Quantitative bioanalysis by direct nanoelectrospray infusion coupled to tandem mass spectrometry has been achieved using an automated liquid sampler integrated with an array of microfabricated electrospray nozzles allowing rapid, serial sample introduction (1 min/ sample). Standard curves prepared in human plasma for verapamil (r2 = 0.999) and its metabolite norverapamil (r2 = 0.998) were linear over a range of 2.5-500 ng/ mL. Based on the observed precision and accuracy, a lower limit of quantitation of 5 ng/mL was assigned for both analytes. Sample preparation consisted of protein precipitation with an organic solvent containing the structural analogue gallopamil as an internal standard. Protein precipitation was selected both to maximize throughput and to test the robustness of direct nanoelectrospray infusion. Aliquots of supernatant (10 pL) were transferred to the back plane of the chip using disposable, conductive pipet tips for direct infusion at a flow rate of 300 nL/min. Electrospray ionization occurred from the etched nozzles (30-microm o.d.) on the front of the chip, initiated by a voltage applied to the liquid through the pipet tip. The chip was positioned near the API sampling orifice of a triple quadrupole mass spectrometer, which was operated in selected reaction monitoring mode. Results are presented that document the complete elimination of system carry-over, attributed to lack of a redundant fluid path. This technology offers potential advantages for MS-based screening applications in drug discovery by reducing the time for methods development and sample analysis.
-In 1995 and 1996, a survey for the presence of Phytophthora cinnamomi in cork and holm oak sites in southeastern France was carried out. Twenty-four sites were chosen. Tree decline severity and other characteristics were assessed. Subplots of four trees were more fully investigated: relative soil water content was assessed and Phytophthora isolation was attempted from soil samples.When cortical lesions were observed, isolations were carried out from infected tissues. In six cork oak and one holm oak sites, P. cinnamomi was isolated from soil or trunks. All the different isolates obtained in 1995 were aggressive on cork and holm oaks. However, these species were less susceptible than Castanea sativa and more susceptible than Q. rubra. These results confirm the pathogenicity of P. cinnamomi towards Mediterranean oaks and its possible involvement in the decline process of these species. (
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