Self-immobilization of poly(methyltetradecylsiloxane) onto metalized silica particles as stationary phases for HPLC

This work presents a study of the sorption of a pre-synthesized polysiloxane, poly(methyltetradecylsiloxane) - PMTDS, onto zirconized and titanized-silica particles that results in efficient stationary phases for reversed phase liquid chromatography. The sorbed materials, after 6 days at room temperature without any chemical or physical agent, denominated as self-immobilized stationary phase, present appropriate polymeric layer thicknesses that cover the metalized silica surfaces. The self-immobilization of polymer onto titanized silica particles produces more homogeneous polymeric coatings and stationary phases without silanophilic activity. Zirconized silica-based phases were more chemically resistant, despite their strong retention of basic solutes. In general, the chromatographic performance and chemical stability of metalized silica-based self-immobilized PMTDS phases were similar to conventional chemically bonded stationary phases27712971304CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPSem informaçãoSem informaçã

State-of-the-art in immobilized polymer stationary phases for high-performance liquid chromatography

Increasing stability and reducing the high activity of residual groups from stationary phases have been the main focuses of research on the preparation of reversed-phase high-performance liquid chromatography (RP-HPLC) phases over the last four decades. New and more efficient strategies for modifying the silica surface as well as the introduction of new chromatographic supports have minimized these effects and have enabled the increasing popularization of RP-HPLC. In this paper, an overview will be given of the state-of-the-art in stationary phases for RP-HPLC based on immobilization of pre-synthesized organic polymers on both silica and metalized-silica supports. Special consideration is given to the development of HPLC stationary phases in Brazil in the past 15 years.O aumento da estabilidade química e a redução da alta atividade de grupos residuais têm sido, nas últimas quatro décadas, os principais focos de pesquisas na preparação de fases estacionárias para cromatografia líquida de alta eficiência na modalidade de fase reversa (CLAE-FR). Novas e eficientes estratégias de modificação da superfície da sílica e a introdução de novos materiais como suportes cromatográficos têm minimizado estas limitações e possibilitado uma crescente popularização da CLAE-FR. Neste trabalho será apresentada uma visão geral do estado da arte de uma das estratégias de preparo de fases estacionárias que vem contornando tais limitações da CLAE-FR; as fases estacionárias baseadas na imobilização de polímeros orgânicos pré-sintetizados sobre partículas de sílica e sílica metalizada (zirconizada e titanizada). Uma consideração especial será dada ao desenvolvimento destas fases estacionárias ocorrido no Brasil nos últimos 15 anos.13851398Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

The search for more pH stable stationary phases for high performance liquid chromatography

High performance liquid chromatographic (HPLC) separations are largely carried out using reversed phase conditions with stationary phases based on silica. A serious problem with these stationary phases is the tendency of silica to dissolve in high pH solutions often needed to separate basic compounds. The literature reports many different ways that have been tried to resolve this problem. This paper reports the results obtained in our laboratory with stationary phases prepared using silica supports having a layer of a metal oxide (zirconia or titania) attached on their surfaces, followed by immobilization of a polysiloxane or by organofunctionalization with a trimethoxyalkylsilane. Stability tests, also developed in our laboratory, indicate that the metal oxide layer increases the HPLC column lifetimes by making the stationary phase less susceptible to dissolution.As separações por cromatografia líquida de alta eficiência (CLAE) são realizadas, na maioria das vezes, em condições de fase reversa empregando fases estacionárias a base de sílica. Um problema sério com estas fases reversas é a tendência da sílica dissolver em soluções de pH elevado, frequentemente necessárias para separar compostos básicos. A literatura reporta várias maneiras diferentes de tentar solucionar este problema. Este artigo relata os resultados obtidos com fases estacionárias desenvolvidas no nosso laboratório, utilizando suportes de sílica, contendo uma camada de um óxido metálico (zircônia ou titânia) ligada à sua superfície, seguido por imobilização de um polissiloxano ou por organofuncionalização com um trimetóxialquilsilano. Testes de estabilidade, também desenvolvidos no nosso laboratório, indicaram que a camada de óxido metálico aumenta o tempo de vida da coluna cromatográfica, por tornar a fase estacionária menos susceptível à dissolução.60461

Determination of polymeric layer thickness on immobilized stationary phases for high-performance liquid chromatography using thermogravimetric analyses

This paper presents a simple and practical thermogravimetric method for determining the layer thickness of immobilized polymer stationary phases used in reversed-phase high-performance liquid chromatography. In this method, the weight loss of different polysiloxanes immobilized onto chromatographic supports, determined over the temperature range 150-650 ºC, demonstrated excellent agreement with the sum of carbon and hydrogen content obtained by elemental analysis. The results presented here suggest that the thermogravimetric procedure is an accurate and precise method to determine the polymeric material content on polymer-coated stationary phases.417420Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

The search for more pH stable stationary phases for high performance liquid chromatography

