Identification of unknown pure component spectra by indirect hard modeling

Kriesten, Ernesto; Mayer, Dieter; Alsmeyer, Frank; Minnich, Clemens B.; Greiner, Lasse; Marquardt, Wolfgang

doi:10.1016/j.chemolab.2008.05.002

Cited by 77 publications

(69 citation statements)

References 24 publications

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“…In order to resolve these ambiguities, the spectra were further analyzed using the indirect hard modelling method (IHM) to obtain further information on the polymorphic content during the crystallization process. The IHM method was proved useful for the analysis of mixture constituents in cases of strongly overlapping spectral bands and nonlinear effects (16,17). Hence, in-line Raman spectra of entacapone crystallization were approximated by the linear combination of pure component models using the IHM approach.…”

Section: In-line Crystallization Monitoringmentioning

confidence: 99%

See 1 more Smart Citation

Fast real-time monitoring of entacapone crystallization and characterization of polymorphs via Raman spectroscopy, statistics and SWAXS

Jednačak¹,

Hodžić²,

Scheibelhofer³

et al. 2014

Acta Pharmaceutica

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Many active pharmaceutical ingredients (APIs) are small organic molecules that have different polymorphic forms (1). It is well known that the API's polymorphic form can affect its physico-chemical properties, such as density, melting point, solubility, stability, morphology and bioavailability (2). Thus, polymorphic screening is a critical part of preformulation studies. The search for possible polymorphic forms typically begins with crystallization of a drug substance from various solvents, including those frequently used during the final crystallization steps (3, 4). Since the API's physicochemical properties can have a dramatic impact on its therapeutic effect, it is crucial to detect the polymorphic form with the characteristics appropriate for the intended use. For this purpose, the parameters affecting the crystallization process should be controlled and optimized (5). Major limitations to improving the control of crystallization parameters Crystallization of the drug entacapone from binary solvent mixtures was monitored in situ using a Raman optical probe. The recorded Raman spectra and statistical analysis, which included the principal components method and indirect hard modeling made it possible to estimate the starting point of crystallization, to assess crystallization temperatures and to provide information on the polymorphic content of the mixture. It was established that crystallization temperatures were proportional to the volume content of the solvent in mixtures. The samples were also evaluated off-line via Raman spectroscopy and SWAXS. The collected data showed the presence of forms b and g in all solvent mixtures. In a toluene/methanol 30:70 mixture, in addition to forms b and g, at least one of the forms A, D or a was also indicated by SWAXS. The results have shown that the presence of a particular polymorph is strongly dependent on the nature and portion of the solvent in the binary solvent mixture.

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Section: In-line Crystallization Monitoringmentioning

confidence: 99%

“…Thus, the analysis of in-line Raman spectra obtained during the crystallization process could reveal polymorphic transformations as a function of time. Quantitative crystallization monitoring by in-line Raman spectroscopy usually involves the design of calibration models derived from the Raman spectra of pure solid-state forms (13)(14)(15)(16)(17).…”

mentioning

confidence: 99%

Fast real-time monitoring of entacapone crystallization and characterization of polymorphs via Raman spectroscopy, statistics and SWAXS

Jednačak¹,

Hodžić²,

Scheibelhofer³

et al. 2014

Acta Pharmaceutica

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show abstract

“…Also in the soft method several constraints, e.g. non-negativity, uni-modality and closure could be applied [20][21][22][23][24][25] . In the present work the formation constants of several bivalent metal ions Cu (II), Ni(II), Co(II), Zn(II) with a new ligand, phenanthrenequinone thiosemicarbazone, were estimated using a model based analysis method.…”

Section: Methodsmentioning

confidence: 99%

Model based multi-wavelength spectrophotometric method for calculation of formation constants of phenanthrenequinone thiosemicarbazone complexes with some metallic cations

Samadi¹,

Salamati²,

Naseri³

2013

10.5267/j.ccl

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In traditional spectrophotometric determination of stability constants of complexation, it is necessary to find a wavelength at which only one of the components has absorbance without any spectroscopic interference of the other reaction components. In the present work, a simple multi-wavelength model-based method has been developed to determine stability constants for complexation reaction regardless of the spectra overlapping of components. Also, pure spectra and concentration profiles of all components are extracted using multi-wavelength model based method. In the present work spectrophotometric titration of several cationic metal ions with new synthetic ligand were studied in order to calculate the formation constant(s). In order to estimate the formation constants a chemometrics method, model based analysis was applied.

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“…However, incorporating a polynomial higher than second order into the global optimization degrades the result of IHM. Although it is claimed that the Lorentzian bands with their extended wings have a high correlation with the polynomial baseline, 11 the method requires extra manual work.…”

Section: Introductionmentioning

confidence: 99%

“…[11][12][13] It utilizes the shapes of individual Raman bands and finally generates physically reasonable spectra for all components. In this method, all the spectra were modeled as a series of parametric functions superimposed on a straight baseline by mathematical optimization.…”

Section: Introductionmentioning

confidence: 99%

Modified Indirect Hard Modeling for Non-invasive Raman Measurements Containing Surface Interference

Ruan

Dai

2012

ANAL. SCI.

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Identification of unknown pure component spectra by indirect hard modeling

Cited by 77 publications

References 24 publications

Fast real-time monitoring of entacapone crystallization and characterization of polymorphs via Raman spectroscopy, statistics and SWAXS

Fast real-time monitoring of entacapone crystallization and characterization of polymorphs via Raman spectroscopy, statistics and SWAXS

Model based multi-wavelength spectrophotometric method for calculation of formation constants of phenanthrenequinone thiosemicarbazone complexes with some metallic cations

Modified Indirect Hard Modeling for Non-invasive Raman Measurements Containing Surface Interference

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