PREPARATION OF WATER-RESISTANT SUBSTANCES FOR ECOTOXICOLOGICAL TESTING

Sažetak Metode za određivanje toksičnosti kemijskih tvari na vodene organizme, propisane organizacijama kao što su OECD, EU ili ISO odnose se na kemijske supstancije s točnim generičkim opisom, tj. propisuju ispitivanje vodotopljivih, kemijski stabilnih i nehlapljivih tvari. Međutim, ako se te metode primjenjuju za tvari koje ne podliježu navedenim svojstvima (tvari koje su samo djelomično ili slabo topljive u vodi, nestabilne, hlapljive ili kompleksnog sastava), mogu se očekivati teškoće u procjeni toksičnosti. Prema sadašnjim saznanjima najbolja raspoloživa metoda za ispitivanje toksičnosti u vodi slabo topljivih kemijskih tvari je WAF metodologija (Water Accommodated Fraction). WAF predstavlja vodeni medij koji sadrži frakciju supstancije zaostale u vodenom mediju nakon miješanja i odvajanja faza. Predmet naših ispitivanja su maziva teško topljiva u vodi od kojih neka imaju svojstvo intenzivnog prijanjanja uz podlogu i maziva ulja koja s vodom stvaraju emulziju. Prema svom sastavu to su maziva na osnovi sintetičkih estera i biljnih ulja različito ugušćeni sa sapunima ili organofilnim bentonitima. Ispitivana maziva miješana su s deioniziranom vodom i mineralnim medijem pomoću elektromagnetske mješalice i u vremenskom razdoblju od 24-96 sati miješanja praćeni su određeni parametri (koncentracija lipofilnih tvari, totalni organski ugljik i prisutnost organskih kiselina eventualno nastalih hidrolizom estera).Abstract Test methods for assessment toxicity chemical substances to aquatic organisms have been described by various organizations including the OECD, EU or ISO. Those test methods are typically designed for substances with precise generic description and substances, which are readily water soluble, chemically stable and non-volatile. When test methods are applied to substances with different chemical properties (sparingly soluble, unstable or volatile substances or those of a complex composition) it is possible to expect some difficulties in toxicity evaluation. According to present knowledge the best test method for toxicity examination of water-resistant substances is WAF methodology (Water Accommodated Fraction). WAF is an aqueous medium containing only that fraction of a substance which remains in the aqueous phase after mixing and phase separation. The subjects for our examination were water-resistant greases (some of them have very strong adhesive characteristics) and lubricant oils which form emulsion with water. According to their chemical composition there are synthetic based esters and plant oils thickned with soaps and organophylic bentonits. The greases were mixed with deionised water and mineral media on magnetic stirrer and during the time period of 24-96 hours some parameters were defined (concentration of lipophylic substances, total organic carbon and organic acids eventually made by ester hydrolyzis)