Cloud point formation based on mixed micelles in the presence of electrolytes for cobalt extraction and preconcentration

A new micelle-mediated phase separation of metal ions, applied for preconcentrating trace levels of cobalt as a prior step to its determination by flame atomic spectroscopy, has been developed. Two methods were proposed employing both Triton X-100 and sodium dodecyl sulfate (SDS) as a mixed micellar system while the phase separation was induced by HCl or NaCl addition. Cobalt was complexed with pyridylazo compounds (PAN, PAR, 5-Br-PADAP) in an aqueous surfactant medium and it was concentrated in the surfactant rich phase after phase separation. The chemical variables affecting the cloud point extraction were evaluated, optimized and successfully applied to cobalt determination in pharmaceutical samples. Under the optimized conditions, the preconcentration system permitted limits of detection as 1.1 and 1.6 mug l(-1) cobalt, respectively, when HCl and NaCl were used. Both proposed methods showed linear calibration within a 25-200 mug l(-1) cobalt range. The extraction efficiency was investigated at different cobalt concentrations (40-185 mug l(-1)) and good recoveries (98-102%) were obtained by using NaCl as electrolyte. The results obtained were compared with those observed with ET AAS. (C) 2003 Elsevier B.V. All rights reserved.61675976

A fast ultrasound-assisted extraction of Ca, Mg, Mn and Zn from vegetables

A fast and accurate method for the extraction of Ca, Mg, Mn and Zn from vegetables is proposed. Ultrasonic energy and dilute acid are used for the extraction. Optimisation conditions for the ultrasonic bath were established: 1 1 of water; 25 degreesC; 2% v/v detergent concentration; horizontal and vertical positions in the bath for sonicating samples: central and bottom, respectively. Using these conditions, the nitric acid concentration (0-1.4 mol 1(-1)), sonication time (0-30 min) and particle size (150-63 mum) were optimised. The best conditions for extraction were: 0.14 mol 1(-1) HNO3, 10 min of sonication time and a particle size < 75 <mu>m. The accuracy of the proposed ultrasound-assisted extraction method was assessed by using certified reference materials, as well as wet digestion. Recoveries ranging from 96 to 102% were obtained under the extraction conditions mentioned above with different kinds of plant samples for the majority of the metals studied. (C) 2001 Elsevier Science B.V. All rights reserved.691374

Direct determination of Cu and Zn in fruit juices and bovine milk by thermospray flame furnace atomic absorption spectrometry

In the present work, thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was employed for Cu and Zn determination in bovine milk and fruit juice samples without any pretreatment. TS-FF-AAS system was optimized and a sample volume of 300 mul was injected into the carrier stream (0.014 mol I-1 HNO3 at a flow rate of 0.4 ml min(-1)), and it was introduced into a hot Ni tube. The detection limits obtained for Cu and Zn in aqueous solution were 2.2 and 0.91 mug l(-1), respectively, and 3.2 mug l(-1) for Cu in a medium containing water-soluble tertiary amines. The relative standard deviations varied from 2.7 to 4.2% (n = 12). Sample preparation was carried out by simple dilution in water or in water-soluble tertiary amines medium. Accuracy was checked by performing addition-recovery experiments as well as by using reference materials (whole milk powder, non-fat milk powder, and infant formula). Recoveries varied from 97.7 to 105.3% for Cu and Zn. All results obtained for reference materials were in agreement with certified values at a 95% confidence level. (C) 2004 Elsevier B.V. All rights reserved.64491291

Continuous photometric method for the screening of human urines for phenothiazines

A fully automated urinary screening system for five phenothiazines has been developed. The method is based on the oxidation of phenothiazines in acid medium to colourless sulphoxides via orange or purple coloured intermediates, which are continuously monitored at 520 nm. Two innovations have been implemented versus the conventional method; first, sulphuric acid (ideal reaction medium) has been changed by nitric acid (less corrosive, and compatible with pumping tubes) and second, problems associated with the instability of phenothiazonium radical cation are eliminated as the measurements are carried out simultaneously to the formation of the coloured products in the flow system. The configuration adopted permits selective retention of phenothiazines on a LiChrolut(R)-EN sorbent column before their oxidation with hexacyanoferrate(III) ions in acid medium. The proposed method allows phenothiazines determination within the interval 3-50 muM (1-20 mug ml(-1)), with a throughput of 12 h(-1); an average relative S.D. of 4% (n = 11) was obtained for phenothiazine concentration of 5 muM. Finally, a comprehensive study of 50 real urine samples (phenothiazines free) obtained from different individuals provided 6% of false positives and 0% false negatives for chlorpromazine concentrations of 1.5 and 3 muM, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.462227528

LSD and 9,10-dihydro-LSD Analyses in Street Drug Blotter Samples via Easy Ambient Sonic-Spray Ionization MassSpectrometry (EASI-MS)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Normally, the identification of the LSD drug is performed by forensic laboratories, using the Ehrlich spot test. However, this is a nonspecific analysis. Additionally, the Brazilian Federal Police has identified the presence of a new compound in seized blotters: 9,10-dihydro-LSD, an uncontrolled substance. In this work, easy ambient sonic-spray ionization mass spectrometry in the positive ion mode, EASI(+)-MS, was used to characterize LSD and 9,10-dihydro-LSD compositions directly from the surface of blotters. The presence of LSD in the seized blotter samples were also confirmed via high-performance liquid chromatography with ultraviolet detector. In a set of 41 blotters analyzed by EASI(+)-MS, 28 showed positive results for LSD, seven for 9,10-dihydro-LSD, and another six samples showed negative results for both LSD and 9,10-dihydro-LSD. The combination of thin layer chromatography with EASI-MS also demonstrated to be a relatively simple and powerful screening tool for forensic analysis of street drugs.57513071312Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)FINEPFundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2009/07168-9]CNPq [576183/2008-3]FAPERJ [E-26/190.060/2008]FAPEMIG [PRONEX 479/2007