MAGIC-LC/FT-IR Spectrometry: Preliminary Studies

1988 ◽  
Vol 42 (8) ◽  
pp. 1365-1368 ◽  
Author(s):  
R. M. Robertson ◽  
J. A. De Haseth ◽  
J. D. Kirk ◽  
R. F. Browner
Keyword(s):  
Phase Composition ◽  
Mobile Phase ◽  
Mobile Phase Composition ◽  
Reverse Phase ◽  
Ir Spectrometry ◽  
Aerosol Generation ◽  
Mobile Phases ◽  
Ft Ir ◽  
Effluent Stream ◽  
Phase Water

A new solvent elimination interface based on the Monodisperse Aerosol Generation Interface for Combining Liquid Chromatography with Fourier transform infrared (MAGIC-LC/FT-IR) spectrometry is described. The solvent elimination efficiency of MAGIC-LC/FT-IR was studied by varying the mobile-phase composition from 100% methanol to 100% water. As the mobile-phase composition was varied, erythrosin B was injected into the interface and deposited on a KBr window after the solvent removal. Spectra were obtained which compared favorably with reference spectra, even as the mobile-phase water content was increased. A reverse-phase separation was completed to demonstrate that readily identifiable spectra can be obtained from mobile phases containing high percentages of water, without heating of the effluent stream.

Determination of agrochemical combinations in spiked soil samples

1998 ◽  
Vol 37 (8) ◽  
pp. 243-250 ◽  
Author(s):  
Sandra Babic ◽  
Marija Kastelan-Macan ◽  
Mira Petrovic
Keyword(s):  
Phase Composition ◽  
Mobile Phase ◽  
Soil Samples ◽  
Computer Assisted ◽  
Mobile Phase Composition ◽  
Reverse Phase ◽  
Spiked Soil ◽  
Layer Chromatography ◽  
Slit Scanning

Quantitative determination of combinations of the agrochemicals: atrazine, propham, chlorpropham, diflubenzuron, α-cypermethrin and tetramethrin from spiked soil is reported. Method involves ultrasonic extraction of agrochemicals with acetone, separation of samples by means of reverse-phase thin-layer chromatography and quantification by slit-scanning densitometry. Computer-assisted optimisation was used to select the optimum mobile phase composition. Apparent recoveries of agrochemicals from spiked soil were: 90.3±8.5 for chlorpropham, 79.3±10.3 for propham, 102±2.4 for atrazine, 100.6±5.4 for α-cypermethrin, 103.0±4.1 for tetramethrin and 98.3±4.9 for diflubenzuron.

scholarly journals Retention Behaviour in Micellar Liquid Chromatography

2012 ◽  
Vol 2012 ◽  
pp. 1-5
Author(s):  
Maria Rambla-Alegre
Keyword(s):  
Liquid Chromatography ◽  
Phase Composition ◽  
Mobile Phase ◽  
A Priori ◽  
Great Accuracy ◽  
Micellar Liquid Chromatography ◽  
Computer Assisted ◽  
Mobile Phase Composition ◽  
Mobile Phases ◽  
Sequential Strategy

Retention in micellar liquid chromatography is highly reproducible and can be modelled using empirical or mechanistic models with great accuracy to predict the retention changes when the mobile phase composition varies (surfactant and organic solvent concentrations), thus facilitating the optimisation of separation conditions. In addition, the different equilibria inside the column among the solute, the mobile phase, and the modified stationary phase by monomers of surfactant have been exhaustively studied. In a sequential strategy, the retention of the solutes is not known a priori, and each set of mobile phases is designed by taking into account the retention observed with previous eluents. By contrast, in an interpretative strategy, the experiments are designed before the optimization process and used to fit a model that will allow the prediction of the retention of each solute. This strategy is more efficient and reliable. The sequential strategy will be inadequate when several local and/or secondary maxima exist, as frequently occurs in chromatography, and may not give the best maximum, that is to say, the optimum. More often than not, the complexity of the mixtures of compounds studied and the relevant modification of their chromatographic behaviour when changing the mobile phase composition requires the use of computer-assisted simulations in MLC to follow the modifications in the chromatograms in detail. These simulations can be done with sound reliability thanks to the use of chemometrics tools.

