Capture of opiates by ionic liquids

Abstract Room temperature ionic liquids (RTILs) are known to provide efficient extraction media for a variety of systems. In particular, their ability to remove low volatility compounds (including opiate drugs) from the surface of human hair was recently demonstrated by this team. Among many tested ILs, some exhibited high extraction efficiencies for the two studied compounds, morphine and 6-monoacetylmorphine, while others have practically zero efficiency. The aim of the present study was to further understand the special affinity of specific combinations cation/anion towards the opiate drugs, through a systematic study of a limited number of ILs: 1-ethyl-3-methylimidazolium acetate, [C₂mim][OAc], 1-butyl-3-methylimidazolium acetate [C₄mim][OAc], 1-hexyl-3-methylimidazolium acetate [C₆mim][OAc], 1-ethanol-3-methylimidazolium tetrafluoroborate, [C₂OHmim][BF₄], 1-ethanol-3-methylimidazolium chloride [C₂OHmim][Cl], and 1-butyl-3-methylimidazolium tetrafluoroborate, [C₄mim][BF₄]. Correlations between the efficiency of drug extraction from hair and the water content, surface tension and polarity of the ionic liquids (ILs) were found. The extraction efficiency increased with the IL's water content, although in a different way for each IL/drug pair. A decrease in the surface tension during the process of drug extraction was detected only for highly efficient ILs. Efficiency was correlated with the polarity parameters defined by Kamlet and Taft: large for ILs of high acidity and low basicity (e.g. [C₂OHmim][BF₄]) and small for liquids with of low acidity and high basicity (e.g. [C₆mim][OAc]).