Determination of trace amounts of p-toluenesulfonic acid in organic materials

Summary p-toluenesulfonic acid is separated from the sample (e. g. glucose, glycollic acid, lactic acid, lactose, maltose) by extraction using liquid ion-exchanger Alamine 336 (tricaprylamine) and quantitated by liquid chromatography. Precision at the 5 ppm level characterized by a standard deviation is 0.458 ppm. Recoveries average 66.13% forp-toluenesulfonic acid determination in glucose, and 71.99% in glycollic acid. Calibration curves constructed by the aid of spiked samples are linear in the region studied, i. e. 1.4–13.3 ppm and can be used for evaluation in routine analysis. When only an occasional check for the presence ofp-toluenesulfonic acid is needed, one spiked sample is analyzed as a reference standard.

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Zusammenfassung p-Toluolsulfonsäure (I) läßt sich von Glucose, Glykolsäure, Milchsäure, Milchzucker, Malzzucker u. dgl. durch Extraktion mit dem flüssigen Ionenaustauscher Alamin 336 (Tricaprylamin) abtrennen und chromatographisch bestimmen. Die Genauigkeit bei 5 ppm entspricht einer Standardabweichung von 0,458 ppm. Bei Bestimmung von I in Glucose findet man durchschnittlich 66,13% der eingesetzten Menge, bei Bestimmung in Glykolsaure 71,99%. Die mit Hilfe von Bezugsproben, denen bekannte Mengen von I zugesetzt wurden, ermittelten Eichkurven verlaufen im untersuchten Bereich, d. h. zwischen 1,4 und 13,3 ppm linear und können im Routinebetrieb verwendet werden. Bei nur gelegentlicher Bestimmung von I bedarf es nur einer Vergleichsprobe als Bezugs-Standard.

     

An Efficient Synthesis of (±)-α-Spirovetivene and Related Compounds

A process for the synthesis of (±)-α-spirovetivene starting from I-oxo–2-carbethoxy-6, 10-dimethyl spiro[4.5]dec-6-ene(I)¹ is described. The oxo group of I was reduced by the process of Coates², and the resulting spiro ester (III) and spiro alcohol (IV) were transformed to (±)-α-spirovetivene by the process of Uijttewaal³ and by conventional methods.     

Valence electron orbitals of an oligo(p-phenylene-ethynylene)thiol on gold

This communication reports measurement of one-photon (21.2 eV) and one-color, two-photon (3.2-4.5 eV) photoemission spectra of 4,4'-bis-(phenylethynyl)benzenethiol chemisorbed on gold. Four features are observed in these spectra: two occupied, predominantly molecular levels below the Fermi level and two unoccupied, predominantly molecular levels above the Fermi level. The occupied and unoccupied bands closest to the Fermi level are assigned to delocalized pi-bands, and the other occupied and unoccupied bands, to localized pi-bands. With this assignment, the hole- and electron-injection barriers and the transport gap for those levels are deduced.     

Comparison of reversed-phase column materials for high-performance liquid chromatography of proteins

Nine reversed-phase materials with various bonded phases from different suppliers were studied for the separation of hydrophilic proteins with two solvent systems. Protein retention, resolution and recovery were not correlated with the nature of the hydrocarbonaceous ligand. Peak volumes increased with molecular weight, which led to broad, irregular peaks for the larger proteins on some columns. Four columns that performed equally well were selected for the purification of hydrophobic Sendai virus membrane proteins. In this case, more distinct differences were found between columns. Recovery of the membrane proteins strongly depended on the combination of column and solvent systems.     

Magnetic resonance imaging of pediatric spinal dysraphism

Thirty pediatric patients with spinal dysraphism were studied with magnetic resonance imaging. A variety of dysraphic anomalies were visualized, including syringohydromyelia, tethered cord, widened spinal canal, meningomyelocele, lipomyelomeningocele, lipomeningocele, intraspinal lipoma, congenital dermal sinus tract, and scoliosis. In 29 of 30 cases, MRI diagnostically visualized spinal cord and dysraphic anatomy. A combination of T1-weighted sagittal and axial imaging planes provided the most complete visualization. In specific cases, T2-weighted examinations were useful in demonstrating likely regions of inflammation bordering infected sinus tracts. MRI demonstrates a wide variety of dysraphic spinal anomalies and effectively screens children for occult spinal dysraphism.     

MRI of the skull

Thirty-four patients with a wide variety of benign and malignant incidental skull findings on routine magnetic resonance (MR) imaging of the brain were reviewed. In most instances detection of the lesions was not difficult. However, recognition of various patterns of skull involvement in different disease processes is important. This is particularly true in differentiating benign from malignant lesions, which may be a critical factor in patient management.     

Triangles and Triads

Triangles provide a valuable means of diagrammatically summarizing and understanding data upon triads. In this paper, various properties of the triangular representation of data are discussed. The paper focuses on data relating to parliamentary elections, and demonstrates that an analysis based on the use of transition matrices can be misleading, especially when based upon what is referred to as a ‘proportional loss’ model. A triangular presentation of voting data suggests an alternative analysis-namely, a model of uniform change. Finally, there is discussion of some of the consequent implications for the marketing strategy of individual political parties.