Abstract: A pump device has at least one chamber (22) or conduit containing or provided for containing a liquid, a concentration sensor (24) arranged in the chamber (22) or conduit for detecting a concentration of a substance in the liquid and an evaluation unit (28) connected to the sensor (24). The sensor (24) and the evaluation unit (28) are configured for an electrical impedance measurement. The evaluation unit (28) is configured such that a measurement for detecting the concentration is carried out by use of an electrical signal applied to the sensor (24) having at least one frequency corresponding to or above an upper cut-off frequency (f2) of a frequency range showing a constant electrical impedance (Rm). A method is provided for determining the concentration of a substance inside a liquid.

Abstract: A drug delivery device for delivery of a drug which comprises a mixture of a first substance and a second substance, the device including a first chamber (24) for housing the first substance, a second chamber (30) for housing the second substance and a membrane (28) which on application of a predetermined condition thereto is movable from a first disposition in which it partitions the first and second chambers to prevent mixture of the first and second substances to a second disposition in which it enables the first and second substances to be mixed. In one aspect, the membrane (28) contains a barrier material comprising polychlorotrifluoroethylene or a copolymer thereof, polyvinylidene chloride or a copolymer thereof or a silicon oxide. In another aspect, the first chamber (24) is formed from a polyethylene based polymer.