MODELING AND OPTIMIZATION OF THE SEPARATION OF STEROIDS ELUTED WITH AMICELLAR MOBILE-PHASE OF SODIUM DODECYL-SULFATE CONTAINING ACETONITRILE

The equation 1/k' = c(0) + c(1) mu + c(2) phi + c(3) mu phi + C-4 phi( 2) (mu is the surfactant concentration and phi is the amount of modifi er) proved to be satisfactory in the description of the retention of s everal steroids (boldenone, dydrogesterone, medroxyprogesterone, metha ndrostenolone, methyltesrosterone, medroxyprogesterone acetate and tes tosterone) and two diuretics (amiloride and chlorthalidone) when elute d with micellar mobile phases containing sodium dodecyl sulphate (SDS) and acetonitrile. Modelling of the retention and an adequate selectio n of the experimental design allowed the rapid and reliable optimizati on of the separation of a mixture of steroids. The retention of steroi ds was moderately affected by an increase in the concentration of the surfactant. The elution strength of acetonitrile was relatively low an d thus, a large amount of the modifier was required to obtain adequate retention times. However, the small variation in the resolution achie ved in mobile phases of increasing eluent strength permitted the separ ation of the low (boldenone, medroxyprogesterone, methyltestosterone, medroxyprogesterone acetate) from the high (progesterone, clostebol ac etate and testosterone propionate) retained steroids in the same chrom atogram in less than 40 min.