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  1. Article ; Online: Symmetrization of Peaks in Chiral Chromatography with an Area-Invariant Resolution Enhancement Method.

    Handlovic, Troy T / Wahab, M Farooq / Armstrong, Daniel W

    Analytical chemistry

    2022  Volume 94, Issue 48, Page(s) 16638–16646

    Abstract: A majority of enantiomeric separations show some degree of peak asymmetry, which is detrimental to quantitative and semiquantitative chiral analysis. This paper presents a simple and rapid peak symmetrization algorithm for the correction or reduction of ... ...

    Abstract A majority of enantiomeric separations show some degree of peak asymmetry, which is detrimental to quantitative and semiquantitative chiral analysis. This paper presents a simple and rapid peak symmetrization algorithm for the correction or reduction of peak tailing or fronting in exponentially modified Gaussians. Raw chromatographic data can be symmetrized by adding a correct fraction of the first derivative to the chromatogram. The area remains invariant since the area under the first derivative is zero for a pure Gaussian and numerically close to zero for asymmetric peaks. A method of easily extracting the distortion parameter is provided, as well as insight into how pre-smoothing the data with the "perfect smoother" algorithm can suppress high frequencies effectively. The central difference method is also used to compute the first derivative, reducing root-mean-square noise by up to 28% compared to the standard forward difference method. A survey of 40 chiral separations is presented, demonstrating the range of asymmetry observed in chiral separations. Examples of symmetrization of the peaks from enantiomers in comparable and disproportionate concentrations are also provided. Artifacts of deconvolution are discussed, along with methods to mitigate such artifacts.
    Language English
    Publishing date 2022-11-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1508-8
    ISSN 1520-6882 ; 0003-2700
    ISSN (online) 1520-6882
    ISSN 0003-2700
    DOI 10.1021/acs.analchem.2c02683
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.A 4033: Show issues Location:
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  2. Article ; Online: Automated Regularized Deconvolution for Eliminating Extra-Column Effects in Fast High-Efficiency Separations

    Handlovic, Troy T. / Wahab, M. Farooq / Roy, Souvik / Brown, Ronald E. / Armstrong, Daniel W.

    Analytical Chemistry. 2023 July 10, v. 95, no. 29 p.11028-11036

    2023  

    Abstract: With the introduction of ultrahigh efficiency columns and fast separations, the need to eliminate peak deformation contributed by the instrument must be effectively solved. Herein, we develop a robust framework to automate deconvolution and minimize its ... ...

    Abstract With the introduction of ultrahigh efficiency columns and fast separations, the need to eliminate peak deformation contributed by the instrument must be effectively solved. Herein, we develop a robust framework to automate deconvolution and minimize its artifacts, such as negative dips, wild noise oscillations, and ringing, by combining regularized deconvolution and Perona–Malik (PM) anisotropic diffusion methods. A asymmetric generalized normal (AGN) function is proposed to model the instrumental response for the first time. With no-column data at various flow rates, the interior point optimization algorithm extracts the parameters describing instrumental distortion. The column-only chromatogram was reconstructed using the Tikhonov regularization technique with minimal instrumental distortion. For illustration, four different chromatography systems are used in fast chiral and achiral separations with 2.1 and 4.6 mm i.d. columns. Ordinary HPLC data can approach highly optimized UHPLC data. Similarly, in fast HPLC-circular dichroism (CD) detection, 8000 plates were gained for a fast chiral separation. Moment analysis of deconvolved peaks confirms correction of the center of mass, variance, skew, and kurtosis. This approach can be easily integrated and used with virtually any separation and detection system to provide enhanced analytical data.
    Keywords algorithms ; analytical chemistry ; anisotropy ; automation ; chromatography ; deformation ; variance
    Language English
    Dates of publication 2023-0710
    Size p. 11028-11036.
    Publishing place American Chemical Society
    Document type Article ; Online
    ZDB-ID 1508-8
    ISSN 1520-6882 ; 0003-2700
    ISSN (online) 1520-6882
    ISSN 0003-2700
    DOI 10.1021/acs.analchem.3c01279
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

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  3. Article ; Online: Enhancing enantiomeric and diastereomeric separations: A single chromatograph approach for two-dimensional heart-cut methodology.

