摘要:

Current-reversal chronopotentiometry was used to measure the rates of decomposition of tertiary alkyl radical anions. Radical ions studied were chosen to yield both constrained and unconstrained products (e.g., 1-nitroadamantylvs.t-nitrobutyl) in an effort to illuminate the effect that such structural differences might have upon the decay rates. Temperature studies were performed to yield thermodynamic details; supporting electrolyte concentration changes and three solvents were employed to explore ion pairing effects.

ISSN:0003-2719    

DOI:10.1080/00032718708064598

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Modification of an anion-exchange membrane by (1-(2-arsono-phenylazo))-2-hydroxy-3,6-naphthalenedisulfonic acid (thoron) results in a membrane that can chelate metals. The high affinity of the disulfonate for the anion-exchange sites together with molecular adsorption of the aromatic thoron onto the polymers yields a system that is stable in strong acids at or below 1 M. By employing a relatively high pH sample (5-9) in conjunction with an acidic stripping solution (0.2 - 1.0 M HCl), uphill transport of Cu(II) and Zn(II) was accomplished. The transport rate was increased by means (lower chelating capacity and the use of a chelate-forming aid on in the stripping solution) of promoting the volume diffusion mechanism of membrane transport. With a 0.05 mmol per dry gram chelating capacity and a 0.1 M EDTA stripping solution (pH 6.5), an enrichment factor of 16 was observed in a one-hour experiment with a 200 mL sample, 11 cm2membrane, and 5 mL stripping solution. This value compares favorably with those obtained by other uphill transport modes under the same conditions.

ISSN:0003-2719    

DOI:10.1080/00032718708064599

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Paper chromatographic behaviour of some pesticides and toxicants has been studied using impregnated papers in various organic and inorganic solvents. Several binary and ternary separations have been achieved which were not possible on plain papers. Method developed can be successfully applied for certain isomeric differentiation. The minimum detection limit was found to be 25 to 50 mole of the test substance.

ISSN:0003-2719    

DOI:10.1080/00032718708064600

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The response of polycyclic aromatic hydrocarbons (PAH) at different UV wavelengths was measured using high performance liquid chromatography with spectrophotometric diode-array detection. By utilizing the total UV absorption bandwidth (200-400 nm), it was found that a narrow distribution of normalized response factors (area/g) could be obtained for 16 PAH in a reference mixture of frequently-occurring species, even though the PAH represented a wide variety of different chromophores.

ISSN:0003-2719    

DOI:10.1080/00032718708064601

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A liquid chromatography system is directly coupled to a moderate power helium microwave induced plasma for the selective determination of no metals in aqueous solutions. The detector is a large volume helium microwave-induced plasma operated at 500 watts with a helium support gas flow of 21L/min. A sample set of halides and oxohalgen salts are separated by ion exchange chromatography and introduced into the plasma as mist generated with an ultrasonic nebulizer. Detection limits range from 1.5 to 6 μg. Calibration plots are presented. Selectivity is observed when monitoring the elemental signals of co-eluting peaks.

ISSN:0003-2719    

DOI:10.1080/00032718708064602

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The photodecompositions of five typical metal dithizonates have been studied in various solvents under the irradiation of 310-nm UV light and ordinary indoor illumination. In methylene chloride and chloroform the decomposition mechanism is confirmed to be the interaction of these metal dithizonates and the oxidants arising from the photodecomposition of the solvent. In carbon tetrachloride the decompositions were fast and were observed to be first-order in the dithizonates. In benzene, no apparent photodecoraposition was found. Since these solvent effects are independent of the metal, benzene is probably the best solvent for the extraction-spectrophotometry of unstable dithizonates.

ISSN:0003-2719    

DOI:10.1080/00032718708064603

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new formulation of the Konig colorimetric method for cyanide is selective, has increased stability, and is sensitive to a few ppb. The formulation can be placed as a strip on the safety seals of bottles to indicate tampering, placed in a syringe and used to sample head space gas in commercial products or liquids to test for tampering, or placed in the desiccant container in bottles of capsules or tablets. Reaction with head space gas requires just a few seconds, and less than an hour is required if the cyanide must first permeate through capsules. Liquids also can be either drawn directly into the syringe, or the cyanide evolved by adding an Alka-seltzer tablet to purge the gas. Reactions are immediate. Hydrogen sulfide and ammonia which interfere with several other cyanide tests, do not interfere with this formulation. A mixture of N-chlorosuccinimide and succinimide oxidizes CN-to CN+. The cyanogen ion selectively reacts with 4-phenylpyridine to form a dialdehyde, which is then coupled with either barbituric acid (red rapidly turning to blue) or 3-methyl-l-phenyl-2-pyrazolin-5-one (purple slowly turning to green black).

ISSN:0003-2719    

DOI:10.1080/00032718708064604

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

While the use of robots in routine quality-control and sample-preparation procedures is well established, their use in the research laboratory has not received as much attention. In order to evaluate the performance of laboratory robots in investigating problems that are non-routine and slightly more difficult, a Zymate-I robot was adapted to investigate the kinetics of two well-characterized reactions. The problems encountered and the need for verification devices in laboratory robotics are discussed.

ISSN:0003-2719    

DOI:10.1080/00032718708064605

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A response function (RF) in order to simultaneously optimize different variables by the SIMPLEX method in FIA systems, with the possibility of applying weights, is proposed. The optimization program developed to use this RF is assayed in the optimization of two different flow injection procedures. The obtained results are discussed.

ISSN:0003-2719    

DOI:10.1080/00032718708064606

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A fluorimetric method for the determination of plasma cortisol has been studied in detail. The method is based upon reaction with ethanol-sulphuric acid reagent and measurement of the produced fluorescence at exc. 470 and em. 550 nm. Some modifications were suggested regarding extraction solvent and time of the reaction. Under the proposed conditions, the method is rapid and a sensitivity of 1.5 μg/100 ml was attained. It was applied on 29 patients with chronic renal failure and 12 normal subjects. Cortisol levels at 8 AM in patients on either haemodialysis (27.05 ± 8.94 μg/100 ml) or under conservative treatment (45.13 ± 10.68 μg/100 ml) were significantly higher (P < 0.001) than control group (16.12 ± 3.45 μg/100 ml).

ISSN:0003-2719    

DOI:10.1080/00032718708064607

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor