Nicolas Cimetiere

Standard addition method for the determination of pharmaceutical residues in drinking water by SPE–LC–MS/MS

The study of the occurrence and fate of pharmaceutical compounds in drinking or waste water processes has become very popular in recent years. Liquid chromatography with tandem mass spectrometry is a powerful analytical tool often used to determine pharmaceutical residues at trace level in water. However, many steps may disrupt the analytical procedure and bias the results. A list of 27 environmentally relevant molecules, including various therapeutic classes and (cardiovascular, veterinary and human antibiotics, neuroleptics, non-steroidal anti-inflammatory drugs, hormones and other miscellaneous pharmaceutical compounds), was selected. In this work, a method was developed using ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC–MS/MS) and solid-phase extraction to determine the concentration of the 27 targeted pharmaceutical compounds at the nanogram per litre level. The matrix effect was evaluated from water sampled at different treatment stages. Conventional methods with external calibration and internal standard correction were compared with the standard addition method (SAM). An accurate determination of pharmaceutical compounds in drinking water was obtained by the SAM associated with UPLC–MS/MS. The developed method was used to evaluate the occurrence and fate of pharmaceutical compounds in some drinking water treatment plants in the west of France.

Impurity profiling of trandolapril under stress testing: Structure elucidation of by-products and development of degradation pathway.

Various regulatory authorities like International Conference on Harmonization (ICH), US Food and Drug Administration, Canadian Drug and Health Agency are emphasizing on the purity requirements and the identification of impurities in active pharmaceutical drugs. Qualification of the impurities is the process of acquiring and evaluating data that establishes biological safety of an individual impurity; thus, revealing the need and scope of impurity profiling of drugs in pharmaceutical research. As no stability-indicating method is available for identification of degradation products of trandolapril, a new angiotensin converting enzyme inhibitor (ACEI), under stress testing, the development of an accurate method is needed for quantification and qualification of degradation products. Ultra high performance liquid chromatography (UPLC) coupled to electrospray tandem mass spectrometry was used for the rapid and simultaneous analysis of trandolapril and its degradation products. Chromatographic separation was achieved in less than 4 min, with improved peak resolution and sensitivity. Thanks to this method, the kinetics of trandolapril degradation under various operating conditions and the characterization of the structure of the by-products formed during stress testing have been determined. Thereafter, a mechanism of trandolapril degradation in acid and neutral conditions, including all the identified products, was then proposed.

Forced Degradation Study of Quinapril by UPLC-DAD and UPLC/ MS/MS: Identification of By-products and Development of Degradation Kinetics

3 Quinapril undergoes a significant degradation in the solid state, especially in the presence of humidity, 4 temperature and pharmaceutical excipients. Since dissolution increases the degradation, hydrolytic reactions are 5 among the most common processes involved in drug degradation. Improving the knowledge regarding drug 6 stability, especially concerning the critical factors that can influence the stability of the active substance in 7 solutions, such as the temperature, the pH and the concentration of catalytic species usually acids or bases is 8 essential for pharmaceutical use; the aim of this study was therefore to develop a new chromatographic method 9 for rapidly and accurately assess the chemical stability of pharmaceutical dosage in acidic, neutral and alkaline 10 media at 80°C according to the ICH guidelines. Ultra High Performance Liquid Chromatography (UPLC) 11 coupled to electrospray ionization tandem mass spectrometry was used for the rapid and simultaneous analysis of 12 quinapril and its by-products. Separation was achieved using a BEH C18 column and a mixture of acetonitrile 13 ammonium hydrogencarbonate buffer (pH 8.2; 10 mM) (65:35, v/v) with a flow rate of 0.4 mL/min as a mobile 14 phase. This method allowed the drug by-products profiling, identification, structure elucidation and quantitative 15 determination of by-products under stress conditions. The developed method also provides the determination of 16 the kinetic rate constants for the degradation of quinapril and the formation of its major by-products. Kinetic 17 study and the structure elucidation of by-products allow the development of a complete model including 18 degradation pathway observed under all tested conditions. 19

Investigation of the Rotational Isomerism of Quinapril and Quinaprilat by UPLC-DAD and Elucidation of the Conformational Equilibrium by NMR

Quinapril and quinaprilat are two angiotensin-converting enzyme inhibitors (ACEIs) characterized by a peak broadening and splitting when they were analyzed by ultra-performance liquid chromatography (UPLC). This phenomenon is due to the existence of the two isomers cis and trans around the amide band. In order to confirm the existence of the two conformers and allow identification of the predominant form, NMR studies of quinapril, involving 1H, 13C, 1H-1HCOSY, Impact-HMBC, JMOD, HSQC, and ROESY have been conducted in this work. The analyses allowed us to identify the predominant form of quinapril; the conformer trans is the predominant form (75 %). In addition, this study highlights the important benefits of UPLC to separate quinapril and quinaprilat isomers due to its high resolving power. The effect of various operating conditions on the retention peak, namely, splitting and band broadening of quinaprilat and quinapril, has been qualitatively examined in this study. Several practical experimental conditions have been tested, allowing both the elution of the two ACEIs as single peaks, while keeping at the same time an acceptable separation. The effect of various factors on the conformational s-cis–s-trans equilibrium of quinapril and quinaprilat, namely, the composition of the mobile phase, column temperature, flow rate, pH, and type and amount of organic modifier was investigated by UPLC–DAD (diode array detector) with a BEH C18 column (100 mm, 2.1 mm internal diameter × 1.7 µm particle diameter). Several deconvolution models were used to model overlapped peaks and to determine resolution. Results obtained showed that a mobile phase consisting of ammonium buffer (10 mM; pH 8) and acetonitrile allows the separation of the quinapril and quinaprilat conformers. Maximum resolution was obtained for a composition of mobile phase (55/45) and (65/35) (ammonium buffer/acetonitrile, v/v) for quinapril and quinaprilat, respectively at 45°C and flow rates of 0.4 and 0.5 mL min–1.