Toksyczność chlorku 1-heksylo-3-metyloimidazoliowego względem wybranych organizmów wodnych

Dokonano oceny potencjału toksykologicznego imidazoliowej cieczy jonowej o nazwie chlorek 1-heksylo-3-metyloimidazoliowy (CHM). Zakres badań ekotoksykologicznych obejmował przeprowadzenie testu toksyczności ostrej z wykorzystaniem skorupiaków słodkowodnych (Thamnocephalus platyurus) i testu toksyczności chronicznej z wykorzystaniem bakterii morskich (Vibrio fischeri). Wartości wskaźników ekotoksykologicznych wyznaczone w poszczególnych testach wyniosły odpowiednio: EC50 2,51 mg/dm3 (THAMNOTOXKIT FTM) i EC50/5min 15,30 mg/dm3 i EC50/15min 14,40 mg/dm3 (MICROTOX® Basic Test 81,9%). Na podstawie uzyskanych wyników związek sklasyfikowano jako toksyczny. W ramach badań dokonano również oceny wpływu korekty odczynu i napowietrzania na redukcję toksyczności roztworu CHM. Doświadczenie przeprowadzono zgodnie z metodyką US EPA/600/6-91/005F. Stwierdzono, że korekta odczynu roztworu CHM do poziomu 3 i 11, a także przeprowadzenie symultanicznego procesu korekty pH do 3 i napowietrzania wpływa na obniżenie toksyczności badanego związku.

Ionic liquids (IL's) are defined as organic salts with low melting point. The reputation of those substances as green solvents (environmental friendly chemicals) is based primarily on their negligible vapor pressure. However, high solubility and stability of those substances in water can cause a serious concern about their toxic potential. Relatively little is still known about the toxicity of these substances as a class, especially when compared to conventional organic solvents. The aim of the study was to investigate the toxicity of imidazolium ionic liquid: 1-heksyl-3-methylimidazolium chloride (CHM) according to selected aquatic organisms: bioluminescent marine bacterium and crustacean. The results showed that CHM caused a harmful effect on tested organisms in the whole range of concentrations used in the tests. The estimated toxic index EC50 obtained 2.51 mg/dm3 according to Thamnocephalus platyurus and EC50/5min 15.30 mg/dm3, EC50/15min 14.40 mg/dm3 according to Vibrio fischeri. The CHM was classified as a toxic substance. Moreover, the toxicity of CHM samples with modified pH values and aeration has been measured. Modifications of CHM samples were based on U.S. EPA Protocol (Toxicity Identification Evaluation). Acute toxicity of each modification have been determined by using the MICROTOX® Basic Test 81.9% standard procedure. The results showed that upgrading pH value to 11 as well as diminishing samples pH to value 3 had an influence on samples' post-reaction toxicity. Both processes, pH correction and aeration, used individually caused a significant decrease of analyzed samples' toxicity expressed as toxic index's EC50 measured after 5 and 15 minutes of exposition. The toxic index values were increased from range 30% (pH 3) up to 100% (pH 11) according to non modified sample. The study showed that pH correction to value 3 connected with simultaneous aeration additionally decrease sample toxicity. The results of the present study has proved that 1-heksyl-3methylimidazolium chloride could be toxic to aquatic organisms and it is necessary to carry out the ecotoxicological risk of ionic liquids by the use of bioassays.