Výsledky vyhledávání - "Valfredo A. Lemos"

Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Based on Melting of the Donor Phase: a New Approach for the Determination of Trace Elements in Solid Samples

Autor: Jorge S. Almeida, Gabriel L. Santos, Lucilia A. Meira, Ana Carla de Souza Nascimento, Leonardo S. G. Teixeira, Valfredo Azevedo Lemos

Publikováno v: Food Analytical Methods. 14:596-605

A novel ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) based on melting of the donor phase for the determination of Cd, Cu, and Fe in margarine samples using high-resolution continuum source electrothermal atomic absorption s

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::659e808b0e0616569324ac3cf6c3768c
https://doi.org/10.1007/s12161-020-01897-y

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Direct Immersion Single-Drop Microextraction and Continuous-Flow Microextraction for the Determination of Manganese in Tonic Drinks and Seafood Samples

Autor: Valfredo Azevedo Lemos, Maria das Graças Andrade Korn, Leane Santos Nunes

Publikováno v: Food Analytical Methods. 13:1681-1689

Two methods based on direct immersion single-drop microextraction (DI-SDME) and continuous-flow microextraction (CFME) were developed. Both methods were used for the determination of manganese by graphite furnace atomic absorption spectrometry. The r

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::c439a9a00e81c813be56e7e67df3ced6
https://doi.org/10.1007/s12161-020-01794-4

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Emulsification solidified floating organic drop microextraction assisted by ultrasound for the determination of nickel, cobalt and copper in oyster and fish samples

Autor: Fabio de S. Dias, Laís N. Pires, Salvador C. de S. R. Neto, Valfredo Azevedo Lemos

Publikováno v: Analytical Methods. 12:865-871

In the present work, solidified floating organic drop microextraction assisted by ultrasound is proposed as the preconcentration system for the determination of trace amounts of nickel, cobalt and copper by FAAS. The main parameters such as pH, conce

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::5d9581abdaf8421f349b9071831f12de
https://doi.org/10.1039/c9ay02453k

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Akademický článek

Aplicação de um corante tiazolilazo como indicador ácido-base e determinação das suas constantes de ionização ácida Application of a thiazolylazo dye as an acid-base indicator and determination of its acid ionization constants

Autor: Regina Terumi Yamaki, Daniel Rodrigues Vieira, Cleber Galvão Novaes, Hygor Rodrigues de Oliveira, Valfredo Azevedo Lemos, Sandra Carvalho

Publikováno v: Química Nova, Vol 32, Iss 7, Pp 1943-1946 (2009)

The pKa values of the 6-[2´-(6´-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD) have been determined at 25 °C, in 0.10 mol L-1 NaCl medium by spectrophotometric method. The SQUAD computer program was used to process e

Externí odkaz: https://doaj.org/article/9601afffb4b5466cbf0795a32bb3dc5c

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A new method for the speciation of arsenic species in water, seafood and cigarette samples using an eggshell membrane

Autor: Alexilda Oliveira de Souza, Djalma Menezes de Oliveira, Luana Bastos Santos, Valfredo Azevedo Lemos

Publikováno v: Journal of the Iranian Chemical Society. 16:1879-1889

This work is based on the application of the eggshell membrane (ESM) of fresh chicken as a sorbent in a solid phase extraction procedure for arsenic speciation with detection by electrothermal atomic absorption spectrometry. The ESM can adsorb severa

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::fa089aa71953e3daf5a3c2f10a34ddcd
https://doi.org/10.1007/s13738-019-01665-8

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A closed inline system for sample digestion using 70% hydrogen peroxide and UV radiation. Determination of lead in wine employing ETAAS

Autor: Valfredo Azevedo Lemos, Luciana A. Silva, Rosemário Cerqueira Souza, Adriano V.B. Chagas, Sergio Luis Costa Ferreira, Caio S.A. Felix, Raineldes A. Cruz Junior

Publikováno v: Talanta. 191:479-484

This paper proposes a closed inline system for decomposition of wine, aiming at the determination of lead using electrothermal atomization atomic absorption spectrometry (ETAAS). The system is built using a 0.8 mm diameter PTFE tube, which is wrapped

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::73ae72978daaedab5fc708dfdf611c8b
https://doi.org/10.1016/j.talanta.2018.08.085

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Liquid phase microextraction associated with flow injection systems for the spectrometric determination of trace elements

Autor: Walter Nei Lopes dos Santos, Sergio Luis Costa Ferreira, Valfredo Azevedo Lemos, Luana Bastos Santos, Rebeca Moraes Menezes, Rafael Vasconcelos Oliveira

Publikováno v: TrAC Trends in Analytical Chemistry. 110:357-366

Liquid phase microextraction (LPME) has been widely used in extraction and preconcentration systems as an excellent alternative to conventional liquid phase extraction. In this work, a critical review is presented on LPME-based flow injection preconc

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::d969b18b891aa186236fc253e3795e39
https://doi.org/10.1016/j.trac.2018.11.031

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