Application of a trap-free two-dimensional liquid chromatography combined with ion trap/time-of-flight mass spectrometry for separation and characterization of impurities and isomers in cefpiramide

Two-dimensional liquid chromatography with reversed phase in both dimensions: A review

Two-dimensional liquid chromatography (2D-LC), and in particular comprehensive two-dimensional liquid chromatography (LC×LC), offers increased peak capacity, resolution and selectivity compared to one-dimensional liquid chromatography. It is commonly accepted that the technique produces the best results when the separation mechanisms in the two dimensions are completely orthogonal; however, the use of similar separation mechanisms in both dimensions has been gaining popularity as it helps avoid difficulties related to mobile phase incompatibility and poor column efficiency. The remarkable advantages of using reversed phase in both dimensions (RPLC×RPLC) over other separation mechanisms made it a promising technique in the separation of complex samples. This review discusses some physical and practical considerations in method development for 2D-LC involving the use of RP in both dimensions. In addition, an extensive overview is presented of different applications that relied on RPLC×RPLC and 2D-LC with reversed phase column combinations to separate components of complex samples in different fields including food analysis, natural product analysis, environmental analysis, proteomics, lipidomics and metabolomics.

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.

Structural confirmation of synthetic cannabinoids in seized electronic cigarette oil: A combined mass spectrometric and computational study

RATIONALE

Synthetic cannabinoids are some of the most used and abused new psychoactive substances, because they can produce a stronger intense pleasure than natural cannabis. Most of the new synthetic cannabinoids are structurally similar to existing synthetic cannabinoids and can be obtained by modifying partial structures of the latter without changing their effects. Therefore, the derivatization rules and common fragmentation patterns of synthetic cannabinoids could be used for rapid screening and structural identification of them.

METHODS

The derivatization rules of synthetic cannabinoids are summarized, and the common fragmentation pattern of synthetic cannabinoids including three typical cleavage pathways was explored and extended in this work based on combined mass spectrometry (MS) and density functional theory studies. Five synthetic cannabinoids in electronic cigarette oil from a drug case were separated and characterized using gas chromatography with MS and liquid chromatography coupled to high-resolution quadrupole Orbitrap MS.

RESULTS

The structures of five synthetic cannabinoids in seized electronic cigarette oil were deduced from electron impact ion source (EI) MS and high-resolution electrospray ionization (ESI) MSⁿ data, along with the derivatization rules and common fragmentation pattern of synthetic cannabinoids. The proposed structures of these synthetic cannabinoids were further verified via reference substances. Computational study showed that selective cleavage of these compounds was mainly controlled by spin population in EI-MS, but a tunneling effect arose from proton transfer in ESI-MSⁿ detection, which has been rarely reported in previous works.

CONCLUSIONS

Our results showed that EI-MS was suitable for identifying synthetic cannabinoids with aromatic ketone structure, which could also be extended to adamantane linked group. Nevertheless, synthetic cannabinoids with carbamoyl linked group were better characterized by high-resolution ESI-MSⁿ compared to EI-MS. This study demonstrated a method with promising potential for rapid and reliable screening of synthetic cannabinoids in mixtures with enhanced detection throughput and operation simplicity.

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.

Impurity profile and spectrum characteristics of the isomers in cefamandole nafate using high- performance liquid chromatography/high-performance size exclusion chromatography tandem ion trap/time-of-flight mass spectrometry

RATIONALE

Reversed-phase, high-performance liquid chromatography (RP-HPLC) and high-performance size exclusion chromatography (HPSEC) methods were developed to effectively separate unknown impurities and polymerized impurities in cefamandole nafate. The liquid chromatography-tandem ion trap/time-of-flight mass spectrometry (LC-IT-TOF-MS) was applied to characterize the structures of the impurities. Ultraviolet (UV) spectrum characteristics and mass spectrum characteristics of △³ -isomer and 7-epimer in cefamandole nafate were studied to distinguish the isomers.

METHODS

RPLC-IT-TOF-MS was used to characterize the structures of unknown impurities and polymerized impurities eluted from the C₁₈ column. On this basis, the two-dimensional (2D) HPSEC-IT-TOF-MS was used to confirm the structures of polymerized impurities eluted from the TSK-gel G2000SWxl column. Complete fragmentation patterns of impurities were studied and used to obtain information about the structures of the impurities.

RESULTS

The structures of 19 unknown impurities in cefamandole nafate were elucidated based on the high-resolution MSⁿ data with both positive and negative modes, assisted by the UV spectra and stress testing, of which 2 impurities were polymerized impurities. Cefamandole nafate produced a series of degradation impurities, and another principal component cefamandole acid also produced a series of similar degradation impurities. The disciplines between mass fragmentation pattern/UV spectrum and structure for △³ -isomer and 7-epimer were presented to distinguish their structures.

