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To determine the paclitaxel-related substances in a paclitaxel injection (albumin-bound), it is necessary to remove human blood albumin from the sample via solid-phase extraction and subsequently perform high-performance liquid chromatography analysis. The pre-processing operation is complicated, the duration of analysis is long, and much human power and material resources are needed in the sample testing process. Thus, the purpose of this study was to develop a quick two-dimensional liquid chromatography method that requires less consumables and possesses high sensitivity. Samples were directly injected into one-dimensional solid-phase extraction columns to remove human blood albumin. Paclitaxel and its related substances in the solid-phase extraction columns were then eluted into two-dimensional analytical columns through valve switching technology. The sample pretreatment step can be omitted in this method, which allows for the analysis of paclitaxel and its related substances to be completed more quickly, within only 15 min, under the developed two-dimensional elution conditions. The established method had good linearity (R2 = 0.9994), limit of detection (0.25 μg·mL−1), limit of quantification (0.5 μg·mL−1), precision (RSD = 0.5%), and accuracy (102.53–107.97%). [ABSTRACT FROM AUTHOR]

Sulfonate esters, one of the genetic impurities, have gained significant attention in recent years due to their potential to cause genetic mutations and cancer. In this study, we reported a novel on‐line column‐switching liquid chromatography method for the quantitative analysis of three p‐toluene sulfonate alkyl esters in active pharmaceutical ingredients (APIs). The sensitivity was improved by large‐volume injection. A diluting modulation‐based sampling procedure was specifically devised to mitigate the impact of solvent effects and resolve the poor stability of isopropyl p‐toluene sulfonate alkyl ester. The established method was validated in terms of linearity, sensitivity, accuracy, stability, and robustness. The limit of quantitation level was determined to be 1 ng/mL (equivalent to 1 ppm relative to 1 mg/mL API samples). Besides, the method was applied for four APIs Tosuloxacin toluene sulfonate, Lapatinib toluene sulfonate, Nirapalib toluene sulfonate, and Capecitabine. The recoveries of all target analytes in the four‐drug substances were within 89%–110%. The expanded uncertainties of the measurements ranged from 6.8% to 8.4% at a coverage level of k = 2 and a confidence level of approximately 95%. The method described in this paper was compared with other published literature, demonstrating its simplicity and ease of standardization which could be further applied in the quality control and safety assessment of drug substances. [ABSTRACT FROM AUTHOR]

Cystine-enriched food supplements are increasingly popular due to their beneficial health effects. However, the lack of industry standards and market regulations resulted in quality issues with cystine food products, including cases of food adulteration and fraud. This study established a reliable and practical method for determining cystine in food supplements and additives using quantitative NMR (qNMR). With the optimized testing solvent, acquisition time, and relaxation delay, the method exhibited higher sensitivity, precision, and reproducibility than the conventional titrimetric method. Additionally, it was more straightforward and more economical than HPLC and LC-MS. Furthermore, the current qNMR method was applied to investigate different food supplements and additives regarding cystine quantity. As a result, four of eight food supplement samples were found to be inaccurately labeled or even with fake labeling, with the relative actual amount of cystine ranging from 0.3% to 107.2%. In comparison, all three food additive samples exhibited satisfactory quality (the relative actual amount of cystine: 97.0–99.9%). Notably, there was no obvious correlation between the quantifiable properties (price and labeled cystine amount) of the tested food supplement samples and their relative actual amount of cystine. The newly developed qNMR-based approach and the subsequent findings might help standardization and regulation of the cystine supplement market. [ABSTRACT FROM AUTHOR]