Separation and characterization of allergic polymerized impurities in cephalosporins by 2D-HPSEC × LC-IT-TOF MS

Two-Dimensional High-Performance Liquid Chromatography as a Powerful Tool for Bioanalysis: The Paradigm of Antibiotics

The technique of two-dimensional high-performance liquid chromatography has managed to gain the recognition it deserves thanks to the advantages of satisfactory separations it can offer compared to simple one-dimensional. This review presents in detail key features of the technique, modes of operation, and concepts that ensure its optimal application and consequently the best possible separation of even the most complex samples. Publications focusing on the separation of antibiotics and their respective impurities are also presented, providing information concerning the analytical characteristics of the technique related to the arrangement of the instrument and the chromatographic conditions.

Separation and characterization of the polymerized impurities in oxacillin sodium by 2D HPSEC and HPLC IT-TOF MS

RATIONALE

The polymerized impurities in oxacillin sodium can induce allergic reaction, which can seriously threaten the health of patients. Gel filtration chromatography (GFC) is currently widely used for the analysis of polymerized impurities, but it has drawbacks. To effectively control the polymerized impurities in oxacillin sodium, a high-performance size exclusion chromatography (HPSEC) method and a reversed-phase high performance liquid chromatography (RP-HPLC) method were established to replace the classical GFC method.

METHODS

By studying the chromatographic behavior of polymerized impurities and small molecular weight impurities in both methods with different chromatographic separation mechanisms, the polymerized impurities in oxacillin sodium were separated and detected effectively. Column-switching two-dimensional liquid chromatography was applied to eluted polymerized impurities from the HPSEC method for oxacillin sodium. Ion trap/time-of-flight mass spectrometry was applied to characterize the structures of polymerized impurities and unknown impurities eluted from the HPSEC/RP-HPLC method for oxacillin sodium.

RESULTS

The structures of 25 unknown impurities in oxacillin sodium were elucidated based on the high-resolution massⁿ data. Thirteen polymerized impurities were found and characterized. The corresponding relationship of impurities between the two methods was established and the specificity of the two methods was compared. The RP-HPLC method for analysis of the polymerized impurities not only has higher column efficiency and more specificity than the HPSEC method, but also higher sensitivity.

CONCLUSIONS

The mechanisms of the formation of degradation impurities in oxacillin sodium were studied. The newly established RP-HPLC methods could effectively separate and detect polymerized impurities and unknown impurities in oxacillin sodium. The study of the impurity profile in oxacillin sodium provided a scientific basis for the improvement of official monographs in pharmacopoeias.

Characterization of Allergic Polymerized Impurities in Cephalosporins by MALDI-TOF MS/MS Spectrometry

Background:

Characterization of allergic polymerized impurities in cephalosporins is significant to ensure the safety and quality of the products.

Objective:

To develop a MALDI-TOF MS/MS method to characterize the structures of polymerized impurities in cefuroxime axetil drug substance and cefetamet pivoxil drug substance.

Methods:

Calibrant references were TOF mix, including Angiotensin 2, Angiotensin 1, Glu-1-fibrino, N-Acetyl renin, ACTH 1-17, ACTH 18-39 and ACTH 7-38. Matrix was DHB at a concentration of 10 mg•mL-1. Acetone and water were used as solvent to dissolve cefuroxime axetil and cefetamet pivoxil hydrochloride drug substances, respectively. The prepared solutions were mixed with DHB, volatilized to dry, and subjected to MALDI-TOF MS/MS analysis, respectively. MS data was obtained in the linear mode with a power of 80, and MS2 data was obtained in the reflection mode with a power of 120. Molecular weights of polymerized impurities in cefuroxime axetil and cefetamet pivoxil were obtained based on the MS data. Their fragmentation patterns and structural assignments were studied based on the MS2 data.

Results:

Eight polymerized impurities in cefuroxime axetil drug substance and cefetamet pivoxil hydrochloride drug substance made in China were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS/MS), among which impurity Ⅰ-Ⅴ were in cefuroxime axetil and impurities Ⅵ-Ⅷ were in cefetamet pivoxil. Based on the experimental results, the polymerization mechanism of polymerized impurities in cephalosporins was discussed.

Conclusion:

MALDI-TOF MS/MS was proved to be simple, quick and sensitive for the analysis of polymerized impurities in cephalosporins.

Isolation and Characterization of An Allergic Dimer Impurity in Cefmenoxime Hydrochloride by NMR and HR-MS Method

Background:

We systematically characterized an allergic dimer impurity in cefmenoxime hydrochloride raw material by UV, IR, HR-MS, 1D and 2D NMR for the first time.

Methods:

The dimer stock solution of cefmenoxime hydrochloride was obtained by degradation method. The target dimer impurity in stock solution was separated by preparative RP-HPLC, and purified by freeze-drying method. The dimer’s functional groups corresponding to the characteristic peaks of UV and IR spectra were analyzed by comparison with cefmenoxime hydrochloride and its molecular formula and mass fragmentation pattern were deduced by HR-MS.

Results:

Then based on the full assignment of 1H and 13C NMR signals，the dimerized position was confirmed and its absolute configuration was identified by 1D and 2D NMR.

Conclusion:

This study provided a structural basis for the allergic study of dimer impurities in cephalosporin drugs.

