Fractional Square Functions and Potential Spaces, Ⅱ

In this paper, we study fractional square functions associated with the Poisson semigroup for Schrdinger operators. We characterize the potential spaces in the Schrdinger setting by using vertical, area and g*λ fractional square functions.     

Rotating disk sorptive extraction of triclosan and methyl-triclosan from water samples

A method of sample preparation based on use of rotating disk sorptive extraction (RDSE) has been developed for determination of triclosan (TCS) and methyl-triclosan (MTCS) in water samples. The sorptive and desorptive behavior of the analytes was studied by use of a rotating disk coated with polydimethylsiloxane (PDMS) on one of its surfaces. Chemical and extraction behavior were studied to establish the best conditions for extraction. The optimum conditions for both analytes were: sample volume 25 mL, pH?4.5, NaCl concentration 6 % (w/v), disk rotational velocity 1,250 rpm, and extraction time 80 min. A desorption time of 30 min was used with 5 mL methanol. The detection limits for TCS and MTCS were 46 and 34 ng?L^?1, respectively. Recovery was evaluated at two concentrations, 160 and 800 ng?L^?1, and the values obtained were between 80 and 100 %. The method was applied to analysis of influent water at two treatment plants in Santiago, Chile.     

On-line ion-exchange preconcentration in a flow injection system coupled to capillary electrophoresis for the direct determination of UV absorbing anions

On-line ion-exchange preconcentration, performed in a flow injection analysis system, has been integrated with capillary electrophoresis via a specially designed interface, and a sensitive and selective method for the determination of nitrite, nitrate, bromide and iodide using direct UV absorbance detection has been developed. Fivefold enrichment of these aforementioned anions can be realised. Separation conditions such as carrier electrolyte and concentration of electroosmotic modifier were investigated. Limits of detection were ca. 10 ng ml⁻¹ for nitrite and nitrate in aqueous samples, and the overall relative standard deviation was about 5%.     

A slightly shorter route to carbocyclic nucleosides. Synthesis of (±)-trans-1-[2-(hydroxymethyl)cyclopentylmethyl]uracil

(±)-trans-1-[2-(Hydroxymethyl)cyclopentylmethyl]uracil ( 1 ) was prepared in two steps and 56% yield from 2-hydroxymethylcyclopentylmethylamine (7) and 3-methoxy-2-propenoylisocyanate ( 6 ). Isocyanate 6 was prepared from methyl 3-methoxy-2-propenoate in four steps and 38% overall yield.     

N‐Chloro­acetyl‐β‐alanine

The β‐alanine residue of the title compound, C₅H₈ClNO₃, has a ggt folded conformation, which is mainly stabilized through intermolecular N—H⋯O=C (amide–acid) and O—H⋯O=C (acid–amide) hydrogen bonds. In addition, a cis conformation is found for the Cl—CH₂—C(=O)—NH torsion angle, which is associated with the presence of an intramolecular hydrogen bond.     

Uranium determination at ppb levels by X-ray fluorescence after its preconcentration on polyurethane foam

A sensitive method based on the preconcentration of uranium on powdered polyurethane foam (PUF) has been developed to determinate this element in water samples by X-ray florescence. Uranium at ppb levels was sorbed as the salicylate complex on powdered PUF at pH 4.0. The resulting PUF was filtered through a filter paper and used for X-ray fluorescence measurements. For 50 μg/l of uranium the coefficient of variation for five measurements is 5% and the detection limit is 5.5 μg/l. The interference level of various ions and ligands was studied and optimum conditions were developed to determine uranium in reference materials, waste water, mine drainage, and sea water.     

Diorganotin(IV) compounds derived from n‐methyl‐2,2′‐diphenolamine and 2,2′‐diphenolamine

The reaction of N‐methyl‐2,2′‐diphenolamine 1 and 2,2′‐diphenolamine 2 with some diorganotin(IV) oxides [R1/2SnO: R¹ = Me, n‐Bu, t‐Bu and Ph] led to the syntheses of diorgano[N‐methyl‐2,2′‐diphenolato‐O,O′,N]tin (IV) 3–6 and diorgano[2,2′‐diphenolato‐O,O′,N]tin (IV) 7–9 . All compounds (except 7 ) studied in this work were characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, infrared, and mass spectroscopy. Their ¹¹⁹Sn NMR data show that the tin atom is tetracoordinated in CDCl₃ but penta and hexacoordinated in DMSO‐d₆. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 133–139, 1999     

Syntheses and characterization of new (2S)-2-hydroxy-1,4-oxazin-3-ones derived from β-aminoalcohols

The reactions of methyl glyoxylate hemiacetal 1 with 2-(methylamino)ethanol 2 , (1R,2S)-(–)-ephedrine 3 and (1S,2S)-(+)-pseudoephedrine 4 provide the (2S)-2-hydroxy-1,4-oxazin-3-ones 2a , 3a , 4a in good yield. They were characterized by ¹H, ¹³C, NMR, and infrared and mass spectroscopy. The structures of 2a and 3a were established by X-ray diffraction. The configuration of C₂ (S) is demonstrated by ¹H NMR data and confirmed for compounds 2a and 3a by single-crystal X-ray diffraction studies. © John Wiley & Sons, Inc.