Method for the quantitative determination of vitamins, amino acids, or other substances necessary for life, in a substance mixture, whereby in the culture container, the cavities of a microtitration plate, in each case a predetermined number of vital cells of a suitable microorganism are prepared in a permanent manner. For this purpose, the cells are shock frozen at −80° C. and then freeze dried in a freezing solution containing 200 to 500 mM trehalose/sucrose. The freezing solution is preferably the test medium. The culture containers are preferably the wells of a microtitration plate.