HPLC OF HEPTACAINE POSITION ISOMERS

Heptacaine (piperidinoethylester of 2-heptyloxyphenylcarbamic acid) an d its position isomers (piperidinoethylester of 3-heptyloxyphenylcarba mic acid) and (piperidinoethylester of 4-heptyloxyphenylcarbamic acid) are studied with respect to their HPLC behaviour. The study of the in fluence of the composition of the mobile phase on the values of the ca pacity factors k' indicated that dependencies of log k' on the content s of methanol (phi) in the mobile phase were linear in the range 80-10 0% for all three compounds. The dependence of capacity factor on pH we re also estimated. It can be concluded that the ratio 1:1 between prot onized and nonprotonized forms is at pH = 6.5. The dependence of the w idth of the peak on pH value were studied, too. If the values of pH we re above 6.5, the peaks were most symmetrical and the width of the pea ks at the baseline had the lowest value. The optimal composition of th e mobile phase was 90% methanol in water and 6.8 g sodium acetate per liter of the mobile phase (C-18 column). This separation system can be used for the determination of all three position isomers.