Design for electrospray ionization-ion mobility spectrometry.

In this study, a new design for electrospray ionization ion mobility spectrometry (ESI-IMS) was developed. This design has two important differences in comparison to the present ESI-IMS systems. First, a few centimeters of the cell comprising the electrospray needle was located outside of the oven used for heating the IMS cell. This modification prevents prespray solvent evaporation problems such as needle clogging and disturbance of the electrospray process. Second, in addition to the drift gas, a counterflow of a heated gas (desolvation gas) was used between the counter electrode and the ion gate to speed up the desolvation process (Hill, H. H., Jr. Anal. Chem. 1998, 70, 4929-4938). This modification increased the solvent evaporation and resulted in decreasing the drift time, increasing the peak intensity and increasing the resolving power (RP) or enhancing the resolution for separation of two adjacent ion peaks. In this work, the ion mobility spectra of different compounds including ethion, malathion, metalaxyl, fenamifos, methylamine, triethylamine, tributhylamine, codeine, and morphine were obtained to confirm enhancing of the resolving power of the ion peaks by using the desolvation gas. Furthermore, the method has also been applied to obtain the figures of merit for ethion as a test compound. The linear dynamic range for ethion was in the range 50-1000 microg/L with a limit of quantification of the 50 microg/L.