CONCLUSIONS

The results of this study provided a scientific basis for the improvement of official monographs in pharmacopoeias to effectively control the impurities and ensure drug safety for the public. This study also revealed the formation mechanisms of degradation impurities in cefamandole nafate, which may guide industry to improve the manufacturing process and storage conditions to reduce the content of impurities in products.

An Overview of Advances in the Chromatography of Drugs Impurity Profiling

A systematic literature survey published in several journals of pharmaceutical chemistry and of chromatography used to analyze impurities for most of the drugs that have been reviewed. This article covers the period from 2016 to 2020, in which almost of chromatographic techniques have been used for drug impurity analysis. These chromatography techniques are important in the analysis and description of drug impurities. Moreover, some recent developments in forced impurity profiling have been discussed, such as buffer solutions, mobile phase, columns, elution modes, and detectors are highlighted in drugs used for the study. This primarily focuses on thorough updating of different analytical methods which include hyphenated techniques for detecting and quantifying impurity and degradation levels in various pharmaceutical matrices.

Separation and structural elucidation of cefsulodin and its impurities in both positive and negative ion mode in cefsulodin sodium bulk material using liquid chromatography/tandem mass spectrometry

RATIONALE

The structural identification of impurities in cephalosporins has been reported. However, to the best of our knowledge, there was no report on the impurities of cefsulodin sodium, which is necessary for the quality control. Thus, the aim of this study was to separate and characterize the impurities in cefsulodin sodium raw material using liquid chromatography/tandem mass spectrometry (LC/MS/MS).

METHODS

The analytes were separated on a Kromasil 100-5C18 column (4.6 mm × 250 mm, 5 μm) using a gradient elution with a mobile phase consisting of 1% ammonium sulphate aqueous solution and acetonitrile in the first dimension. The separation in the second dimension was carried on a Shimadzu Shim-pack GISS C18 column (50 mm × 2.1 mm, 1.9 μm) with a mobile phase consisting of 10 mM ammonium formate solution and methanol.

RESULTS

The fragmentation behaviors of cefsulodin and its impurities were studied and the structures of the impurities were deduced based on the MSⁿ data. The structures of ten unknown impurities were proposed based on the work carried out in this study. The degradation behaviors of cefsulodin sodium were also studied. This revealed that cefsulodin sodium should be stored in a dry, cool and dark closed container.

CONCLUSIONS

Based on the characterization of impurities, this study not only revealed the mechanism by which impurities were produced, thus providing guidance to pharmaceutical companies for manufacturing process improvement and impurity control, but also provided a scientific basis for further improvement of official monographs in pharmacopoeias.

Green and efficient degradation of cefoperazone sodium by Bi4O5Br2 leading to the production of non-toxic products: Performance and degradation pathway

Photocatalytic process represents a promising approach to overcome the pollution challenge associated with the antibiotics-containing wastewater. This study provides a green, efficient and novel approach to remove cephalosporins, particularly cefoperazone sodium (CFP). Bi₄O₅Br₂ was chosen for the first time to systematically study its degradation for CFP, including the analysis of material structure, degradation performance, the structure and toxicity of the transformation products, etc. The degradation rate results indicated that Bi₄O₅Br₂ had an excellent catalytic activity leading to 78% CFP removal compared with the pure BiOBr (38%) within 120 min of visible light irradiation. In addition, the Bi₄O₅Br₂ presents high stability and good organic carbon removal efficiency. The effects of the solution pH (3.12 - 8.75) on catalytic activity revealed that CFP was mainly photocatalyzed under acidic conditions and hydrolyzed under alkaline conditions. Combined with active species and degradation product identification, the photocatalytic degradation pathways of CFP by Bi₄O₅Br₂ was proposed, including hydrolysis, oxidation, reduction and decarboxylation. Most importantly, the identified products were all hydrolysis rather than oxidation byproducts transformed from the intermediate of β-lactam bond cleavage in CFP molecule, quite different from the mostly previous studies. Furthermore, the final products were demonstrated to be less toxic through the toxicity analysis. Overall, this study illustrates the detailed mechanism of CFP degradation by Bi₄O₅Br₂ and confirms Bi₄O₅Br₂ to be a promising material for the photodegradation of CFP.

