Trace-level determination of pesticides in food using difficult matrix introduction-gas chromatography-time-of-flight mass spectrometry

A procedure for the fully automated analysis of food samples by means of difficult matrix introduction-gas chromatography-time-of-flight mass spectrometry (DMI-GC-ToF MS) is discussed. After extraction, samples require very little clean-up and are injected in a micro- or micro-vial which is held in a liner. Next, the liner is placed in the injector and the contents of the vial are thermally desorbed and led directly to the capillary GC column. After GC-ToF MS analysis, the data are processed automatically using a peak deconvolution algorithm. The practicability of the procedure was demonstrated by analysing spiked grape and pineapple samples down to the 1-10 ng/g concentration level.     

A new suzuki-heck-type coupling cascade: indeno[1,2,3]-annelation of polycyclic aromatic hydrocarbons

Under palladium catalysis, o-bromobenzeneboronic acid can be coupled with 1-bromonaphthalene (6) and with oligocyclic bromoarenes to furnish indeno-annelated polycyclic aromatic hydrocarbons 1-4 and 25 in a single operation in moderate to good yields (27-87%). Alternatively, o-dibromoarenes and 1,2-dibromocycloalkenes can be cross-coupled with 1-naphthaleneboronic acid under the same conditions to yield analogous products (6-87%), and indenocorannulene (19) can be prepared likewise in a single step from pinacol corannuleneboronate (18) (40%).     

EPR-spektroskopische Untersuchung von Kaolin Caminau,seiner Entwässerungsprodukte sowie der Chlorierungs-produkte des Metakaolins

EPR Studies of Caminau Kaolin, its Heating Products, and of the Chlorination Products of Metakaolin EPR-spectra of kaolin, metakaolin and of the heating and chlorination products of metakaolin have been measured and partially interpreted. Fe³⁺ ions are found in kaolin in at least five different coordination conditions. Coordination changes of Fe³⁺ ions by heating kaolin and tempering metakaolin are reflected sensitively in the EPR spectra. Correlations between EPR spectra of the solid not fluidable chlorination residues and chlorination conditions have been found.     

Integral representations for the alternating groups

We show that every complex representation of an alternating group can be realized over the ring of integers of a ``small' abelian number field.

     

Methylation with sodium naphthalenide for the analysis of substituent distribution of trimethylsilyl celluloses and their evaluation

The substitution pattern of trimethylsilyl celluloses silylated withhexamethyldisilazane and N,N-dibutylamino­trimethylsilane was determined bymethylation analysis. Methylation with sodium hydride/methyl iodide wasaccompanied by significant desilylation because sodium hydride is alwayscontaminated with sodium hydroxide. Sodium naphthalenide prepared in tetrahydrofuran under anhydrous reaction conditions alloweda reduction of the extent of desilylation to less than 10 percent. In allcases preferred silylation of the 6-position was found. Celluloses silylatedwith hexamethyldisilazane and N,N-dibutylaminotrimethylsilane had almostidentical substituent distributions. Lower reaction temperature resulted inhigher regioselectivity.