Reverse phase method development solubility

The stationary phase may be a solid or liquid on a solid support. The mechanisms responsible for distribution between phases include surface absorption, ion exchange, relative solubilities and steric affects . High performance liquid chromatography is a useful method for quinolizidine alkaloid analysis, especially when pure standards are available". This method was recently used for alkaloid metabolite extraction and analysis . A simple reversed-phase liquid chromatographic method has been developed for the simultaneous quantitation of four anticancerous alkaloids vincristine, vinblastine, and their precursors catharanthine and vindoline using a specific HPLC column . 

Counter-ions, usually small polar or ionic compounds, are routinely used to enhance the aqueous solubility and/or stability of the API. Because of their polarity, counter-ions are rarely resolved from the chromatographic solvent front in reversed-phase HPLC and have characteristically poor chromophores which makes detection difficult. The counter-ion can be omitted from the achiral method development sample set with minimal risk when this holds true. Analysis of counter-ions is normally performed using ion chromatography.9,10 This assay is separate from the reversed-phase assay performed to measure organic impurity levels. 

To begin this investigation, it was necessary to develop a method capable of accurately measuring PAH solubilities. In this method, saturated solutions are prepared by an equilibrium process and extracted almost instantaneously. Quantitative analyses of the extract are done by reverse-phase HPLC. Preparation, extraction, and analysis of the saturated solutions all occur within the same system. 

Nonaqueous suspension agents such as paraffin oils have been developed to polymerize polar monomers, such as acrylic acid. The so-called water-in-oil (W/O) suspension polymerization (reversed phase suspension polymerization) comprises an aqueous solution containing the hydrophilic monomer(s) and initiator(s), which are dispersed in a liquid paraffin oil or other nonpolar hydrocarbon media and polymerized. The use of perfluorocarbon fluids has extended the scope of the suspension polymerization method to monomers and initiators that cannot be used, due to their high solubility and reactivity, in conventional suspension media [249]. 

Although not a requisite for the selection of SFC as the purification technique of choice, highly lipophilic samples are preferable so as to avoid solubility problems often encountered in reverse-phase HPLC processing. It should be noted, however, that highly polar materials can be purified by SFC so long as materials can be dissolved at a level of 50m mL of methanol, along with co-solvents such as acetonitrile or dichloromethane. Further, when a synthetic chemist specifically requests that samples be returned in their non-TFA salt form, SFC is selected as it can be frequently developed in methanol/carbon dioxide or, alternatively, volatile small amine modifiers such as triethylamine. Finally, it is generally possible to achieve better resolution with an SFC rather than the HPLC method of our present setup, so in instances where a difficult separation of desired product is anticipated based on LC/MS analysis, SFC may be preferentially chosen over HPLC. 

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