Study of the impurity profile and characteristic fragmentation of Δ3 -isomers in cephapirin sodium using dual liquid chromatography coupled with ion trap/time-of-flight mass spectrometry

RATIONALE

According to the requirements of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), the structures of impurities in pharmaceutical products present at over 0.1% need to be confirmed. Therefore, the aim of this study is to separate and identify the impurities in cephapirin sodium drug substances, so as to guide the industry to improve the production process and storage conditions and reduce the amount of impurities in the product.

METHODS

In the first chromatography dimension, a Boston Green ODS (4.6 mm × 250 mm, 5 μm) column was used, with a mobile phase composed of 0.05 M sodium dihydrogen phosphate aqueous solution and acetonitrile. In the second dimension, the column was a Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 μm), using 10 mM ammonium formate solution and methanol as the mobile phase.

RESULTS

The fragmentation behavior of cephapirin and its impurities and isomers was studied and the structures of impurities were deduced based on the MSⁿ data. For six unknown impurities tentative structures were proposed. The degradation behavior of cephapirin sodium was also studied. Impurities 1 to 11 were found in commercial cephapirin sodium samples, indicating that cephapirin sodium should be stored in closed containers.

CONCLUSIONS

The contradiction between the non-volatile mobile phase and mass spectrometry was solved by means of multiple heart-cutting approaches and an on-line desalting technique. Twelve impurities and isomers were separated and characterized. These results could be used to improve the methods described in pharmacopoeias for the quality control of cephapirin sodium.

Development of a fragmentation pattern of synthetic cannabinoids based on electrospray ionization mass spectrometry in positive ion mode to screen synthetic cannabinoids in illicit products

To explore the MS fragmentation pattern of synthetic cannabinoids by electrospray ionization mass spectrometry, twenty-seven synthetic cannabinoids were systematically investigated by liquid chromatography coupled to high-resolution quadrupole Orbitrap mass spectrometry(LC-Q-Orbitrap/MS)with positive mode of electrospray ionization. Based on tandem multistage MS and high resolution MS data, MS fragmentation pattern of synthetic cannabinoids was summarized. The cleavage of CC bonds next to the oxygen at the side chain on the C-3 position of synthetic cannabinoids was the characteristic fragmentation pathway of synthetic cannabinoids in the positive mode of electrospray ionization. When the synthetic cannabinoids with a 3-carbamoylpropyl-indole/indazole structure, NH₃, CO, NH₂CHO and CH₂(CH₃)₂ were easy to lose to form different ions. While when the synthetic cannabinoids with a 3-carboxamide-indole/indazole structure, the side chain on the C-3 position was susceptible to γ-cleavage. In addition, this MS fragmentation pattern was applied to quickly screen whether electronic cigarette oil and tobacco from drug cases contain synthetic cannabinoids. This kind of compounds had strong fragmentation pattern, which provided new evidence for the rapid structure identification of synthetic cannabinoids.

Characterization of four unknown impurities in azithromycin and erythromycin imino ether using two-dimensional liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry and nuclear magnetic resonance

RATIONALE

A simple and sensitive method was developed for the separation and characterization of four unknown impurities in azithromycin and erythromycin imino ether using two-dimensional liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry (2D LC/QTOFMS) with positive and negative electrospray ionization.

METHODS

The chromatographic separation in the first dimension was performed with a Waters Xbridge RP18 column in gradient mode using binary mobile phase: (A) phosphate buffer (pH 8.2)-acetonitrile (47:53, v/v) and (B) water-acetonitrile (90:10, v/v). In the second dimension, the chromatographic separation was performed using a Shimadzu Shim-pack GISS C18 column with volatile mobile phases: (A) ammonium formate solution (10 mM) and (B) methanol.

RESULTS

The molecular formulae and structures of the four impurities were deduced based on the LC/MS/MS data, and further confirmed using ¹ H NMR, ¹³ C NMR, ¹ H-¹ H COSY, HSQC and HMBC NMR spectra after semi-preparative isolation of impurities. In addition, the mechanism for the formation of the impurities was also proposed.

CONCLUSIONS

The contradiction between the non-volatile salt mobile phase and mass spectrometry was solved by means of a multiple heart-cutting 2D LC approach and on-line desalination technology. Four impurities were separated and characterized. These results could further improve the method of official monographs in pharmacopoeias and guides to improve the process of reducing impurity content.

Separation and characterization of unknown impurities in rutin tablets using trap-free two-dimensional liquid chromatography coupled with ion trap/time-of-flight mass spectrometry

RATIONALE

A new high-performance liquid chromatography method was developed for the determination of impurities in rutin tablets to improve on the method of the official monograph in national drug standards. Five impurities in rutin tablets were characterized using trap-free two-dimensional liquid chromatography coupled with ion trap/time-of-flight mass spectrometry (2D-LC/IT-TOFMS) in both positive and negative ion modes of electrospray ionization.

