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1.
Molecules ; 27(9)2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35566264

RESUMO

A rapid and sensitive technique for frauds determination in vanilla flavors was developed. The method comprises separation by liquid chromatography followed by an electrochemical detection using a homemade screen-printed carbon electrode modified with aluminium-doped zirconia nanoparticles (Al-ZrO2-NPs/SPCE). The prepared nanomaterials (Al-ZrO2-NPs) were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). This method allows for the determination of six phenolic compounds of vanilla flavors, namely, vanillin, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillyl alcohol, vanillic acid and ethyl vanillin in a linear range between 0.5 and 25 µg g-1, with relative standard deviation values from 2.89 to 4.76%. Meanwhile, the limits of detection and quantification were in the range of 0.10 to 0.14 µg g-1 and 0.33 to 0.48 µg g-1, respectively. In addition, the Al-ZrO2-NPs/SPCE method displayed a good reproducibility, high sensitivity, and good selectivity towards the determination of the vanilla phenolic compounds, making it suitable for the determination of vanilla phenolic compounds in vanilla real extracts products.


Assuntos
Nanopartículas , Vanilla , Alumínio , Cromatografia Líquida/métodos , Técnicas Eletroquímicas , Eletrodos , Aromatizantes/análise , Nanopartículas/análise , Fenóis/química , Reprodutibilidade dos Testes , Vanilla/química , Zircônio
2.
Molecules ; 26(9)2021 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-34063259

RESUMO

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO2NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO2) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.


Assuntos
Análise de Alimentos/métodos , Nanotubos de Carbono/química , Polímeros/química , Rodaminas/análise , Adsorção , Técnicas Eletroquímicas , Eletrodos , Concentração de Íons de Hidrogênio , Limite de Detecção , Magnetismo , Microscopia Eletrônica de Varredura , Impressão Molecular , Polímeros Molecularmente Impressos , Poliestirenos/química , Reprodutibilidade dos Testes , Espalhamento de Radiação , Sensibilidade e Especificidade , Extração em Fase Sólida/métodos , Análise Espectral Raman , Titânio/química
3.
Environ Sci Pollut Res Int ; 25(22): 22060-22074, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29802610

RESUMO

The work shown in this article demonstrate a novel example of converting olive industry solid waste (OISW) into a magnetic cellulose nanocrystalline (MNCs) to serve as selective magnetic sorbents for methylene blue. Olive industry solid waste contains about 40% cellulose. The cellulose was extracted in a powder form from olive industry solid waste by subjecting it to a multistep pulping and bleaching process. The extracted powder cellulose was then converted to nanocrystalline cellulose (NCs) by acid hydrolysis. The NCs were then treated with a solution of FeCl3.6H2O, FeSO4, and H2O by a colloidal suspension method which produced free-flowing porous MNCs. The produced MNCs are characterized by several spectroscopic and analytical techniques such as SEM, TEM, XRD, FTIR VSM, and TGA. The efficiency of the three polymers cellulose powder, NCs, and MNCs toward extracting methylene blue (MB) from water was evaluated. Cellulose powder and NCs showed acceptable tendency for methylene blue. However, MNCs showed excellent extraction efficiency toward MB. The thermodynamic studies revealed a spontaneous adsorption of MB by MNCs at various temperatures. The spontaneous adsorption could be attributed to the electrostatic interaction and H-bonding between MNCs and MB. However, the interaction between cellulose, NCs, and MB is limited to the H-bonding.


Assuntos
Celulose/química , Azul de Metileno/isolamento & purificação , Resíduos Sólidos , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Indústria de Processamento de Alimentos , Magnetismo , Azul de Metileno/química , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Nanoestruturas/química , Olea , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Águas Residuárias/química , Poluentes Químicos da Água/química , Difração de Raios X
4.
Talanta ; 166: 63-69, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-28213259

RESUMO

Two methods for the determination of Sudan dyes (Sudan I, Sudan II, Sudan III and Sudan IV) in food samples, by solid phase extraction - capillary liquid chromatography, are proposed. Both methods use nanocellulose (NC) extracted from bleached argan press cake (APC), as a nano-adsorbent recycled from an agricultural waste material. One of the methods involves the dispersion of NC in food sample extracts, along with the waste and eluents being separated by centrifugation. In the other method, NC was modified by magnetic iron nanoparticles before using it in the extraction of Sudan dyes. The use of a magnetic component in the extraction process allows magnetic separation to replace the centrifugation step in a convenient and economical way. The two proposed methods allows the determination of Sudan dye amounts at the 0.25-2.00µgL-1 concentration range. The limit of detections, limit of quantifications and standard deviations achieved were lower than 0.1µgL-1, 0.20µgL-1 and 3.46% respectively, when using NC as a nano-adsorbent, and lower than 0.07µgL-1, 0.23µgL-1 and 2.62%, respectively, with the magnetic nanocellulose (MNC) was used. Both methods were applied to the determination of Sudan dyes in barbeque and ketchup sauce samples, obtaining recoveries between 93.4% and 109.6%.


Assuntos
Celulose/química , Fracionamento Químico/métodos , Corantes/análise , Corantes/isolamento & purificação , Análise de Alimentos/métodos , Imãs/química , Nanoestruturas/química , Cromatografia Líquida , Óleos de Plantas/química
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