Interactions between yeasts, fungicides and apple fruit russeting.

The effect of inoculations with yeasts occurring on apple surfaces and fungicide treatments on the russeting of Elstar apples was studied. Captan, dithianon and a water treatment were implemented to study the interaction between the fungicides, the inoculated yeast species and Aureobasidium pullulans, and the development of russet. All yeast inoculations aggravated russet, but Rhodotorula glutinis, Sporidiobolus pararoseus and A. pullulans did so to a greater extent than the other species. Both captan and dithianon significantly reduced russeting. Denaturing gradient gel electrophoresis analysis showed that inoculations with R. glutinis and S. pararoseus seemed to suppress other yeast species present on the apple surface.

Determination of 17beta-estradiol in bovine plasma: development of a highly sensitive technique by ion trap gas chromatography-tandem mass spectrometry using negative chemical ionization.

A novel approach to the determination of 17beta-estradiol in bovine plasma is presented. The observed enhanced sensitivity is gained by the application of tandem mass spectrometry (MS) fragmentation to a stable, well characterized negative ion produced by chemical ionization (methane as reagent gas). A specific derivatizing reactant is employed (pentafluorobenzyl bromide), combined with bis-trimethylsilyltrifluoroacetamide, to favor the formation of a diagnostic precursor negative ion. Plasma samples are purified through a C18 solid phase extraction column and derivatized before gas chromatography-MS analysis. The accuracy and the precision of the method, tested over a set of spiked samples, were satisfactory. The limit of detection was found to be 5 pg ml(-1) and the limit of quantification was fixed at 20 pg ml(-1). The fragmentation pattern is fully explained and the method is applicable for the official analysis of bovine plasma for the detection of 17beta-estradiol according to the European criteria 256/93 and to the draft SANCO/1805/2000 rev. 3. The quantification of incurred positive samples was performed according to the proposed procedure and compared with the results obtained by standardized radio immuno assay; the estimated concentrations were significantly similar.