METHODS

In the first dimension, the LC column was a Thermo Acclaim 120™ C18 (4.6 mm × 250 mm, 5 μm), and the mobile phase was composed of 0.1 M sodium dihydrogen phosphate aqueous solution (pH adjusted to 4.4 with phosphoric acid) and acetonitrile (80:20, v/v). In the second dimension, the column was a Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 μm), and the mobile phase was composed of 10 mM ammonium formate solution and methanol.

RESULTS

The structures of five impurities in rutin tablets were deduced based on the MS ⁿ data in both positive and negative ion modes, in which two impurities were unknown. Impurity 1, impurity 2 and impurity 3 were proposed as flavonol 3,7-di-O-glycoside, flavonol mono-O-triglycoside and quercetin 3-O-glycoside, respectively, and impurity 4 and impurity 5 were proposed as kaempferol 3-O-rhamnosylglucoside and isorhamnetin 3-O-rhamnosylglucoside, respectively.

CONCLUSIONS

The method established in this study was simple and reliable for the routine quality control of rutin tablets. The contradiction between non-volatile salt mobile phase and mass spectrometry was solved by means of a multiple heart-cutting 2D-LC approach and on-line desalination technology. Five impurities were separated and characterized. These results provide a scientific basis for further improving the national drug standard of rutin tablets.

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.

Characterization of an Unknown Impurity in Glucosamine Sulfate Sodium Chloride by HPLC-Q-TOF MS and NMR

Background:

Glucosamine sulfate sodium chloride (glucosamine-SP) is mainly used for the treatment of osteoarthritis. During quality control of glucosamine-SP capsules, an unknown impurity was detected. Another unknown degradation product was generated together with above-mentioned impurity in heat condition.

Objective:

The study aimed to characterize an unknown impurity in glucosamine-SP capsules.

Methods:

A new volatile HPLC method compatible with mass spectrometry detection was set up. An amino column at 35 °C with a mobile phase consisting of water and acetonitrile (20: 80, v/v) was used at a flow rate of 1.5 ml/min at 297 nm. High-performance liquid chromatography quadrupole time-offlight mass spectrometry (HPLC-Q-TOF MS) was used to identify the impurity with the electrospray ionization (ESI) source in the positive ionization mode.

Results:

The results of HPLC-Q-TOF MS analysis indicated that the protonated molecule ions [M + H]+ of the unknown impurity and the novel degradation product were both at m/z 287. Preparative LC method was put into practice with a Prep-C18 column with a mobile phase consisting of water and acetonitrile (99: 1, v/v) at a flow rate of 20.0 ml/min at 297 nm. The assignment of the 1D and 2D NMR signals was performed for the unknown impurity. In addition, the formation of impurities was also studied.

Conclusion:

An unknown impurity and a degradation product in glucosamine-SP capsules were characterized. They were assigned as (1R, 2S, 3R)-1-(5-((S, E)-3, 4-dihydroxybut-1-en-1-yl) pyrazin-2-yl) butane-1, 2, 3, 4-tetraol and (1R, 2S, 3R)-1-(5-((S, Z)-3, 4-dihydroxybut-1-en-1-yl) pyrazin-2-yl) butane- 1, 2, 3, 4-tetraol.

Multi-Steps Fragmentation-Ion Trap Mass Spectrometry Coupled to Liquid Chromatography Diode Array System for Investigation of Olaparib Related Substances

A high-performance liquid chromatography-diode array-mass spectrometric (LC-DAD-MS) method was developed and validated to investigate the related substances of olaparib (OLA) in bulk form. OLA was exposed to acid–base hydrolysis, boiling, oxidation with hydrogen peroxide, and UV light followed by LC-DAD-MS analysis. OLA and OLA-related substances were simultaneously and quantitatively monitored by DAD at 278 nm and triple quadrupole mass spectrometry (QQQ-MS). The investigated compounds were auto-scanned by an ion trap MS which applied positive and negative modes separately. The fragmentation pathway was confirmed by applying multi-steps fragmentation to identify the resulted cleaved ions and their parent ion. OLA was found to be sensitive to the alkaline hydrolysis and less sensitive to UV light. Two major hydrolytic degradation products, including the protonated molar ions m/z 299 and m/z 367, were identified. Three potential impurities were also characterized. The LC-MS limit of detection (LOD) and limit of quantification (LOQ) were 0.01 and 0.05 ng/µL, respectively. The quantitative results obtained by LC-DAD was comparable with that of LC-QQQ-MS. The proposed method shows good intra-day and inter-day precision with relative standard deviation (RSD) <2%.

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.