Track membrane mediated electrostatic introduction of cluster ions into TOF mass spectrometer

Glycerol-wetted track membranes (poly(ethylene terephthalate)) are suitable for interfacing between a typical TOF chamber (held at an operational pres sure of less than 10(-6) Torr) and an ambient pressure analyte. Solute conc entration aspects of track membrane mediated electrostatic introduction of negative charged species into TOF mass spectrometer were investigated. Glyc erol solutions of KCl, KBr, NH4I, and Na2S were used. High-field charge ext raction conditions were routinely maintained between the liquid samples (he ld at ambient pressure) and a grounded grid collector. The latter was posit ioned just nearby the vacuum facing side of such membranes. Upon establishi ng a steady-state charge extraction regime, che collector currents were mon itored and recorded at various solute concentration levels. Nonlinear, solu te concentration dependent, collector currents were observed and found to c orrespond to our theoretical treatment. Our findings are accounted for and in support of a special, evaporation limited, mechanism for the track membr ane mediated high-field extraction of cluster ions.