Development of a headspace GC/MS analysis for carbonyl compounds (aldehydes and ketones) in household products after derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine.

Carbonyl compounds (aldehydes and ketones) are suspected to be among the chemical compounds responsible for Sick Building Syndrome and Multiple Chemical Sensitivities. A headspace gas chromatography/mass spectrometry (GC/MS) analysis for these compounds was developed using derivatization of the compounds into volatile derivatives with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA). For GC/MS detection, two ionization modes including electron impact ionization (EI) and negative chemical ionization (NCI) were compared. The NCI mode seemed to be better because of its higher selectivity and sensitivity. This headspace GC/MS (NCI mode) was employed as analysis for aldehydes and ketones in materials (fiber products, adhesives, and printed materials). Formaldehyde was detected in the range of N.D. (not detected) to 39 microg/g; acetaldehyde, N.D. to 4.1 microg/g; propionaldehyde, N.D. to 1.0 microg/g; n-butyraldehyde, N.D. to 0.10 microg/g; and acetone, N.D. to 3.1 microg/g in the samples analyzed.     

Lead tetraacetate oxidation of 3-amino-9-cyanazuleno[2,1-d]triazole and 1-amino-9-cyanazuleno[1,2-d]triazole. A novel oxidative cleavage of aminotriazole ring

Either 1-amino-4-cyanazuleno[2,1-d]triazole or 3-amino-4-cyanazuleno-[1,2-d]triazole reacts with lead tetraacetate in dichloromethane to give the unexpected ring cleavage product, 1,8,8-tricyanoheptafulvene in good yield instead of the expected 1-cyano-2,3-dehydroazulene.     

Thermodynamic and conformational properties of partially butyralized poly(vinyl alcohol) in aqueous solution

Phase separation behavior has been studied in aqueous solutions of partially butyralized poly(vinyl alcohol) (BuPVA) with various degrees of butyralization x_Bu and various molecular weights. It is found that these systems exhibit both upper and lower critical solution temperatures. The theta temperatures θ_LCST, evaluated by means of Shultz–Flory plots, are found to be 25.1, 23.3, and 14.4°C for BuPVAs with x_Bu of 7.5, 9.9, and 12.7 mol %, respectively. The unperturbed dimension 〈R²〉₀/M is evaluated as ca. 1.2 × 10^?16 Ų in the above range of x_Bu from viscosity measurement at θ_LCST. Properties of the BuPVA solutions are compared with those of other PVA copolymers.     

Indirect conductimetric detection of cyclodextrins in liquid chromatography

Indirect conductimetric detection of cyclodextrins (CDs) was investigated in liquid chromatography (LC). The mobile phase contained an electrolytic substance which maintained high background, and CDs were indirectly detected owing to a depression of the background signal due to dilution of the mobile phase by the analyte molecules. The dynamic reserve, defined as the ratio of the background to its noise level, was (1–2) × 10⁵, and the detection limits at S/N = 3 were 23–40 ng for CDs when a microcolumn LC system was employed.     

Theoretical and experimental examination of near-field acoustic levitation

A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.     

Determination of traces of copper and silver in tantalum metal by anodic stripping voltammetry

Summary Nanogram quantities of copper and silver are electrodeposited on a glassy carbon electrode from a hydrofluoric-nitric acid solution containing 0.5–1 g of tantalum. The deposit is then anodically removed in 0.1M hydrochloric acid, a current-voltage curve being recorded. The impurities at the parts per billion level in high-purity tantalum metal powder are determined within 3 hours.

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Zusammenfassung Nanogrammengen Kupfer und Silber werden aus flußsaurer, salpetersaurer Lösung von 0,5–1 g Tantal elektrolytisch an einer Elektrode aus glasartigem Kohlenstoff abgeschieden. Während der anodischen Auflösung in Salzsäure wird eine Stromspannungskurve geschrieben. Verunreinigungen in der ppb-Größenordnung in hochreinem Tantalpulver lassen sich so innerhalb 3 Stunden bestimmen.