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Adsorption/Partition Chromatography Normal Phase Reversed Phase Created with MindGenius Business 2005® Adsorption/Partition Chromatography Choosing mobile and stationary phases Stationary phase must have a similar polarity to the analyte Mobile phase is of substantially different polarity Polarity Series In general, polarity of organic compound in increasing order is: Alkyl < alkenyl < aromatic < halides < sulfides < ethers < nitro < esters ~ aldehydes ~ ketones < alcohols ~ amines < sulphones < sulphoxides < amides < carboxylic acids < phosphates < water Bold means that these groups can also be substantially affected by pH changes NB Avoid conditions that could decompose the analyte Created with MindGenius Business 2005® Normal Phase Stationary phase: normally a solid Analyte adsorbs to the stationary phase Packing is usually Silica or Alumina and is therefore polar Mobile phase: normally organic (i.e. not aqueous) wide choice of mobile phase Retention: TR increases with polarity of analyte Increasing the polarity of the mobile phase reduces elution time Optimisation normally consists of varying the mobile phase H3C O Si Si Si Si Si H3C H3C O Si R R H3C R=OH, CN, NH2 & more Created with MindGenius Business 2005® Reversed Phase Stationary phase: normally a liquid Analyte dissolves in the stationary phase Packing is usually modified Silica or Alumina Mobile phase: normally aqueous, plus MeOH orMeCN wide choice of mobile phase buffers Retention: TR decreases with polarity of analyte Increasing the polarity of the mobile phase increases elution time Optimisation normally consists of varying the mobile phase H3C O Si Si Si Si Si H3C H3C O Si R R H3C R= C18, C8, Ph & more Created with MindGenius Business 2005®