Application of a liquid chromatography tandem mass spectrometry method to the analysis of water-soluble vitamins in Italian pasta

A sensitive and selective liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the determination of several water-soluble vitamins, namely vitamins B₁, B₂, B₆ (pyridoxine, pyridoxal, and pyridoxamine), and PP (nicotinamide and nicotinic acid), pantothenic acid, and folic acid was developed and validated. The analytes were characterized by means of their electrospray (ESI) and atmospheric pressure chemical ionization (APCI) mass spectra. In general, the positive ion spectra were 100- to 1000-fold more intense than the corresponding negative ion ones. Chromatography of water-soluble vitamins was obtained by using a reversed-phase C16 Amide (15 cm, 5 μm) column and a mobile phase made of ammonium formate buffer (20 mM, pH 3.75)/methanol under gradient elution conditions. Linearity of the MS response was observed over three to four orders for both ESI and APCI, and limits of detection were in the low μg/l range for both the ionization techniques. In particular, the sensitivity of ESI was about two- to five-fold higher for all vitamins except PP vitamers, for which APCI produced a better response. Precision calculated at two concentration levels (0.05 and 1.0 mg/l) was within 0.2-7.4% for all intra- and inter-day determinations and for all analytes. The LC-ESI-MS/MS method was applied to the quantitative analysis of the natural content of vitamins in typical Italian pasta samples, as well as in fortified pasta samples produced for the US market.     

Biological application of microelectrode arrays in drug discovery and basic research

Electrical activity of electrogenic cells in neuronal and cardiac tissue can be recorded by means of microelectrode arrays (MEAs) that offer the unique possibility for non-invasive extracellular recording from as many as 60 sites simultaneously. Since its introduction 30 years ago, the technology and the related culture methods for electrophysiological cell and tissue assays have been continually improved and have found their way into many academic and industrial laboratories. Currently, this technology is attracting increased interest owing to the industrial need to screen selected compounds against ion channel targets in their native environment at organic, cellular, and sub-cellular level.As the MEA technology can be applied to any electrogenic tissue (i.e., central and peripheral neurons, heart cells, and muscle cells), the MEA biosensor is an ideal in vitro system to monitor both acute and chronic effects of drugs and toxins and to perform functional studies under physiological or induced pathophysiological conditions that mimic in vivo damages. By recording the electrical response of various locations on a tissue, a spatial map of drug effects at different sites can be generated, providing important clues about a drug's specificity.In this survey, examples of MEA biosensor applications are described that have been developed for drug screening and discovery and safety pharmacology in the field of cardiac and neural research. Additionally, biophysical basics of recording and concepts for analysis of extracellular electrical signals are presented.Abbreviations AP action potential - DG dentate gyrus - EC entorhinal cortex - ECG electrocardiogram - ERG electroretinogram - LFP local field potentials - MEA microelectrode array - PSTH peri-stimulus–time histogram - SNR signal-to-noise ratio     

Über einige nebenprodukte der thermolyse von bis(trimethylsilyl)-diimin

In the course of decomposition of bis(trimethylsilyl)diimine (BSD), which leads mainly to five products, the tris(trimethylsilyl)hydrazyl radical is formed among other intermediates. This radical reacts with hydrogen donors HR (e.g. HR = solvent) to tris(trimethylsilyl)hydrazine and radicals ·R, which on the other hand react further with BSD to by-products of BSD thermolysis. The types of these by-products and mechanisms of their formation are discussed. The thermolysis of BSD in toluene, for example, produces tris- and bis(trimethylsilyl)benzylhydrazine and bis(trimethylsilyl)benzalhydrazone.     

Trivalent‐Intermediate Valent Cerium Ordering in CeRuSn – A Static Intermediate Valent Cerium Compound with a Superstructure of the CeCoAl Type

New equiatomic stannide CeRuSn was synthesized from the elements by arc‐melting. CeRuSn was investigated by X‐ray powder and single crystal diffraction: C2/m, a = 1156.1(4), b = 475.9(2) and c = 1023.3(4) pm, β = 102.89(3)°, wR2 = 0.0466, 1229 F² values and 38 variables. CeRuSn adopts a superstructure of the monoclinic CeCoAl type through a doubling of the subcell c axis. In the superstructure two crystallographically independent cerium sites occur. Based on the interatomic distances the two sites can be assigned to trivalent Ce2 and intermediate valent Ce1. This trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements χ_m(T): below 150 K χ_m, measured with decreasing temperature, follows a Curie‐Weiss law χ_m = C_m/(T–θ_p) giving C_m = 0.38 emuK/mol as Curie constant per CeRuSn mol; a value showing that only half of the cerium atoms are trivalent in CeRuSn (C_m = 0.807 emuK/mol for one free Ce³⁺ ion). A remarkable feature of the CeRuSn structure are the short Ce1–Ru1 (233 pm) and Ce1–Ru2 (246 pm) distances. The crystal chemistry of CeRuSn is discussed on the basis of a group‐subgroup scheme.     

