass spectrometric methods. The influence of the selected reference standard on quantification was also evaluated. The use of a quantification standard with a degree of chlorination deviating from that of the sample can result in differences of > 100% for the ECNI methods. EI-MS/MS and CH4/CH2Cl2-NICI led to errors of maximum 17% and 33%, respectively, independent from the degree of chlorination of the used reference standard.     

Vibrational relaxation of liquid benzene. A temperature-dependent Raman lineshape study of the selectively deuterated molecules

The halfwidths of the symmetric CH and CD stretching modes of liquid C₆H₆, C₆D₆, sym-C₆D₃H₃, p-C₆H₂D₄, p-C₆H₄D₂, C₆HD₅, and C₆H₅D are reported. Their temperature dependence is measured in nearly the whole liquid range. There is no coincidence with present relaxation theories.     

Direkt-potentiometrische Konzentrationsbestimmungen mit ionensensitiven Elektroden unter Verwendung komplexierender Hilfsreaktionen

Zusammenfassung Die Grundlagen der direkt-potentiometrischen Konzentrationsbestimmung von Anionen und Kationen werden beschrieben, für die keine ionensensitiven Elektroden bekannt sind. Es wird die Konzentrationsabnahme eines Hilfsions gemessen, das mit dem analytisch zu bestimmenden Ion einen stabilen Komplex bildet.Ausführliche Angaben werden zur Bestimmung von Al³⁺ mit F^– als Hilfsion und von Ni²⁺ mit CN^– als Hilfsion gemacht. Auf die prinzipiellen Möglichkeiten einer Bestimmung von Fe²⁺, Fe³⁺, Au⁺, Hg²⁺, Th⁴⁺, Zr⁴⁺, UO₂ ²⁺, SCN^– und S₂O₃ ^2– wird eingegangen.

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Direct-potentiometric determinations with ion-sensitive electrodes using complexing auxiliary reactions

The basic principles of the direct-potentiometric determination of several cations and anions are discussed, for which no ion-sensitive electrode is available. The decrease in concentration of an auxiliary ion is measured which forms stable complexes with the ion to be determined. Detailed information is given on the determination of Al³⁺ with F^– as auxiliary ion and of Ni²⁺ with CN^– as auxiliary ion. An outlook is presented on the possible determinations of Fe²⁺, Fe³⁺, Au⁺, Hg²⁺, Th⁴⁺, Zr⁴⁺, UO₂ ²⁺, SCN^– and S₂O₃ ^2–.

     

2,4,6-Tri-tert.butylphenyl-substituierte Silane

2,4,6-Tri-tert.butylphenyl Substituted Silanes 2,4,6-Tri-tert.butylphenyl lithium reacts with trimethoxysilane, triethoxysilane, and triphenoxysilane to give the dialkoxy- or diphenoxy-(2,4,6-tri-tert.butylphenyl)-silanes Ar? SiH(OR¹)₂ 3 ? 5 (Ar = 2,4,6-tri.tert.butylphenyl, R¹ = Me, Et, Ph). Interaction of methyl lithium or n-butyl lithium with 3 – 5 leads under partial or complete substitution of the OR¹-functions to the silanes Ar? SiH(OR¹)R² 7 – 11 and Ar? SiHR₂² 12 and 13 (R² = Me, Bu). Reaction of 3 with lithium tert.butul-amide gives tert.butylamino-methoxy-(2,4,6-tri-tert.butylphenyl)-silane 14 . 5 is reduced by LiAlH₄ to 2,4,6-tri-tert.butylphenyl-silane 6 . The reaction of 3 with antimony trifluoride results in formation of 2,4,6-tri-tert.butylphenyl trifluorosilane 2 . Attempts to replace the alkoxy or phenoxy groups in 3 – 5 by chlorine led under silion carbon bond cleavage to 1,3,5-tri-tert.butylbenzene.     

Über die Reaktion des Tris-(trimethylsilyl)-silyllithiums mit Aceton

On the Reaction of Tris-(trimethylsilyl)-silyl Lithium with Acetone Depending on the reaction conditions tris-(trimethylsilyl)-silyl lithium interacts with acetone to give 2-[bis-(trimethylsilyl)-silyl]-2-[tris-(trimethylsilyl)-silyl]-propane 2 or 2-[bis-(trimethylsilyl)-silyl]-2-(trimethylsioxy)-propane 4 , resp. The formation of 2 and 4 as a result of a 1, 3-Si, O-trimethylsilyl shift is discussed. The structure of 2 , which is characterized by strong restrictions of rotation about the C? Si(SiMe₃)₃ bond, is proved by nmr spectra as well as by conversion of 2 into 2-[chloro-bis-(trimethylsilyl)silyl]-2-[tris-(trimethylsilyl)silyl]-propane 3 .