Semi-preparative isolation and structural elucidation of an impurity in citalopram by LC/MS/MS.

Two impurities were detected in citalopram bulk drug substance by HPLC analysis. A new LC-ESI/MS method was developed for the identification of impurities. One of the impurities was found to be unknown and has not been reported previously. The structure of the unknown impurity was proposed on the basis of MS(n) data obtained using ion trap mass analyzer and accurate mass obtained using Q-TOF mass analyzer. The impurity was isolated by semi-preparative HPLC. The structure of the impurity was confirmed as 1-(1,1-bis (4-fluorophenyl)-1,3-dihydroisobenzofuran-5-yl)-4-(dimethylamino) butan-1-one hydrobromide by using NMR and IR spectroscopy.

Investigation of amodiaquine bulk drug impurities by liquid chromatography/ion trap mass spectrometry.

Three unknown impurities in an amodiaquine bulk drug sample were detected by reversed-phase high-performance liquid chromatography with ultraviolet detection (HPLC/UV). A liquid chromatography/tandem mass spectrometry (LC/MS(n)) method is described for the investigation of these impurities. Mass spectral data were acquired on an LCQ ion trap mass analyzer equipped with an electrospray ionization (ESI) source operated in positive ion mode. The fragmentation behavior of amodiaquine and its impurities has been studied. Based on the mass spectral data and the specifics of the synthetic route, the possible structures of these impurities were elucidated as 4-[(5-chloroquinolin-4-yl)amino]-2-(diethylaminomethyl)phenol (impurity I), 4-[(7-chloroquinolin-4-yl)-amino]phenol (impurity II) and 4-[(7-chloroquinolin-4-yl)amino]-2-(diethylaminomethyl)-N(1)-oxy]phenol (impurity III). The structures were confirmed by their independent synthesis and NMR spectral assignment.

Simultaneous determination of metoprolol succinate and amlodipine besylate in pharmaceutical dosage form by HPLC.

A simple, precise, specific and accurate reverse phase HPLC method has been developed for the simultaneous determination of metoprolol succinate (MS) and amlodipine besylate (AB) in tablet dosage form. The chromatographic separation was achieved on Hypersil BDS cyano (250 mm x 4.6 mm, 5 microm) column using PDA detector. The mobile phase consisting of buffer (aqueous triethylamine pH 3) and acetonitrile in the ratio of 85:15 (v/v) at a flow rate of 1.0 mL/min was used. The method was validated according to the ICH guidelines with respect to specificity, linearity, accuracy, precision and robustness.

Development and validation of UPLC method for determination of primaquine phosphate and its impurities.

With the objective of reducing analysis time and maintaining good efficiency, there has been substantial focus on high-speed chromatographic separations. Recently, commercially available ultra-performance liquid chromatography (UPLC) has proven to be one of the most promising developments in the area of fast chromatographic separations. In this work, a new isocratic reverse phase chromatographic method was developed using UPLC for primaquine phosphate bulk drug. The newly developed method is applicable for assay and related substance determination of the active pharmaceutical ingredient. The chromatographic separation of primaquine and impurities was achieved on a Waters Acquity BEH C18, 50 x 2.1mm, 1.7 microm column within a short runtime of 5 min. The method was validated according to the regulatory guidelines with respect to specificity, precision, accuracy, linearity and robustness. Forced degradation studies were also performed for primaquine phosphate bulk drug samples to demonstrate the stability indicating power of the UPLC method. Comparison of system performance with conventional HPLC was made with respect to analysis time, efficiency and sensitivity.

Isolation and structural identification of an impurity in fluconazole bulk drug substance.

Four impurities in fluconazole API sample obtained from a recently proposed synthetic process were detected by HPLC. One of the impurities was unknown having not been reported previously. This less polar unknown impurity was isolated from the crude sample of fluconazole bulk drug using semi-preparative HPLC. Structure of impurity was elucidated as 2-(2-(dimethylamino)-4-fluorophenyl)-1,3-di(3H-1,2,4-triazol-1-yl)propan-2-ol by using NMR spectroscopy(1H, 13C, 19F, 1H-1H, 1H-13C, HMBC and nOe) and mass spectrometry. The formation and synthesis of the impurity was discussed.

Characterization and quantitative determination of impurities in piperaquine phosphate by HPLC and LC/MS/MS.

Four impurities in piperaquine phosphate bulk drug substance were detected by a newly developed gradient reverse phase high performance liquid chromatographic (HPLC) method. These impurities were identified by LC/MS/MS. The structures of impurities were confirmed by spectroscopic studies (NMR and IR) conducted using synthesized authentic compounds. The synthesized reference samples of the impurity compounds were used for the quantitative HPLC determination. The system suitability of HPLC analysis established the validity of the separation. The method was validated according to ICH guidelines with respect to specificity, precision, accuracy and linearity. Forced degradation studies were also performed for piperaquine phosphate bulk drug samples to demonstrate the stability indicating power of the newly developed HPLC method.

Preparative isolation and structural elucidation of impurities in fluconazole by LC/MS/MS.

Three impurities were detected in the LC/MS analysis of fluconazole bulk drug substance. Two of the impurities were unknowns having not been reported previously. Structural assignment of these impurities was carried out by LC/MS/MS using electrospray ionization source and an ion trap mass analyzer. Structural elucidation using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy was facilitated by newly developed rapid preparative isolation method. These impurities were characterized as 1-(1-H-1,2,4-triazole-1-yl) propane-2,3-diol and Z-2-(2,4-difluorophenyl)-3-(1-H-1,2,4-triazole-1-yl)-2-propen-1-ol. Their formation and synthesis are discussed.

Application of GC-EI-MS for the identification and investigation of positional isomer in primaquine, an antimalarial drug.

A major impurity associated with primaquine drug samples obtained from European Pharmacopoeia (EP) and other commercial sources was detected and identified using HPLC, photo diode array (PDA), LC-MS/MS and gas chromatograph-electron impact-mass spectrometer (GC-EI-MS). PDA and LC-ESI-MS/MS data provided an evidence for it being isomeric in nature. However, spectral data obtained from the newly developed GC-EI-MS method has been utilised for structural elucidation and found to be conclusive to characterize this impurity as positional isomer, i.e. 8-(4-amino-4-methylbutyl amino)-6 methoxyquinoline. The structure of this impurity has been confirmed by its synthesis. Precursor of primaquine was also investigated using GC-EI-MS. The data obtained confirmed the origin of isomeric impurity in precursor.