Objective: This research foucuses on the development of a liquid chromatographic method for the rapid and reliable separation and identification of major nitrosamine impurities, ensuring both short analysis time and adequate resolution. Given the toxicological relevance of nitrosamines, their occurrence in pharmaceutical formulations has raised substantial concerns, leading to the reassessment of multiple drug products. In response, reverse-phase HPLC with UV detection and LC-MS techniques have been widely applied as powerful analytical tools for their detection and control.
Methods: The following impurities of the N-nitrosamine class are separated and identified by the LC-MS technique: NDMA (N-nitrosodimethylamine), NDEA (N-nitrosodiethylamine), NMEA (N-nitrosomethylethylamine) NDIPA (N-nitrosodiisopropylamine), NDBA (N-nitrosodibutylamine) NPIP (N-nitrosopiperidine). A standard solution of nitrosamines mix was prepared and subsequently diluted in methanol to achieve a final concentration of 20 µg/mL for each compound. The analysis was performed using a UHPLC chromatography system Flexar FX10 (Perkin Elmer) with MS QTOF (AB Sciex TripleTOF4600), Phenomenex Luna Omega 3 C18 (150×4.6mm, 3μm) column, column temperature 450C, mobile phase methanol and formic acid 0.1% in ultrapure water, gradient elution, flow 0.45 mL/min., injected volume 5 µl. The proposed LC-MS conditions are significantly improved compared to the European Pharmacopoeia recommendations for N-Nitrosamines impurities in active substances analysis.
Results: Based on the mass fragmentation profiles of the six investigated nitrosamines, chromatographic separation was successfully accomplished in less than 25 minutes, with the elution sequence established as follows: NDMA, NMEA, NDEA, NPIP, NDIP, NDBA.
Conclusions: The development of optimal chromatographic conditions allows further separation and identification of nitrosamines impurities in pharmaceutical products.
Tag Archives: development
Aquaporin 2 Expression in Human Fetal Kidney Development
Introduction: The metanephrogenic zone, renal cortex and renal pyramids develop into their final form by week 13. The metanephric kidney produces large quantities of diluted urine in order to maintain volumes of amniotic fluid. Aquaporins are transmembrane protein channels that enable water transport through biological membranes. Aquaporin 2 (AQP2) is a water channel found in the supranuclear region and apical area of the cell membrane of the kidneys collecting tubule cells. Its main function is reabsorption of water through vasopressin stimulation.
Materials and methods: Immunohistochemistry was used to study fetal renal tissue of 34 post-mortem fetuses of 9 weeks to 24 weeks gestational age.
Results: AQP2 expression is present in connecting tubules and collecting tubules during the targeted time period. From week 9 to 12, the expression is cytoplasmic. From week 13 to 20 the enhancement of expression in the apical cell membrane occurs with the advancement of fetal age. At the end of the studied period, from week 21 to 24, both cytoplasmic and apical expression were observed. In animal studies AQP2 expression has an increasing trend during development. In contradiction with these results, other authors described low AQP2 levels in the human fetal kidney.
Conclusions: This study helps to understand the amniotic fluid’s homeostasis during pregnancy. In the beginning of the fetal period AQP2 protein is present in the cytoplasm of epithelial cells of the collecting duct and distal connecting duct. During the fetal period, AQP2 expression in collecting ducts becomes more enhanced in the apical membrane of the cells.