CO2 as a solvent for natural pesticides

U ovom su radu procijenjene topljivosti prirodnih pesticida – složenih organskih spojeva (triterpenoidi azadirahtin, nimbin i salanin dobiveni iz nima te piretrini piretrin I i II, cinerin I i II i jasmolin I i II dobiveni iz cvjetova različitih vrsti krizantema) – u smjesama nadkritičnog CO2 i etanola. Potrebni parametri za procjenu topljivosti dobiveni su raspoloživim empirijskim metodama, odnosno Peng-Robinsonovom jednadžbom stanja. Ravnotežni tlakovi sublimacije procijenjeni različitim metodama međusobno nisu slagali i za po nekoliko redova veličine, što je uvelike ograničavalo pouzdanost procjena topljivosti. Proračun topljivosti stoga je ograničen samo na nimbin – rezultati su pokazali da se najveća topljivost može očekivati pri nižim temperaturama i srednjim tlakovima, te da povećanje udjela etanola u smjesi s nadkritičnim CO2 povećava njegovu topljivost.In this paper the solubilities of natural pesticides – complex organic compounds (triterpenoids azadirachtin, nimbin and salanin derived from neem seeds and pyrethrins pyrethrin I and II, cinnerin I and II and jasmolin I and II obtained from the flowers of various chrysanthemum species) – in the mixtures of supercritical CO2 and ethanol were estimated. The required parameters for assessing the solubility were obtained by available empirical methods as well as with the Peng-Robinson equation of state. The sublimation pressures of pure solids estimated with different methods were not coherent and differed by several orders of magnitude, which greatly limited the reliability of obtained estimates. Therefore only the solubility of nimbin was calculated – the results showed that the largest solubility may be expected at lower temperatures and medium pressures; the increase of ethanol content in the mixture with CO2 was found to increase the solubility