Identification and subsequent removal of an interference by FAIMS in the bioanalysis of dianicline in animal plasma.

BACKGROUND: The determination of pharmacokinetic parameters requires accurate and reliable bioanalytical methods. Even using highly selective MS/MS, interferences can occur. This paper describes the source of some of these interferences with an example discussed involving the problem of a ketamine interference in a plasma assay. RESULTS: The introduction of field asymmetric waveform ion mobility spectrometry (FAIMS) removed the interference, enhanced signal-to-background and met GLP acceptance criteria. Relative to the non-FAIMS method, assay calibration characteristics were improved. The FAIMS source gave optimal performance following the introduction of a split in order to reduce the inlet flow to approximately 0.4 ml/min. CONCLUSION: The introduction of ion-mobility separation into a bioanalytical LC-MS/MS method can remove unexpected isobaric interferences without the need to redevelop the chromatography.

Host-parasitoid interactions relating to penetration of the whitefly, Bemisia tabaci, by the parasitoid wasp, Eretmocerus mundus.

It has been reported that the aphelinid wasp Eertmocerus mundus parasitizes all four nymphal instars of the sweet potato whitefly, Bemisia tabaci (Biotype B), with 3rd instars being the preferred hosts. The parasitoid lays its egg on the leaf underneath the host nymph. First instars hatch and later penetrate the whitefly. Previous studies have shown that the initiation of parasitoid penetration induces the host to form a cellular capsule around the parasitoid. As described here, females never oviposited once the 4th instar whitefly nymph had initiated adult development. First instar E. mundus larvae were observed under 2nd, 3rd and 4th instar whitefly nymphs, however, penetration did not occur until the whitefly had reached the 4th instar. The non-penetrating E. mundus larva almost always induced permanent developmental arrest in its 4th instar whitefly host and also caused a reduction in whole body host ecdysteroid titers. Therefore, unless there is a peak in molting hormone titer in the area local to penetration, it appears that the induction of capsule formation is not due to an increase in ecdysteroid titer. As the capsule formed around the penetrating parasitoid, host epidermal cells multiplied and became cuboidal and columnar, and relatively thick layers of new cuticle were deposited within the developing capsule, particularly near its ventral opening. The newly formed host cuticle was thinner in the dorsal part of the capsule and appeared to be absent at its apex. These results provide new information regarding the timing and dynamics of parasitoid oviposition and egg hatch as related to larval penetration, parasitoid-induced changes in whitefly development, molting hormone titers and the process of capsule formation.