Separation and Characterization of New Components and Impurities in Leucomycin by Multiple Heart-Cutting Two-Dimensional Liquid Chromatography Combined with Ion Trap/Time-of-Flight Mass Spectrometry

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.

Quantitative analysis of impurities in leucomycin bulk drugs and tablets: A high performance liquid chromatography-charged aerosol detection method and its conversion to ultraviolet detection method

Toxic impurities were found in leucomycin and its preparation, however the content determination of impurities was challengeable due to the lacking of their reference standards. In this study, we developed high-performance liquid chromatography method coupled with charged aerosol detection (CAD) for the quantification of related substance of leucomycin (kitasamycin) bulk drugs and tablets, however, the CAD was not yet popular. In order to carry out quantitation work conveniently in the laboratory without CAD instruments, a high-performance liquid chromatography method coupled with ultraviolet (UV) detection was developed with the assistant of the HPLC-CAD results. The relative response of impurities on CAD chromatogram was used for guiding the establishment of HPLC-UV method, which could achieve the quantitation task in the absence of impurity reference standards. The developed HPLC-UV method was validated according to the ICH guideline and showed good precision, reproducibility and linearity with determination coefficient higher than 0.9999. The limit of detection and quantitation were 0.3 and 0.5 μg mL^-1, respectively. The recoveries were 92.9 %-101.5 % at the spiked concentration levels of 0.1 %, 0.8 %, 1.0 and 1.2 % with relative standard deviations (RSDs, n = 3) lower than 2.0 %. Finally, the developed HPLC-CAD and -UV methods were compared by the determination of impurities in several batches of leucomycin bulk drugs and tablets. The results demonstrated that the developed HPLC-UV method was simple and reliable. This study developed methods to quantify the related substance in leucomycin and tablets, and discussed a strategy of the conversion of HPLC-CAD method to HPLC-UV method. The developed methods could be considered for implementation into pharmacopeial monographs in the future.

Challenges, Progress and Promises of Impurities Annotation for LCMSIT- TOF

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Analysis of pharmaceutical products, as well as their active and inactive ingredients, and identification and characterization of potential impurities originating from raw materials and manufacturing processes is of importance in the field, especially for further assessment of potential positive or negative effects on the human body. In addition to expected therapeutic effects, unfortunately, some unwanted or adverse effects were encountered in the past, resulting in dramatic cases sometimes. These challenges have been overcome with the use of sophisticated and high-end analytical techniques today by focusing on developing more efficient, more accurate, more accessible, and faster determination techniques.

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One of the powerful techniques utilized under the given aim, especially for qualitative purposes, is the Time of Flight (TOF) based Mass Spectrometry (MS). Among the TOF-MS instruments, liquid chromatography- mass spectrometry-ion trap-time of flight (LCMS-IT-TOF) has a unique MSn capability, which is a versatile tool in exact mass prediction and structure elucidation. In this review, LCMS-ITTOF has been considered taking all aspects to account for its use in qualitative impurity profiling, and a retrospective view on previous studies was presented in an analytical manner.

Universal response method for the quantitative analysis of multi-components in josamycin and midecamycin using liquid chromatography coupled with charged aerosol detector

Josamycin and midecamycin are consisted of three groups of components with different ultraviolet maximum absorption wavelengths (λ_max), which are 231 nm, 280 nm and 205 nm. The quantitative analysis of all these components is challengeable due to the absence of the respective reference substances. To address this problem, universal and reliable methods were developed using high performance liquid chromatography coupled with charged aerosol detector (HPLC-CAD) for the quantitative analysis of components in josamycin and midecamycin. The chromatographic conditions and CAD parameters setting were optimized. Subsequently, the components were identified using HPLC coupled with ion trap/time-of-flight mass spectrometry (IT/TOF MS). The developed methods were validated by assessing linearity, limit of quantitation (LOQ), accuracy, precision and robustness. Good separations were achieved for all components and the adjustment of the filter valve and power function value efficiently improved sensitivity. The developed methods were more comprehensive than current HPLC-UV method. The experimental results demonstrated good linearity with coefficients of determination (R²) greater than 0.999 in the range of 0.002-0.30 mg mL^-1. The limits of detection (LOD) were ranging from 1.8 to 2.0 μg·mL^-1. The intra-day and inter-day RSD values were less than 2.0 % (n = 6) and 5.6 % (n = 9) respectively. The recoveries were 95.0 %-124.0 % at the spiked concentration levels of 0.05 %, 0.50 %, 0.10 % and 2.5 % with relative standard deviations (RSDs, n = 3) lower than 2.0 %. Finally, the developed methods were successfully applied to the quantitative analysis of minor components and used main components (leucomycin A₃ and midecamycin A₁) as alternative reference substance of minor components. The overall results demonstrated that the HPLC-CAD was a good alternative for the quantitative analysis of multi-components in 16-membered macrolides.

Current developments in LC-MS for pharmaceutical analysis

Liquid chromatography (LC) based techniques in combination with mass spectrometry (MS) detection have had a large impact on the development of new pharmaceuticals in the past decades.