    J, Siddharth Jaya Sajeevan / Handlovic, Troy T / Wahab, M Farooq / Armstrong, Daniel W

    Talanta

    2023  Volume 267, Page(s) 125243

    Abstract: A high-performance chromatograph was adapted and reconfigured to establish a two-dimensional methodology for separations that are not easily achievable using a single enantioselective column. Allethrin, a pyrethroid used widely as a pesticide in domestic ...

    Abstract A high-performance chromatograph was adapted and reconfigured to establish a two-dimensional methodology for separations that are not easily achievable using a single enantioselective column. Allethrin, a pyrethroid used widely as a pesticide in domestic environments, was chosen as the model analyte. With three chiral centers, it has eight stereoisomers and is considered one of the more difficult chiral separations. Diastereomeric separation was achieved in the first dimension using a shape-selective stationary phase based on ultrapure porous graphitic carbon (particle diameter, 3 μm) in the reversed phase mode. Advanced asymmetric bidirectional peak functions (half-Gaussian modified Gaussian and exponentially modified Gaussian) were employed to extract overlapping peak areas. The four diastereomeric peaks were heart-cut and sent to the second dimension online using a standard six-port 2-position rotary valve. Enantiomeric separation was attained in the second dimension using an immobilized-cellulose tris(3,5-dichlorophenylcarbamate) column (3 μm) with chromatographic resolutions >2.7 for all enantiomeric pairs. The second dimension method was developed using the information from circular dichroism detection. The baseline separation of seven peaks of allethrin in a single dimension was also demonstrated using (2-hydroxypropyl)-β-cyclodextrin. The enantiomeric purity of a purified formulation of allethrin in a commercial pesticide was validated using the developed 2D approach.
    Language English
    Publishing date 2023-09-23
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 1500969-5
    ISSN 1873-3573 ; 0039-9140
    ISSN (online) 1873-3573
    ISSN 0039-9140
    DOI 10.1016/j.talanta.2023.125243
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Automated Regularized Deconvolution for Eliminating Extra-Column Effects in Fast High-Efficiency Separations.

    Handlovic, Troy T / Wahab, M Farooq / Roy, Souvik / Brown, Ronald E / Armstrong, Daniel W

    Analytical chemistry

    2023  Volume 95, Issue 29, Page(s) 11028–11036

    Abstract: With the introduction of ultrahigh efficiency columns and fast separations, the need to eliminate peak deformation contributed by the instrument must be effectively solved. Herein, we develop a robust framework to automate deconvolution and minimize its ... ...

    Abstract With the introduction of ultrahigh efficiency columns and fast separations, the need to eliminate peak deformation contributed by the instrument must be effectively solved. Herein, we develop a robust framework to automate deconvolution and minimize its artifacts, such as negative dips, wild noise oscillations, and ringing, by combining regularized deconvolution and Perona-Malik (PM) anisotropic diffusion methods. A asymmetric generalized normal (AGN) function is proposed to model the instrumental response for the first time. With no-column data at various flow rates, the interior point optimization algorithm extracts the parameters describing instrumental distortion. The column-only chromatogram was reconstructed using the Tikhonov regularization technique with minimal instrumental distortion. For illustration, four different chromatography systems are used in fast chiral and achiral separations with 2.1 and 4.6 mm i.d. columns. Ordinary HPLC data can approach highly optimized UHPLC data. Similarly, in fast HPLC-circular dichroism (CD) detection, 8000 plates were gained for a fast chiral separation. Moment analysis of deconvolved peaks confirms correction of the center of mass, variance, skew, and kurtosis. This approach can be easily integrated and used with virtually any separation and detection system to provide enhanced analytical data.
    Language English
    Publishing date 2023-07-10
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1508-8
    ISSN 1520-6882 ; 0003-2700
    ISSN (online) 1520-6882
    ISSN 0003-2700
    DOI 10.1021/acs.analchem.3c01279
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Cologne/Königswinter

    Zs.A 4033: Show issues Location:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
    Jg. 1995 - 2021: Lesesall (2.OG)
    ab Jg. 2022: Lesesaal (EG)

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  5. Article ; Online: Insights into enantioselective separations of ionic metal complexes by sub/supercritical fluid chromatography

    Handlovic, Troy T. / Wahab, M. Farooq / Cole, Houston D. / Alatrash, Nagham / Ramasamy, Elamparuthi / MacDonnell, Frederick M. / McFarland, Sherri A. / Armstrong, Daniel W.

