Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations

Wu, Nan; Clausen, Ashley

doi:10.1002/jssc.200700026

Cited by 161 publications

(122 citation statements)

References 84 publications

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“…No references were found in the literature regarding their applications for the separation of aloins. Several applications have been developed for chromatographic separation using monolithic columns (see [12] for a review) and UPLC systems (see [13] for a review).…”

Section: Introductionmentioning

confidence: 99%

Improved Chromatographic Methods for Determination of Bioactive Compounds from Aloe vera Leaves

Azaroual

Liazid

Barbero

et al. 2012

ISRN Chromatography

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In this work three chromatographic methods were developed to reduce the total time of the analysis of main compounds in Aloe vera extracts. The first method was developed in a regular reverse phase chromatographic system using a particulate reverse phase C-18 column. Methods already published were used as a starting point for the development of the new method. All the compounds were separated in 32 minutes. The second method was developed in a regular reverse phase chromatographic system employing a monolithic type column. Using a 4.5 mL min −1 flow, the total time of analysis was reduced to 6 minutes with very similar resolution values. The third method was developed in an ultraperformance liquid chromatographic system, and the final time for the analysis of the phenolic compounds was reduced to 4 minutes. The analytical properties of the three chromatographic methods were compared for the main compounds in the chromatograms. Robustness of the three new methods was also checked with regard to the injection volume and the amount of methanol in the sample. A fast method (4 min) is then available for bioactive compounds from Aloe vera determination.

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Section: Introductionmentioning

confidence: 99%

Improved Chromatographic Methods for Determination of Bioactive Compounds from Aloe vera Leaves

Azaroual

Liazid

Barbero

et al. 2012

ISRN Chromatography

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“…11,12 Existem várias alternativas para aumentar a eficiência de uma separação, como usar colunas com maior comprimento, resultando em maiores tempos de análise, ou usar colunas de mesmo comprimento recheadas com partículas de menor diâmetro, resultando em maiores pressões. [13][14][15] No caso de solutos básicos, o uso de fases estacionárias especialmente designadas para tal fim pode aumentar a eficiência e a seletividade da separação, sem qualquer aumento no tempo de análise ou na pressão gerada pelo sistema cromatográfico. Por sua vez, em RP-LC a seletividade de solutos básicos pode ser alterada variando-se parâmetros cromatográficos como o pH da fase móvel, o tipo de tampão, a concentração de tampão e a fase estacionária utilizada.…”

Section: Introductionunclassified

O desafio de analisar solutos básicos por cromatografia líquida em modo reverso: algumas alternativas para melhorar as separações

