Micellar liquid chromatographic green enantioseparation of racemic amino alcohols and determination of elution order

Development of HPLC system that uses phase-separation multiphase flow as an eluent

We developed a new type of HPLC system that uses phase-separation multiphase flow as an eluent. A commercially available HPLC system with a packed separation column filled with octadecyl-modified silica (ODS) particles was used. First, as preliminary experiments, 25 kinds of mixed solutions of water/acetonitrile/ethyl acetate and water/acetonitrile were supplied to the system to act as eluents at 20 °C. 2,6-Naphthalenedisulfonic acid (NDS) and 1-naphthol (NA) mixture was used as a model and mixed analyte was injected into the system. Roughly speaking, they were not separated in organic solvent-rich eluents and well separated in water-rich eluents, in which NDS eluted faster than NA. This means that HPLC worked under a reverse-phase mode for separation at 20 °C. Next, the separation of the mixed analyte was examined on HPLC at 5 °C, and then after judging the results, four kinds of ternary mixed solutions were in detail as eluents on HPLC at 20 °C and 5 °C. Based on their volume ratio, the ternary mixed solutions acted as a two-phase separation mixed solution, leading to a phase-separation multiphase flow. Consequently, the solutions flowed homogeneously and heterogeneously in the column at 20 °C and 5 °C, respectively. For example, the ternary mixed solutions containing water/acetonitrile/ethyl acetate at volume ratios of 20:60:20 (organic solvent-rich) and 70:23:7 (water-rich) were delivered into the system as eluents at 20 °C and 5 °C. In the organic solvent-rich eluent, the mixture of NDS and NA was not separated at 20 °C but was separated at 5 °C, the elution of NA being faster than the one of NDS (phase-separation mode). In the water-rich eluent, the mixture of analytes was separated at both 20 °C and 5 °C, the elution of NDS being faster than the one of NA. The separation at 5 °C was more effective than at 20 °C (reverse-phase mode and phase-separation mode). This separation performance and elution order can be attributed to the phase-separation multiphase flow at 5 °C.

Green Stability Indicating Organic Solvent-Free HPLC Determination of Remdesivir in Substances and Pharmaceutical Dosage Forms

A green liquid chromatographic method is considered in this work to minimize the environmental impact of waste solvents. One important principle is to replace or eliminate the use of hazardous organic solvents. Organic impurities in any active pharmaceutical ingredient could arise either during the process of its synthesis, or as degradation products developed throughout the shelf-life. Remdesivir (RDS) is an antiviral drug, approved by the US Food and Drug Adminstration (-FDA), to treat SARS-Cov-2 virus during its pandemic crisis. We studied the stability of remdesivir against several degradation pathways using the organic solvent-free liquid chromatographic technique. Separation was performed on RP-C18 stationary phase using mixed-micellar mobile phase composed of a mixture of 0.025 M Brij-35, 0.1 M sodium lauryl sulfate (SLS), and 0.02 M disodium hydrogen phosphate, adjusted to pH 6.0. The mobile phase flow rate was 1 mL min−1, and detection was carried out at a wavelength of 244 nm. We profiled the impurities that originated in mild to drastic degradation conditions. The method was then validated according to International Conference of Harmonization (ICH) guidelines within a linearity range of 5–100 μg mL−1 and applied successfully for the determination of the drug in its marketed dosage form. A brief comparison was established with reported chromatographic methods, including a greenness assessment on two new metrics (GAPI and AGREE). This study is the first to be reported as eco-friendly, solvent-free, and stability indicating LC methodology for RDS determination and impurity profiling.