Chemical imaging of small molecules from simple to complex matrices: Quantitative approches based on Surface Enhanced Raman scattering

Conference (2013, July)

Surface Enhanced Raman scattering (SERS) allows to dramatically exalt the Raman diffusion of molecules absorbed or very closed to rough metallic surfaces while keeping their structural information. SERS ... [more ▼]

Surface Enhanced Raman scattering (SERS) allows to dramatically exalt the Raman diffusion of molecules absorbed or very closed to rough metallic surfaces while keeping their structural information. SERS chemical imaging, presenting a high specificity and sensibility, allows acquiring a visual representation of samples combining spectral and spatial measurements. This technique could become a powerful tool in pharmaceutical and biological analysis enabling to identify and quantify molecules thanks to chemometric evaluation while looking at their distribution or their interactions. In this context, SERS chemical imaging is investigated in detection or quantitative determination of molecules in pharmaceutical and biological matrices. The feasibility of making quantitative measurements using SERS is evaluated on small target molecules models such as 4-aminophenol and lactate. Firstly, a SERS method to quantify 4-aminophenol which is the primary impurity of acetaminophen coming from its degradation during the storage or from its synthesis was developed on a real pharmaceutical formulation. The standard addition method was selected as calibration method in order to take into account the matrix effect coming from the different components of the latter. Despite the well-known stability and repeatability problems of SERS, the method was thoroughly validated by means of accuracy profiles as decision tool. Moreover, this validation methodology allowed to define a first estimation of the real analytical performance of the technique. Secondly, the detection of lactate, which is a critical metabolite implicated in several metabolic disorders, was successfully tested in the physiological concentration in a simple matrix. Preliminary results for the determination of this metabolic biomarker were also very promising allowing to consider more complex matrices. Based on these results, SERS chemical imaging was implemented to detect 4-aminophenol in a pharmaceutical tablet formerly pulverised by a SERS substrate. Through this imaging technique, it was not only possible to detect the presence of the impurity at the limit of specification of 0.1% (w/w) but it was also possible to differentiate tablets comprising different concentrations of the latter. These promising results represent the first step towards quantitative measurements using SERS chemical imaging. [less ▲]

Development of quantitative approaches based on Surface Enhanced Raman Scattering chemical imaging

Poster (2013, April 18)

Chromatography in the detection and characterisation of illegal pharmaceutical preparations

in Journal of Chromatographic Science (2013)

Counterfeit and illegal pharmaceutical products are an increasing worldwide problem and constitute a major challenge for analytical laboratories to detect and characterize them. Spectroscopic techniques ... [more ▼]

Counterfeit and illegal pharmaceutical products are an increasing worldwide problem and constitute a major challenge for analytical laboratories to detect and characterize them. Spectroscopic techniques as infrared spectroscopy and Raman spectroscopy were always the first methods of choice to detect counterfeits and illegal preparations, but due to the evolution in the products seized and the necessity of risk assessment, chromatographic methods are becoming more important in this domain. This review intends to give a general overview of the techniques described in literature to characterize counterfeit and illegal pharmaceutical preparations, focussing on the role of chromatographic techniques, with different detection tools. [less ▲]

Intérêt de la microscopie vibrationnelle dans la recherche de nouvelles formulations pharma-ceutiques à haute valeur ajoutée.

Report (2012)

La grande majorité des nouvelles molécules actives présente une faible biodisponibilité dans des formulations pharmaceutiques simples contenant principalement un ou plusieurs constituants et l’actif ... [more ▼]

La grande majorité des nouvelles molécules actives présente une faible biodisponibilité dans des formulations pharmaceutiques simples contenant principalement un ou plusieurs constituants et l’actif faiblement soluble dans l’eau. Dès lors, il est primordial d’investir dans la recherche de nouvelles formulations « plus sophistiquées » (formulations de demain) favorisant la solubilité de l’actif. Cependant cette recherche est limitée par celle de nouveaux outils analytiques pointus permettant de les caractériser, d’étudier les interactions au sein des formulations pharmaceutiques, de comprendre les mécanismes liès à leur formation et in fine de contrôler et garantir leur conformité. Par ailleurs, la Technologie Analytique des Procédés (PAT) est un concept développé par l’Administration Américaine des Aliments et des Médicaments (FDA) et soutenu par l’Agence Européenne des Médicaments (EMA). Ce concept qui devient de plus en plus incontournable (au niveau des dossiers d’Autorisation de Mise sur le Marché). La rapidité de mesure et le caractère non destructif de la spectroscopie vibrationnelle dont fait partie la microscopie Raman la rendent particulièrement compatibles avec ce concept. De plus, les techniques vibrationnelles de part l’absence de préparation de l’échantillon et de l’utilisation de solvant organique rencontrent également le concept de Chimie Verte et donc s’incrivent parfaitement dans un contexte de développement durable et respectueux de l’environnement. L’objectif du présent projet est d’explorer les potentialités de la microscopie Raman dans l’étude pointue des matrices complexes afin d’en améliorer les connaissances tant au niveau de leur charactérisation, des intéractions analyte-matrice que des mécanismes liés à leur formation. L’obtention de ces informations nécéssiteront la recherche de nouvelles méthodologies, outils et règles de décision dédicacés aux aspects qualitatifs et plus encore aux aspects quantiftatifs où l’accès à de telles données est très marginal. L’ensemble de cette recherche sera réalisée sur un modèle complexe, une formulation à haute valeur ajoutée issue de l’industrie pharmaceutique. [less ▲]

