COMPARISON OF AROMATIC SULFONIC-ACIDS IN REVERSED-PHASE ION-PAIR LIQUID-CHROMATOGRAPHY WITH DIFFERENT ORGANIC MODIFIER AND ION-PAIR REAGENTCONCENTRATION

The capacity factors of 15 aromatic sulphonic acids in reversed-phase ion-pair liquid chromatography (RP-IPC) with acetonitrile / water and methanol / water containing ion-pair reagent tetrabutylammonium iodide were measured, the linear regression between the 1nk/ values and meth anol, acetonitrile concentrations according to equation 1nk(') = a+Cc( b) was carried out, good linear relationships of the 1nk(') values, th e parameters a and C with acetonitrile as organic modifier vs. those w ith methanol as organic modifier were obtained, which mean that there is no significant difference in acetonitrile and methanol affecting th e selectivity, the acetonitrile has a stronger eluent strength than me thanol. The combined effect of organic modifier and ion-pair reagent c oncentration on retention values can be expressed by the equation 1nk( ') = A+B In c(p) +Cc(b), in a suitable range of ion-pair reagent conce ntration. A critical value the positive effect of ion-pair reagent con centration on retention is equal to the negative effect of organic mod ifier concentration on retention has been obtained.