Carbon film electrodes have been characterised in the room temperature ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethane)sulfonimide (BmimNTF 2 ), 1-butyl-1-methylpyrrolidinium bis(trifluoromethane)sulfonimide, (BpyrNTF 2 ) and 1-butyl-3-methylimidazolium nitrate (BmimNO 3 ), by cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical behaviour of the ionic liquids depended on both cation and anion of these electrolytes. Oxygen reduction is clearly visible at carbon film electrodes -after oxygen removal the potential window was wider, that of BpyrNTF 2 being the widest. These room temperature ionic liquids were used in the electrochemical investigation of two ferrocene derivatives, benzoyl-and acetyl-ferrocene, that are both insoluble in water and cannot be investigated in aqueous solutions. They were also applied in the investigation of two sensor and biosensor mediators, copper hexacyanoferrate and poly(neutral red), with a view to using ionic liquids as electrolytes in electrochemical sensing and biosensing systems.

Two room temperature ionic liquids, 1-butyl-3-methylimidazolium bistriflimide and 1-butyl-3-methylimidazolium nitrate, were employed for enzyme immobilization in a new sol-gel matrix and, for the first time, were successfully applied as electrolyte carriers in a biosensing system. The new sol-gel matrix, based on 3-aminopropyltrimethoxysilane and 1-butyl-3-methylimidazolium bistriflimide mixtures, did not crack even after several weeks when kept dry, and exhibited similar analytical properties to aqueous sol-gel based glucose biosensors. The linear range was up to 1.1 mM of glucose, sensitivity was 62 nA mM À1 and the limit of detection was 28.8 mM. The optimum ionic liquid electrolyte carrier was found to be 1-butyl-3-methylimidazolium nitrate, where the biosensor was made by electrodeposition of the redox mediator, poly(neutral red), and the enzyme was immobilized by cross-linking with glutaraldehyde. The results showed that application of room temperature ionic liquids to biosensors is very promising and can be further exploited.

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a b s t r a c tBiosensors have been prepared by modification of glassy carbon electrodes with functionalised multiwalled carbon nanotubes (MWCNT) dispersed in the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethane)sulfonimide (BmimNTF 2 ) and with lipase cross-linked with glutaraldehyde. The biosensor was applied to the determination of olive oil triglycerides by cyclic voltammetry. A phosphate buffer (pH 7.0)/BmimNO 3 mixture is a better electrolyte than aqueous buffer alone. The response signal in the buffer-BmimNO 3 mixture was found to increase with the number of cycles until a constant current was achieved. The calibration curve obtained exhibited a sigmoid shape and a four-parameter model was used to fit the data which gave a limit of detection of 0.11 lg mL À1 . Close inspection of such calibration curves showed two distinct linear regions indicating changes in the mechanism of the electrochemical response. Overall, the oxidative analytical response was found to be due to phenolic compounds present in the olive oil, released in the presence of lipase, rather than due to triglycerides per se. It was also found that there were no interferences from either cholesterol or glycerol. A possible mechanism of olive oil determination at a MWCNT-BmimNTF 2 /Lip biosensor is proposed.