Analysis of pharmaceutical drug oligomers by selective comprehensive two-dimensional liquid chromatography-high resolution mass spectrometry

The presence of oligomeric impurities in drugs is often overlooked and less studied due to conventional small molecule analytical methods which are often not capable of capturing these oligomers. In the present work, the oligomer species of a lipophilic active pharmaceutical ingredient (API) containing an azetidine ring was investigated. No separation was observed by reversed-phase liquid chromatography (RPLC) methods, and only a partial separation of oligomer peaks was achieved by a size exclusion chromatography (SEC) method. To improve the resolution of the different oligomers species and understand the root cause of the formation of the oligomers, a selective comprehensive two-dimensional liquid chromatography (2D-LC) method was developed by coupling SEC to RPLC. The selective comprehensive SEC × RPLC method allowed the separation of 16 species and evidenced four main groups of oligomer impurities. The contour plots of 3 API lots helped to visualize the oligomer profiles and quickly compare the difference between these lots. Finally, the oligomer peaks separated by 2D-LC were identified by high-resolution mass spectrometry (HRMS) using a Q Exactive mass spectrometer. The developed 2D-LC/HRMS workflow provides a fast and generic screening approach to quickly examine and visualize the oligomeric impurities in API materials, and direct the impurity control strategy during process development.

Study of the impurity profile and polymerized impurity in mezlocillin sodium by multiple heart-cutting two-dimensional liquid chromatography coupled with ion trap time-of-flight mass spectrometry

RATIONALE

Eleven impurities and one polymerized impurity in mezlocillin were identified and their formation mechanisms were investigated in this study. The sources and reasons for the formation of impurities were revealed, which may guide industry to improve the manufacturing process and storage conditions and reduce the content of impurities in products. The results from this study also provided a scientific basis for the improvement of official monographs in pharmacopoeias.

METHODS

The impurity profiles and polymerized impurity in mezlocillin were studied by multiple heart-cutting two-dimensional liquid chromatography coupled with ion trap time-of-flight mass spectrometry (2D-LC/IT-TOF MS) in both positive and negative modes of electrospray ionization. Target eluents from the first dimensional chromatography with a non-volatile mobile phase were trapped and sent to the second dimensional chromatography with a volatile mobile phase by a switching valve. The structures of the impurities in the mezlocillin drug substance were deduced based on the high-resolution MSⁿ data.

RESULTS

In the environment of water, oxygen, high temperature, acid and base, a series of degradation products could be easily produced from mezlocillin. Mezlocillin was hydrolyzed into impurities I, IV, V and X, and was degraded into impurity III by methanolysis. Mezlocillin was oxidized into sulfoxide by producing impurity XI. Furthermore, impurities VI, VII, VII and IX were all isomers of mezlocillin. The proposed formation pathways of these products were demonstrated in this study.

CONCLUSIONS

Eleven degradation impurities and one polymerized impurity in mezlocillin were separated and characterized. Based on characterization of impurities, this study discovered the mechanism of impurity production and provided guidance for manufacturers to improve the process and storage conditions and reduce levels of impurities.

Separation and characterization of allergenic polymerized impurities from cephalosporin for injection by trap free two-dimensional high performance size exclusion chromatography × reversed phase liquid chromatography coupled with ion trap time-of-flight mass spectrometry

As requested by regulatory authorities, polymerized impurities are an important issue of quality control. In this study, we presented the utilization of a trap-free two-dimensional chromatography, which was consisted by a high performance size exclusion chromatography (HPSEC) and a reversed-phase liquid chromatography (RP-LC) coupled to ion trap time-of-flight mass spectrometry with positive mode of electrospray ionization, to separate and characterize ten allergenic impurities in ceftazidime for injection, cefazolin sodium for injection, cefoperazone sodium and sulbactam sodium for injection and cefamandole nafate for injection. An effective method for characterizing the polymerized impurities in β-lactam antibiotics was established on the basis of column-switching technique which effectively combined the advantages of HPSEC and the ability of RP-HPLC to identify the special impurities. In the first dimension, the column was the Xtimate SEC-120 analytical column (7.8 mm × 30 cm, 5 μm) and the flow rate was 1.0 mL min^-1 with gradient elution using 0.005 mol L^-1 phosphate buffer solution at pH 7.0 and acetonitrile as mobile phase. In the second dimension, the analytical column was ZORBAX SB-C18 (4.6 × 150 mm, 3.5 μm) using ammonium formate solution (10 mM) and ammonium formate (8 mM) in [acetonitrile-water (4:1, v/v)] solution as mobile phase at a flow rate of 0.4 mL min^-1. Eluent associate with each peak separated in the first dimension was trapped by a 20 μL quantitative loop and then transferred (via a six-port valve) into the second dimension system with volatile mobile phase. Through the multiple heart-cutting 2D-LC approach and online desalting technique, the problem of incompatibility between non-volatile mobile phase and mass spectrometry was solved completely. The fragmentation behaviors of ten allergenic impurities were studied. The structures of ten allergenic impurities in cephalosporin drug substance were deduced based on the HPLC-MSⁿ data, in which four impurities were polymerized impurities. The forming factors of polymerized impurity in cephalosporins were also studied.