Factors influencing the determination of analyte ion surface partitioning coefficients in electrosprayed droplets

The observed response in mass spectrometry utilizing electrospray as a samp le introduction technique can be affected by a number of factors. In this s tudy a series of two-electrolyte systems was investigated and the mass spec trometric responses were modeled by the use of droplet surface partitioning coefficients and instrumental response factors according to a recently rep orted method (Sjoberg et al., Anal. Churn. 2001, 73, 23-28). The partitioni ng coefficient and the instrumental response factor were found to be affect ed by the chosen experimental conditions. Experimental parameters that were investigated include spray position relative to the orifice, spray potenti al, nebulizer and curtain gas flow rates, ionic strength, and organic conte nt of the sprayed solution. The time history of the generated droplets turn ed out to be of importance to both the partitioning coefficients and the in strumental response factor. For example, a general increase in the surface partitioning coefficients for the tetrapentylammonium ion was initially obs erved when the spray was aiming closer to the sampling orifice. Furthermore , it was shown with a small amount of deuterium labeled electrolyte that th e total ionic strength and not just the electrolyte concentration influence the instrumental response factor. (C) 2001 American Society for Mass Spect rometry.