MS MS ANALYSES OF ECDYSTEROIDS IN DEVELOPING EGGS OF DYSDERCUS-FASCIATUS/

Several techniques are now available for analysing ecdysteroids. In th is paper we describe a new rapid technique to obtain chemical characte rization of the ecdysteroids. MS/MS is a convenient technique that can be used for mixtures or partly purified compounds. Conditions of anal yses are described to allow the detection of small amounts (50 ng) of ecdysteroids in partly purified biological samples. First, using stand ard solutions, we optimized the conditions to obtain the pseudo-molecu lar ion (MH+) with the highest relative intensity (100%). Such conditi ons were obtained using DCI/NH3 with a pressure of 1.2 10(-4) torr. Th is ion was selected through the first analyser and introduced into the collision cell. After collision with neutral atoms of argon in the co llision cell, it was dissociated to give daughter ions. The residual p arent ion and the daughter ions were then analysed by the second analy ser. Collision activated dissociation of the parent ion generates the daughter ions or MS/MS spectrum of the molecule. This technique gives a good characterization of the molecules to be analysed. Using the con ditions determined with standards, we developed the analysis from part ly purified biological extracts. Sample from pooled HPLC fractions was introduced into the ionization chamber where all the molecules were i onized. From these ions, we selected an ion corresponding to a known e cdysteroid (RT of HPLC fractions). This ion was introduced into the co llision cell to produce daughter ions. By comparison with the daughter ion spectrum of a standard recorded under the same conditions we can confirm the nature of the ecdysteroid detected. We improved this techn ique for analysing ecdysteroids contained in Dysdercus fasciatus eggs. Both makisterone A and makisterone C were detected and characterized through diagnostic daughter ions in the eggs.