Determination of nitrofurans residues in animal feeds by flow injection chemiluminescence procedure

A simple flow injection chemiluminescence (FI-CL) method was developed for the rapid and sensitive determination of nitrofurans, including furazolidone, nitrofurantoin and nitrofurazone, in animal feeds based on its chemiluminescence induced by potassium permanganate in sulphuric acid medium. The method involves the injection of nitrofuran samples or standards into H₂SO₄ carrier stream, which then merges at a T-piece with a reagent stream consisting of KMnO₄ in the H₂SO₄ carrier solution. The elicited chemiluminescence intensity of the resulting reaction mixture was measured by photomultiplier tube operated at a voltage of 950 V. Optimum CL signals were given using 2.5 × 10⁻⁵ mol L⁻¹ potassium permanganate in 0.1 mol L⁻¹ sulphuric acid as an oxidant stream and a carrier stream of 0.1 mol L⁻¹ sulphuric acid with a total flow rate of 7.0 mL min⁻¹. Results detailing the optimisation of the analytical signal, calibration, and common interferences of animal feeds were also discussed. The proposed FI-CL method was successfully applied to the determination of nitrofurans in animal feeds, with excellent recoveries, as the determination is free from interference. The method validation has been compared versus HPLC method for animal feed samples.     

Critical effect of oxygen on aroma compound production by Proteus vulgaris

Aroma compound production by Proteus vulgaris was studied in a liquid medium under two culture conditions, static or shaken. By using a dynamic headspace technique coupled with gas chromatography–mass spectrometry, 30 volatile components, aldehydes, alcohols, esters, ketones, sulphur compounds and other miscellaneous compounds were identified. P. vulgaris produced a variety of volatile compounds in different amounts, depending on its culture condition. Sensory analysis has shown that the aroma characteristics of each culture condition were clearly differently perceived. The volatile composition was in agreement with the aroma perception. The culture medium obtained without agitation was characterised by a sulphur/rotten egg note and by a high level of H₂S. The culture medium obtained with agitation was characterised by fruity/fresh and cheese notes and by a high level of alcohols and volatile sulphur compounds. Thus, P. vulgaris could be a useful microorganism to produce various and numerous natural aroma compounds, depending on the culture conditions during fermentation.