    Analytica Chimica Acta. 2022 Oct., v. 1228 p.340156-

    2022  

    Abstract: Sub/supercritical fluid chromatography (SFC) is a green separation technique that has been used to separate a wide variety of compounds and is proven to be immensely useful for chiral separations. However, SFC is currently not thought to be applicable ... ...

    Abstract Sub/supercritical fluid chromatography (SFC) is a green separation technique that has been used to separate a wide variety of compounds and is proven to be immensely useful for chiral separations. However, SFC is currently not thought to be applicable for ionic compounds due to their low solubility in CO₂, even with additives and organic modifiers. Recently, a large amount of research has been centered on octahedral complexes of Ru(II) and Os(II) with bidentate polypyridyl ligands due to their ability to serve in cancer treatment and other biological activities. These compounds exist as the delta (Δ) and lambda (Λ) enantiomers. Previously, similar compounds have been enantiomerically separated using HPLC and capillary electrophoresis, but never with SFC. Cyclofructan-6 (CF6) derivatized with (R)-naphthyl ethyl (RN) groups has been proven to be an effective chiral stationary phase for these separations in HPLC. This column chemistry was expanded to SFC to provide the first chiral separation of a wide variety (23 complexes in total) of ionic octahedral polypyridyl complexes. Unexpected behavior for mixing methanol and acetonitrile as the organic modifier will be discussed, along with the effects of additives. Enantioselectivity on CF6-RN chemistry is shown to be dependent on the conjugation level and rigidity of the metal complexes. Mass transfer kinetic behavior is also shown, and high-efficiency baseline resolved rapid separations are shown for fast screening or quantitation of representative coordination complexes.
    Keywords acetonitrile ; cancer therapy ; capillary electrophoresis ; carbon dioxide ; enantiomers ; enantioselectivity ; ligands ; mass transfer ; methanol ; solubility ; supercritical fluid chromatography ; Metal complexes ; Coordination complexes ; Sub/supercritical fluid chromatography ; Cyclofructan derivatives ; Superficially porous particles ; Fast chiral separation
    Language English
    Dates of publication 2022-10
    Publishing place Elsevier B.V.
    Document type Article ; Online
    ZDB-ID 1483436-4
    ISSN 1873-4324 ; 0003-2670
    ISSN (online) 1873-4324
    ISSN 0003-2670
    DOI 10.1016/j.aca.2022.340156
    Database NAL-Catalogue (AGRICOLA)

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  6. Article ; Online: Insights into enantioselective separations of ionic metal complexes by sub/supercritical fluid chromatography.

    Handlovic, Troy T / Wahab, M Farooq / Cole, Houston D / Alatrash, Nagham / Ramasamy, Elamparuthi / MacDonnell, Frederick M / McFarland, Sherri A / Armstrong, Daniel W

    Analytica chimica acta

    2022  Volume 1228, Page(s) 340156

    Abstract: Sub/supercritical fluid chromatography (SFC) is a green separation technique that has been used to separate a wide variety of compounds and is proven to be immensely useful for chiral separations. However, SFC is currently not thought to be applicable ... ...

    Abstract Sub/supercritical fluid chromatography (SFC) is a green separation technique that has been used to separate a wide variety of compounds and is proven to be immensely useful for chiral separations. However, SFC is currently not thought to be applicable for ionic compounds due to their low solubility in CO
    MeSH term(s) Acetonitriles ; Carbon Dioxide ; Chromatography, Supercritical Fluid/methods ; Coordination Complexes ; Ions ; Methanol ; Stereoisomerism
    Chemical Substances Acetonitriles ; Coordination Complexes ; Ions ; Carbon Dioxide (142M471B3J) ; Methanol (Y4S76JWI15)
    Language English
    Publishing date 2022-07-18
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 1483436-4
    ISSN 1873-4324 ; 0003-2670
    ISSN (online) 1873-4324
    ISSN 0003-2670
    DOI 10.1016/j.aca.2022.340156
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    Kategorien

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