Utilization of direct liquid inlet LC/MS in studies of pharmacological and toxicological importance.

Abstract

The temperature of the droplets produced at the tip of the direct liquid inlet liquid chromatography/mass spectrometry (DLI LC/MS) probe decreases to about -70 degrees during the adiabatic evaporation of the droplet in the vacuum of the mass spectrometer. Broadening of peaks eluting from the probe is acceptable, being about 80 microL in volume, as shown by the DLI LC/MS analysis of cortisone, dexamethasone, and corticosterone in both the positive and the negative chemical ionization (PCI and NCI) modes. The minimum amount of sample which can be injected is about 10 ng in the scanning mode and about 100 pg in the selected ion monitoring (SIM) mode as shown by the analysis of bromocriptine and bromocriptinine. Other thermally-labile and/or non-volatile compounds analyzed by this system in the PCI and/or the NCI modes included ergotamine, esculin, sulfamethazine, chloramphenicol, erythromycin, alpha-tocopherol, cocaine, 8-chloro-theophylline, and dicophol. Non-ultraviolet absorbing carbohydrates were also analyzed, including sucrose (NCI), permethylated maltotriose, and partially hydrolyzed, derivitized lichenan and starch. By a flow switching technique, bromocriptine in a Pariodel tablet, ergot alkaloids in a Hydergine drop solution, and bromocriptine and bromocriptinine in whole urine could be analyzed without prior extraction.