scholarly journals Revising Reverse-Phase Chromatographic Behavior for Efficient Differentiation of Both Positional and Geometrical Isomers of Dicaffeoylquinic Acids

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Keabetswe Masike ◽  
Ian Dubery ◽  
Paul Steenkamp ◽  
Elize Smit ◽  
Edwin Madala
Keyword(s):  
Phase Composition ◽  
Uv Irradiation ◽  
Mobile Phase ◽  
Elution Order ◽  
Elution Profile ◽  
Plant Metabolites ◽  
Mobile Phase Composition ◽  
Reverse Phase ◽  
Geometrical Isomers ◽  
Column Temperature

Dicaffeoylquinic acids (diCQAs) are plant metabolites and undergo trans-cis-isomerization when exposed to UV irradiation. As such, diCQAs exist in both trans- and cis-configurations and amplify the already complex plant metabolome. However, analytical differentiation of these geometrical isomers using mass spectrometry (MS) approaches has proven to be extremely challenging. Exploring the chromatographic space to develop possible conditions that would aid in differentially separating and determining the elution order of these isomers is therefore imperative. In this study, simple chromatographic parameters, such as column chemistry (phenyl versus alkyl), mobile phase composition (methanol or acetonitrile), and column temperature, were investigated to aid in the separation of diCQA geometrical isomers. The high-performance liquid chromatography photodiode array (HPLC-PDA) chromatograms revealed four isomers post UV irradiation of diCQA authentic standards. The elution profile/order was seen to vary on different reverse-phase column chemistries (phenyl versus alkyl) using different mobile phase composition. Here, the elution profile/order on the phenyl-derived column matrices (with methanol as the mobile phase composition) was observed to be relatively reproducible as compared to the alkyl (C18) columns. Chromatographic resolution of diCQA geometrical isomers can be enhanced with an increase in column temperature. Lastly, the study highlights that chromatographic elution order/profile cannot be relied upon to fathom the complexity of isomeric plant metabolites.

MAGIC-LC/FT-IR Spectrometry with Buffered Solvent Systems

1990 ◽  
Vol 44 (1) ◽  
pp. 8-13 ◽  
Author(s):  
R. M. Robertson ◽  
J. A. de Haseth ◽  
R. F. Browner
Keyword(s):  
Mobile Phase ◽  
Potassium Dihydrogen Phosphate ◽  
Dihydrogen Phosphate ◽  
Reference Spectrum ◽  
Ir Spectrometry ◽  
Potassium Dihydrogen ◽  
Aerosol Generator ◽  
Mobile Phases ◽  
Potassium Hydrogen ◽  
Ft Ir

The first demonstration of identifiable infrared (IR) spectra obtained from buffered (volatile and nonvolatile buffers) mobile phases using the Monodisperse Aerosol Generator Interface for Combining Liquid Chromatography with Fourier Transform Infrared (MAGIC-LC/FT-IR) spectrometry is described. Ammonium acetate, a volatile buffer, was used to buffer an 80:20 acetonitrile: water mobile phase to pH 5.0. Caffeine was deposited from this buffered mobile phase, and the spectrum was used as a reference to compare with caffeine spectra obtained from nonvolatile buffered mobile phases. The two nonvolatile buffers used were potassium hydrogen phthalate (KHP) and potassium dihydrogen phosphate (KH2PO4). The KH2PO4 was used to buffer an acetonitrile:water mobile phase and a methanol:water mobile phase, whereas the KHP buffer was used only in a methanoh:water mobile phase. Samples of caffeine were deposited from each of the above buffer systems along with the nonvolatile buffer. Infrared spectra of caffeine were obtained by spectral subtraction of previously stored buffer spectra from the caffeine:buffer spectra. The resulting spectra were identical to a caffeine reference spectrum.

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