Borges¹,

Goraieb²

2012

Quím. Nova

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. This review considers some of the difficulties encountered with the analysis of basic solutes using reversed-phase chromatography, such as detrimental interaction with stationary phase silanol groups. Methods of overcoming these problems in reversed-phase separations, by judicious selection of the stationary phase and mobile phase conditions, are discussed. Developments to improve the chemical and thermal stability of stationary phases are also reviewed. It is shown that substantial progress has been made in the manufacturing of stationary phases, enabling their use over a wide variety of experimental conditions. In addition, general measures to significantly extend their lifespan are discussed.Keywords: reversed-phase stationary phases; column classification; chemical and thermal stability. INTRODUÇÃOA cromatografia líquida (LC, liquid chromatography) tem ampla aceitação como técnica analítica, sendo utilizada em muitas áreas da ciência. O modo mais usado desta técnica é o modo reverso (RP-LC, reversed phase liquid chromatography) devido às suas inúmeras vantagens, tais como uso de fases móveis de menor custo e menor toxicidade; rápido equilíbrio da coluna após a mudança de fase mó-vel; possibilidade da condução de separações no modo de eluição por gradiente, resultando em maior rapidez e melhor separação nas análises; boa repetibilidade dos tempos de retenção; amplo campo de aplicação, devido à possibilidade de separação de compostos de diferentes polaridades, massas molares e funcionalidades, dentre outras. 1,2 Por sua vez, mais de 70% dos fármacos disponíveis no mercado são bases e a RP-LC é a técnica mais utilizada para analisar solutos básicos, 1,3 mas alguns problemas acontecem quando solutos básicos são analisados por RP-LC e, por esta razão, esta revisão se dedica a apresentar estes problemas e a fornecer algumas alternativas para superá-los, contribuindo com outras revisões produzidas pelo nosso grupo de pesquisa a respeito da RP-LC. [4][5][6][7][8][9] Em RP-LC o principal objetivo é obter separação dos solutos, que é avaliada através da resolução (R s ), que determinada o grau de separação entre dois picos adjacentes. A resolução pode ser expressa em função da eficiência (N 2 ), da seletividade (α) e do fator de retenção do segundo pico (k 2 ), com a aproximação de que ambos os picos têm aproximadamente a mesma largura à meia altura. De acordo com a equação o aumento do fator de retenção resulta em melhores resoluções apenas quando os solutos forem pouco retidos (fatores de retenção menores que 1) e fatores de retenção maiores que 10 aproximam o termo da equação (k/k+1) à unidade. Enquanto dobrar a eficiência da separação resulta em um aumento da resolução de √ -2 (41%), um aumento na seletividade de 1,05 para 1,10 faz com que a resolução aumente em duas vezes. Desta forma existem duas maneiras de se aumentar a resolução: aumentar a eficiência e aumentar a seletividade da separação. 10 É interessante ressaltar que, ao longo deste texto, serão discutidas alternativas para se alterar a retenção dos so...

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“…The residual phenol content in the dried samples was evaluated by reverse phase (RP) ultra performance liquid chromatography (UPLC) (12). The advantages of the UPLC methods are high resolution, high sensitivity and a high level of robustness, including reproducibility and accuracy (13). While these advantages in general make it a good analytical method both in research and in production of pharmaceutical products, several drawbacks are also present when utilising chromatographic methods.…”

Section: Introductionmentioning

confidence: 99%

Multivariate Analysis of Phenol in Freeze-Dried and Spray-Dried Insulin Formulations by NIR and FTIR

et al. 2011

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Dehydration is a commonly used method to stabilise protein formulations. Upon dehydration, there is a significant risk the composition of the formulation will change especially if the protein formulation contains volatile compounds. Phenol is often used as excipient in insulin formulations, stabilising the insulin hexamer by changing the secondary structure. We have previously shown that it is possible to maintain this structural change after drying. The aim of this study was to evaluate the residual phenol content in spray-dried and freeze-dried insulin formulations by Fourier transform infrared (FTIR) spectroscopy and near infrared (NIR) spectroscopy using multivariate data analysis. A principal component analysis (PCA) and partial least squares (PLS) projections were used to analyse spectral data. After drying, there was a difference between the two drying methods in the phenol/insulin ratio and the water content of the dried samples. The spray-dried samples contained more water and less phenol compared with the freeze-dried samples. For the FTIR spectra, the best model used one PLS component to describe the phenol/insulin ratio in the powders, and was based on the second derivative pre-treated spectra in the 850-650 cm −1 region. The best PLS model based on the NIR spectra utilised three PLS components to describe the phenol/insulin ratio and was based on the standard normal variate transformed spectra in the 6,200-5,800 cm −1 region. The root mean square error of cross validation was 0.69% and 0.60% (w/w) for the models based on the FTIR and NIR spectra, respectively. In general, both methods were suitable for phenol quantification in dried phenol/insulin samples.

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Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations

Cited by 161 publications

References 84 publications

Improved Chromatographic Methods for Determination of Bioactive Compounds from Aloe vera Leaves

Improved Chromatographic Methods for Determination of Bioactive Compounds from Aloe vera Leaves

O desafio de analisar solutos básicos por cromatografia líquida em modo reverso: algumas alternativas para melhorar as separações

Multivariate Analysis of Phenol in Freeze-Dried and Spray-Dried Insulin Formulations by NIR and FTIR

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