Determinations of gas-liquid partition coefficients using capillary chromatographic columns. Alkanols in squalane

M. TASCON, L. M. ROMERO, A. ACQUAVIVA, S. KEUNCHKARIAN, C. CASTELLS

JOURNAL OF CHROMATOGRAPHY - A

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 1294 p. 130 - 136

0021-9673

This  study  focused  on  an  investigation  into  the  experimental  quantities  inherent  in  the  determination of partition coefficients from gas?liquid chromatographic measurements through the use of capillary columns.  We  prepared  several  squalane  ?  (2,6,10,15,19,23 hexamethyltetracosane)  ?  containing  columnswith  very  precisely  known  phase  ratios  and determined  solute  retention  and  hold-up  times  at  30,  40,50  and  60 ◦C.  We  calculated infinite  dilution  partition  coefficients  from  the  slopes  of  the  linear  regression of retention factors as a function of the reciprocal of the phase ratio by means of fundamentalchromatographic  equations. In order to minimize gas?solid and liquid?solid interface contributions to retention,  the  surface  of  the  capillary  inner  wall  was  pretreated  to  guarantee  a  uniform  coat  of  stationaryphase.  The  validity  of  the  proposed  approach  was  first  tested  by  estimating  the  partition  coefficients  of n-alkanes  between  n-pentane  and  n-nonane,  for  which  compounds  data  from  the  literature  were  available.  Then  partition  coefficients  of  sixteen  aliphatic  alcohols  in  squalane  were  determined  at  those  four temperatures.  We  deliberately  chose  these  highly  challenging  systems:  alcohols  in  the  reference  paraffinic  stationary  phase.  These  solutes exhibited  adsorption  in  the  gas?liquid  interface  that  contributed  to retention. The corresponding adsorption constant values were estimated. We fully discuss here the uncertainties  associated  with  each  experimental  measurement  and  how  these  fundamental  determinationscan be performed precisely by circumventing the main drawbacks. The  proposed  strategy  is  reliable  and  much  simpler  than  the  classical  chromatographic  method  employing  packed  columns.