Effect of column temperature and nitrogen flow rate on the separation of cis-permethrinic acid isomers on a (2,3,6-tri-O-methyl)-beta-cyclodextrin coated capillary column.

The separation efficiency of a capillary column coated with (2,3,6-tri-O-methyl)-beta-cyclodextrin was determined at the temperature and flow rate ranges of 80-120 degrees C and 0.3-1.5 mL/min respectively using (+) and (-) cis-permethrinic acid methylesters as test compounds. The dependence of the retention differences, sum of peak widths and separation factor on the temperature and flow rate was calculated with step regression analysis. The column exhibited acceptable isomer separation capacity at each temperature and flow rate proving the excellent separation power of the cyclodextrin coating. The differences between the retention times of isomers depended on the logarithm and on the reciprocal value of temperature, the effect of flow rate was negligible. The sum of their peak widths depended reciprocally on the temperature and logarithmically on the flow rate, the impact of temperature being higher than that of flow rate. The significant impact of the reciprocal value of temperature can be explained by the inclusion complex formation between cyclodextrin and cis-permethrinic acid methylester isomers. The resolution depended on the square of column temperature and flow rate, indicating local optimums at each temperature and flow rate.