Gas chromatographic enantiomer separation of agrochemicals and polychlorinated biphenyls (PCBs) using modified cyclodextrins

The enantiomers of the polychlorinated polycyclic xenobiotics heptachlor, cis- and trans-chlordane, cis- and trans-heptachlorepoxide, oxychlordane, and bromocyclen have been resolved by gas chromatography with selectively substituted cyclodextrins. The order of elution of these compounds and of α-hexachlorocyclohexane (α-HCH) was determined by comparison with enantiomerically enriched reference compounds obtained by preparative enantioselective gas chromatography. A separation of the eight stereoisomers of the pyrethroid insecticide allethrin into seven peaks was achieved. Both trans-diastereomers were separated into their enantiomers and the order of elution could be determined by comparison with commercially available (S)-bioallethrin and trans-bioallethrin. Also one cis-diastereomer was separated, wheras the other cis-isomer could not be resolved. In addition 15 out of 19 stable atropisomeric polychlorinated biphenyls with 5, 6 and 7 chlorine substituents, some chiral organophosphorus pesticides, including acephate and malaoxon and the herbicide bromoacil were separated.     

Gasdurchlässigkeit von gummielastischen Werkstoffen für Stickstoff

Zusammenfassung Es wird über Messungen der Gasdurchlässigkeit von gummielastischen Werkstoffen für Stickstoff berichtet. Der Gasdurchtritt von Stickstoff durch gummielastische Materialien ist ein Permeations- oder Lösungsdiffusionsvorgang. Die Theorie der Permeation wird dargelegt, und zwei Methoden zur Auswertung von Permeationsmessungen werden angegeben. Nach Beschreibung der Meßanordnung wird an Hand von einigen grundsätzlichen Messungen der Gasdurchlässigkeit von gummielastischen Werkstoffen für Stickstoff gezeigt, daß es sich hier tatsächlich um einen Lösungsdiffusionsvorgang handelt; d. h. dasFicksche Diffusionsgesetz und dasHenrysche Löslichkeitsgesetz sind erfüllt, und die Diffusion ist der geschwindigkeitsbestimmende Vorgang. Die Betrachtung der Temperaturabhängigkeit der Permeation zeigt, daß man für Diffusionskoeffizient, Löslichkeitskoeffizient und Permeationskoeffizient jeweils eine Aktivierungsenergie angeben kann. Meßergebnisse, die an einer Vielzahl von gummielastischen Werkstoffen erhalten wurden, werden mitgeteilt.Mit 11 Abbildungen und 2 Tabellen     

Phosphoniumsalze mit Hydrogendihalogenidanionen HCl2−, HBr2− Hl2− oder HBrCl−

Phosphonium Salts with Hydrogen Dihalide Anions HCl₂^?, HBr₂^?, HI₂^?, or HBrCl^? Phosphonium hydrogen dihalides [R₃PR′][XHY] (X = Y = Cl, Br, I; X = Br, Y = Cl) resp. [R₃PH]HBr₂ are obtained as extremely hydrolyzable crystals by reaction of phosphonium halides or tertiary phosphanes with hydrogen halide. According to IR spectroscopic results the solid compounds mostly contain anions [XHX]^? with symmetric hydrogen bonds. In solution ¹H NMR measurements show a slight (X = Cl, Br) or considerable (X = I) dissociation according to HX₂^? ? X^? + HX. On heating the solid compounds decompose with formation of hydrogen halide and [R₃PR′]X or [R₃PH]X. In this process the hydrogen bromidechlorides [R₃PR′][BrHCl] exclusively eliminate HCl. NMR studies (¹H und ³¹P) with solutions containing [R₃PH]HBr₂ (R = phenyl, 1-naphtyl) or HBr and Ph₃P in varying molar ratios show that a fast proton exchange between the competing Lewis bases R₃P and Br^? exists.     

Zur Theorie der Polynomringe

Let \(\mathfrak{B}\) be a variety of rings,R a ring of \(\mathfrak{B}\) andx an indeterminate. The free compositionR(x, \(\mathfrak{B}\) ) ofR and the free algebra of \(\mathfrak{B}\) generated byx, is called the \(\mathfrak{B}\) -polynomial ring inx the variety of rings, rings with identity, commutative rings or commutative rings with identity resp. We prove some results about relations between the polynomial ringsR(x, \(\mathfrak{B}\) ), whereR is fixed and \(\mathfrak{B}\) runs over these varieties. Moreover we construct normal form systems for certain polynomial ringsR(x, \(\mathfrak{B}\) ).     

The injection and the projection theorem for spectral sets

For a closed normal subgroupN of a locally compact groupG view a closed subset of Prim_* L ¹ (G/N) as a subsetE of Prim_* L ¹ (G) in the canonical way and writeN for Prim_* L ¹ (G/N) as a subset of Prim_* L ¹ (G); then the injection theorem says: IfE is spectral (i.e. of synthesis), then is so; and if andN are spectral, thenE is too. In case of a group of polynomial growth with symmetricL ¹-algebra, where smallest idealsj (E) with given hulls exist, it is known thatN is always spectral. For a closed,G-invariant subsetF of Prim_* L ¹ (N) define a closed subsetE of Prim_* L ¹ (G) by . Denote by e (I') the ideal generated byC ₀₀ (G)*I', where theG-invariant idealI' ofL ¹ (N) is viewed as a subset of measures onG, then the projection theorem states: IfE is spectral, thenF is so, and ifF is spectral withe (j (F))=j (E) thenE is spectral. All assumptions are fulfilled for instance, ifG andN are of polynomial growth with symmetricL ¹-algebra and eitherSIN-groups or solvable.