Abstract: The invention provides an electrochemical sensor comprising an electrode assembly which comprises at least two electrodes, one of the electrodes comprising a metal species capable of catalysing the oxidation of hydrogen and/or methane. The sensor may be used in the detection and quantification of hydrogen and/or methane in exhaled breath, for example as a means of diagnosing lactose malabsorption or lactose intolerance.

Abstract: There is provided a method of detecting an analyte in a sample, which comprises the steps of contacting the sample with a working electrode in the presence of an electrolyte and determining the electrochemical response of the working electrode to the sample, wherein the working electrode comprises a multi-walled carbon nanotube (MWCNT) and wherein detection takes place in the presence of a species which is capable of forming an intercalation compound with a carbon host material. Electrochemical sensors and compositions suitable for use in said method are also provided.