Created with MindGenius Business 2005® Adsorption/Partition Chromatography Adsorption/Partition Chromatography Normal Phase Normal Phase Reversed Phase Reversed Phase

Created with MindGenius Business 2005® Adsorption/Partition Chromatography 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 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: T R increases with polarity of analyte Increasing the polarity of the mobile phase reduces elution time Optimisation normally consists of varying the mobile phase R=OH, CN, NH 2 & more

Created with MindGenius Business 2005® Reversed Phase 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: T R decreases with polarity of analyte Increasing the polarity of the mobile phase increases elution time Optimisation normally consists of varying the mobile phase R= C18, C8, Ph & more