Ionic liquids accumulate within Escherichia coli cells and can be detected by Fourier transform infrared (FT-IR) spectroscopy. Harvested cells were incubated with the biocompatible, water-immiscible ionic liquids, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide

][Cl]. The cells were harvested, washed anddried, and their FT-IR spectra were recorded. The ionic liquid spectra could be detected againstthe background spectra of the cells, demonstrating that they were accumulating within the cells.The toxic ionic liquids accumulated more rapidly than the biocompatible ionic liquids. Principalcomponents analysis followed by discriminant function analysis showed that, compared to controlcells, the toxic ionic liquids produced much bigger changes in the FT-IR fingerprint of the cellularchemicals than the biocompatible ionic liquids. Subcellular fractionation, followed by FT-IRanalysis, demonstrated that [P