摘要:

A simple and fast metal extraction method that combines closed vessels and microwave heating for the simultaneous extraction of ten selected heavy metals (As, Cd, Co, Cr, Hg, Mn, Ni, Pb, Zn) from marine sediments is proposed. Digestion conditions, i.e. power and times microwave irradiation. reagent extractant, sample amount, were optimized to recover the potentially available metallic fraction not bound in silicates. A nitric acid and two step microwave program was established. The resulting solutions were analyzed by flame (FAAS), hydride generation (HGAAS) and cold vapour (CV-AAS) atomic absorption spectrometry. Quantifications were made using direct calibration with aqueous standards. The recoveries of the spiked samples investigated ranged from 89 to 113 %. The results obtained from analyzing the BCR certified reference sediment CRM 277 Estuarine Sediment were in good agreement with the certified values (93–105%), except for low values for chromium (79%). The relative standard deviations for the determination of metals were less than 4%. Finally, the technique designed herein was applied to sediment samples from La Coruña estuary, NW Spain.

ISSN:0003-2719    

DOI:10.1080/00032719908542604

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The separation of the enantiomers of nomifensine maleate, a psychotropic drug, were investigated using achiral and chiral stationary phases Three stationary phases were studied for their ability to separate the enantiomers: reversed phase cyanopropyl with a chiral mobile phase additive; inclusion (cellulose tris 3,5-dimethylphenyl carbonate (chiracel OD); and brush/pirkle type (S-tert-leucine, (R)-1-(α-naphthyl) ethylamine (Sumichiral OA-4700). Changes in mobile phase composition were studied to determine the effect of solvents on the separation of the enantiomers. Baseline separations were achieved for nomifensine enantiomers under isocratic conditions on the cyanopropyl column with 90:10 v/v 0.1% triethylamine-acetonitrile pH 4.0 (adjusted by trifluoroacetic acid) containing 10 mM β-cyclodextrin, on a Chiracel OD column using hexane-absolute methanol (96:4 v/v), and on a Sumichiral OA-4700.column using hexane-dichloroethane-absolute ethanol-trifluoroacetic acid (100:12.5:8.5:0.1v/v/v/v). The flow rates were 0.8 mL/min with detection at 292 nm.

ISSN:0003-2719    

DOI:10.1080/00032719908542605

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple and elegant extractive separation method for trace level rubidium has been developed using dibenzo-24-crown-8 from picric acid medium. Rubidium was quantitatively extracted from 0.0006 – 0.05 M picric acid with 0.0006 – 0.01 M dibenzo-24-crown-8 in nitrobenzene as a diluent. From the organic phase rubidium was quantitatively stripped with 1–10 M HNO3, 1–8 M HBr, 0.5–10 M HCl and 10 M HClO4. Rubidium was estimated by flame emission spectroscopy at 780 nm. Separation of rubidium was carried out from number of binary mixtures. Most of the elements from s-block, p-block & d-block showed high tolerance limits. It was possible to separate rubidium from associated elements in multicomponent mixtures. The method was extended for the determination of rubidium in various rock samples.

ISSN:0003-2719    

DOI:10.1080/00032719908542606

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Highly selective ion analysis of sub-ppm Pb(II) on a porous graphitic carbon (PGC) column, is described using ion chromatography with acidified aqueous mobile phases, post-column detection using PAR and spectrophotometric detection. Sensitivity is enhanced by on-line preconcentration of the metal prior to the chromatography using one millilitre injection volumes applied to a calix[4]arene-tetrahydroxamate based chelating precolumn. The method is applied to water samples collected from a river subjected to an industrial effluent discharge and results obtained compare favourably with those obtained using flame atomic absorption spectroscopy.

ISSN:0003-2719    

DOI:10.1080/00032719908542607

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor