Structural elucidation of process-related impurities in escitalopram by LC/ESI-MS and NMR.

Three impurities were detected in escitalopram bulk drug by HPLC-UV and LC/MS. These impurities were marked as ESC-I, -II and -III. Two of these impurities (ESC-II and -III) were unknown and have not been reported previously. Ion trap and Q-TOF mass analyzer were employed to carry out MS/MS and accurate mass analysis of these unknown impurities. Based on mass spectrometric data and synthetic specifics the structures of ESC-II and -III were proposed as N-(chloromethyl)-3-[5-cyano-1-(4-fluorophenyl)-1,3-dihydro-2-benzofuran-1-yl]-N,N-dimethylpropan-1-aminium and N-(chloromethyl)-4-[4-cyano-2-(hydroxymethyl)phenyl]-4-(4-fluorophenyl)-4-hydroxy-N,N-dimethylbutan-1-aminium respectively. The impurities were isolated by semi-preparative HPLC and structures were confirmed by NMR spectroscopy. The plausible mechanism for the formation of impurities is also discussed.

Structural elucidation of a process-related impurity in ezetimibe by LC/MS/MS and NMR.

A major process-related impurity associated with the synthesis of ezetimibe was detected by LC-MS. The isolated impurity was found not to have been previously reported. Based on LC/MS/MS studies and accurate mass data, the structure of that impurity was proposed to be 2-(4-hydroxybenzyl)-N,5-bis-(4-fluorophenyl)-5-hydroxypentanamide. The postulated structure was unambiguously confirmed with the help of the NMR and IR analyses of a synthetically obtained sample. The chemical shift of the labile proton of that new entity was assigned by a 2D-NOESY NMR experiment. A rationalization for the formation of this impurity is provided.

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.

Identification and characterization of process related impurities in chloroquine and hydroxychloroquine by LC/IT/MS, LC/TOF/MS and NMR.

The focus of this study is identification and characterization of major unknown impurities in chloroquine (CQ) and hydroxychloroquine (HCQ) bulk drug samples using liquid chromatography/ion trap mass spectrometry (LC/IT/MS) and liquid chromatography/time of flight mass spectrometry (LC/TOF/MS). The newly developed LC/MS method was employed for the analysis of both the drugs. The analysis revealed the presence of two impurities in each of the drugs. The impurities are designated as CQ-I, CQ-II (for chloroquine); HCQ-I and HCQ-II (for hydroxychloroquine). Three of the impurities, CQ-II, HCQ-I and HCQ-II were unknown have not been reported previously. Accurate masses of the impurities were determined by using Q-TOF mass spectrometer and fragmentation behavior was studied by an ion trap mass spectrometer. Based on the spectrometric data and synthetic specifics the structures of CQ-II, HCQ-I and HCQ-II were proposed as 1,4 pentanediamine, N(4)(7-chloro-4-quinolinyl), N(4)-chloromethyl, N(4)-ethylamine; 2-(4-(7-chloroquinolin-4-ylamino) pentylamino) ethanol and [[4-[(7-chloro-4-quinolyl) amino] N-pentyl] N-chloromethyl-N-ethylamino] ethanol respectively. The impurities were isolated by semi-preparative HPLC and structures were confirmed by NMR spectroscopy. The formation and through characterization of known CQ-I impurity is also discussed.

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.