High performance liquid chromatographic (HPLC) separations are largely carried out using reversed phase conditions with stationary phases based on silica. A serious problem with these stationary phases is the tendency of silica to dissolve in high pH solutions often needed to separate basic compounds. The literature reports many different ways that have been tried to resolve this problem. This paper reports the results obtained in our laboratory with stationary phases prepared using silica supports having a layer of a metal oxide (zirconia or titania) attached on their surfaces, followed by immobilization of a polysiloxane or by organofunctionalization with a trimethoxyalkylsilane. Stability tests, also developed in our laboratory, indicate that the metal oxide layer increases the HPLC column lifetimes by making the stationary phase less susceptible to dissolution

Self-Immobilization of Poly(methyltetradecylsiloxane) onto Metalized Silica Particles as Stationary Phases for HPLC

This work presents a study of the sorption of a pre-synthesized polysiloxane, poly(methyltetradecylsiloxane) - PMTDS, onto zirconized and titanized-silica particles that results in efficient stationary phases for reversed phase liquid chromatography. The sorbed materials, after 6 days at room temperature without any chemical or physical agent, denominated as self-immobilized stationary phase, present appropriate polymeric layer thicknesses that cover the metalized silica surfaces. The self-immobilization of polymer onto titanized silica particles produces more homogeneous polymeric coatings and stationary phases without silanophilic activity. Zirconized silica-based phases were more chemically resistant, despite their strong retention of basic solutes. In general, the chromatographic performance and chemical stability of metalized silica-based self-immobilized PMTDS phases were similar to conventional chemically bonded stationary phases

MÉTODO DE PRÉ-CONCENTRAÇÃO E DETERMINAÇÃO DE 17ß- ESTRADIOL: TESTE DE NOVO SORVENTE

Os métodos de monitoramento ambiental para contaminantes emergentes requerem etapa de preparação das amostras para isolar os analitos de interesse. Para tal, a técnica de extração em fase sólida (SPE) é a mais utilizada em conjunto com determinações por técnicas cromatográficas. Este trabalho descreve o desenvolvimento de um método analítico para a determinação da presença e medição das concentrações de um contaminante emergente de ampla ocorrência, o estrogênio 17β-estradiol. Nesta investigação foi testado o uso de um novo sorvente, de hidrofobicidade reduzida, produzido pela imobilização térmica do poli(dimetilsiloxano-co-alquilmetilsiloxano) sobre partículas de sílica, Si(PDAS), resultando uma menor hidrofobicidade. Com a metodologia desenvolvida usando o novo sorvente obteve-se recuperações satisfatórias (108±16%), comprovando sua equivalência frente aos sorventes comerciais utilizando um único solvente de baixo custo (metanol) na eluição

New Stationary Phases For High-performance Liquid Chromatography Based On Poly(methyltetradecylsiloxane) Thermally Immobilized Onto Zirconized Silica.

The modification of silica with zirconium oxide followed by sorption and thermal immobilization of poly(methyltetradecylsiloxane) (PMTDS) is used to prepare a reversed stationary phase for high-performance liquid chromatography. The thermal immobilization of PMTDS on zirconized silica was optimized using a central composite design. The new stationary phase was characterized by spectroscopic and chromatographic methods. Stationary phases with good reproducibility and good chromatographic performance for various compounds were obtained. PMTDS thermally immobilized on zirconized silica presented quite significant chemical stability at pH 10 and 50 degrees C.1122114-2

Development of a Methodology for the Determination of Pesticide Residues in Cajá-Manga Pulp (Spondias dulcis L.) Using Solid-Liquid Extraction with Low-Temperature Partitioning

Emergent fruits with functional properties and sui generis flavours are increasingly gaining international market, mainly due to the pleasant taste and its nutritional properties. However, methodologies for determination of pesticide residues in these fruits are still incipient or nonexistent. In this work, a simple, rapid, and accessible methodology to small laboratories was developed, optimized, and validated for the determination of four pesticide residues in the cajá-manga pulp: chlorpyrifos, thiabendazole, carboxin, and difenoconazole. The extraction of pesticides from the cajá-manga pulp was performed by the liquid-solid extraction with low-temperature partitioning, achieving efficiency in the range of 75.3–129.3% with limits of quantification between 170 and 430 ng·g−1 for all compounds. The methodology was validated according to the SANTE/11813/2017 document, demonstrating good detectability, selectivity, precision, and accuracy with limits of quantification within the range of the maximum residual limits preconized for the compounds. The quantification was performed by gas chromatography with flame ionization detection which, although it does not present the best detectability for the compounds, is a lower cost instrumentation and is available in several analysis laboratories in Brazil, making the method more accessible to evaluate the pesticide residues in fruit pulp. Thus, in this work, a methodology for the determination of pesticides in the cajá-manga pulp is available for the monitoring of pesticide residues in fruit pulp, in an efficient and accessible way