Chemometrics and chromatographic fingerprints to discriminate and classify counterfeit medicines containing PDE-5 inhibitors.

in Talanta (2012), 100

Chromatographic fingerprints recorded for a set of genuine and counterfeit samples of Viagra® and Cialis® were evaluated for their use in the detection and classification of counterfeit samples of these ... [more ▼]

Chromatographic fingerprints recorded for a set of genuine and counterfeit samples of Viagra® and Cialis® were evaluated for their use in the detection and classification of counterfeit samples of these groups of medicines. Therefore several exploratory chemometric techniques were applied to reveal structures in the data sets as well as differences among the samples. The focus was on the differentiation between genuine and counterfeit samples and on the differences between the samples of the different classes of counterfeits as defined by the Dutch National Institute for Public Health and the Environment (RIVM). In a second part the revealed differences between the samples were modelled to obtain a predictive model for both the differentiation between genuine and counterfeit samples as well as the classification of the counterfeit samples. The exploratory analysis clearly revealed differences in the data for the genuine and the counterfeit samples and with projection pursuit and hierarchical clustering differences among the different groups of counterfeits could be revealed, especially for the Viagra® data set. For both data sets predictive models were obtained with 100% correct classification rates for the differentiation between genuine and counterfeit medicines and high correct classification rates for the classification in the different classes of counterfeit medicines. For both data sets the best performing models were obtained with Least Square-Support Vector Machines (LS-SVM) and Soft Independent Modelling by Class Analogy (SIMCA). [less ▲]

Classification trees based on infrared spectroscopic data to discriminate between genuine and counterfeit medicines

in Journal of Pharmaceutical & Biomedical Analysis (2012), 57(1), 68-75

Classification trees built with the Classification And Regression Tree algorithm were evaluated for modelling infrared spectroscopic data in order to discriminate between genuine and counterfeit drug ... [more ▼]

Classification trees built with the Classification And Regression Tree algorithm were evaluated for modelling infrared spectroscopic data in order to discriminate between genuine and counterfeit drug samples and to classify counterfeit samples in different classes following the RIVM classification system. Models were built for two data sets consisting of the Fourrier Transformed Infrared spectra, the Near Infrared spectra and the Raman spectra for genuine and counterfeit samples of respectively Viagra® and Cialis®. Easy interpretable models were obtained for both models. The models were validated for their descriptive and predictive properties. The predictive properties were evaluated using both cross validation as an external validation set. The obtained models for both data sets showed a 100% correct classification for the discrimination between genuine and counterfeit samples and 83.3% and 100% correct classification for the counterfeit samples for the Viagra® and the Cialis® data set respectively. [less ▲]

Classification trees based on infrared spectroscopic data to discriminate between genuine and counterfeit medecines

Conference (2011, September 23)

Classification trees built with the Classification And Regression Tree algorithm were evaluated for modelling infrared spectroscopic data in order to discriminate between genuine and counterfeit drug ... [more ▼]

Classification trees built with the Classification And Regression Tree algorithm were evaluated for modelling infrared spectroscopic data in order to discriminate between genuine and counterfeit drug samples and to classify counterfeit samples in different classes following the RIVM classification system. Models were built for two data sets consisting of the Fourier Transform Infrared spectra, the Near Infrared spectra and the Raman spectra for genuine and counterfeit samples of respectively Viagra® and Cialis®. Easy interpretable models were obtained for both models. The models were validated for their descriptive and predictive properties. The predictive properties were evaluated using both cross validation as an external validation set. The obtained models for both data sets showed a 100% correct classification for the discrimination between genuine and counterfeit samples and 83.3% and 100% correct classification for the counterfeit samples for the Viagra® and the Cialis® data set respectively. [less ▲]

Impurity fingerprints for the identification of counterfeit medicines - a feasibility study

Poster (2011, June 22)

Detection of counterfeit Viagra by Raman microspectroscopy imaging and multivariate analysis

Conference (2011, May 13)

Development and validation of a ultra-high-performance liquid chromatography-UV method for the detection and quantification of erectile dysfunction drugs and some of their analogues found in counterfeit medicines

in Journal of Chromatography. A (2011), 1218

Pharmaceutical counterfeiting is a permanently growing problem. Control laboratories are constantly analysing counterfeit medicines. In industrialised countries, one of the main counterfeited class of ... [more ▼]

Pharmaceutical counterfeiting is a permanently growing problem. Control laboratories are constantly analysing counterfeit medicines. In industrialised countries, one of the main counterfeited class of medicines are erectile dysfunction drugs. This paper describes the development and validation of a fast method to detect and quantify the three authorised phosphodiesterase type 5 inhibitors and five analogues. The method is based on the use of a sub-2 microns polar-embedded column with a gradient using acetonitrile as organic modifier and 10 mM ammonium formate buffer (pH 3.5) as aqueous component of the mobile phase. The separation was achieved in less than 4.5 min. The method has also been compared to the registered HPLC method for the assay of Viagra® which was considered as the reference method. The method is also compatible with on-line coupling mass spectrometry and will significantly reduce analysis times and solvent consumption. [less ▲]