Gas phase electrochemical detection of single latex particles

In this study we describe zero current potentiometric measurements in a gaseous flame electrolyte, for the detection of single latex particles. Combustion of polystyrene latex particles when added to a premixed hydrogen/oxygen/nitrogen flame, results in an increase in charged species relative to the surrounding hydrogen flame. As a consequence of this increase in ionic concentration over background, short-lived potential difference transients were measured between two platinum indicator electrodes placed in a two-compartment flame electrochemical cell (described in Electrochem. Commun., 2001, 3, 675-681). The frequency of the transient events was dependent on the number density of latex particles in solution. It is proposed that each short-lived transient event corresponds to the combustion of single latex particles in a flame. A potential difference maximum of 0.56 V when 3.0 microm diameter particles were added to the flame was measured. Also it was shown that it is possible to detect 0.3 microm diameter latex particles using the same technique. It is postulated that the physical basis of the potential difference is due to the establishment of diffusion/junction potential due to the increase in ionisation from polystyrene combustion at the surface of one indicator electrode. This methodology may be applied to the detection of particulates composed of ionisable species (organic or inorganic) in gaseous environment such as bacteria, viruses, pollen grains and dust.