THE DEVELOPMENT OF OPTICAL CHEMICAL SENSORS FOR THE DETECTION OF VOLATILE COMPOUNDS FROM SPOILED HAMS

The vapours from Spanish dry-cured hams are being sampled by an array of different chemical sensors to assess the quality of the hams during the curing process. Some of the sensors analyse the concentration of sulphur-containing compounds in the vapours, as the presence in higher concentrations of these compounds has been identified as one of the f actors indicating the spoilage of hams. The paper describes an optode membrane fabricated by immobilizing tetraoctyrammonium fluorescein mer curic acetate (TOAFMA), tetraoctylammonium hydroxide and tributyl phos phate into a polymeric support (ethyl cellulose) to detect certain sul phur-containing compounds in the vapours from the hams. The fluorescen ce of the TOAFMA is irreversibly quenched by the sulphur-containing co mpounds in the vapours from the hams. It is observed that over a fixed time interval, the vapour from a bad ham causes a greater fluorescenc e quenching effect than that from a good ham and the longer the exposu re time, the greater is the response of the membranes to the ham vapou rs. The compound dimethyl disulphide (DMDS) is used to investigate the response characteristics of the optode membranes. A how rig for produ cing mixtures with accurately known concentrations of DMDS in nitrogen gas is also described. This system could be easily adapted to work wi th any volatile liquid.