Graphene oxide-based degradation of metaldehyde: Effective oxidation through a modified Fenton’s process

A modified graphene oxide-based Fenton’s reaction has been investigated for the degradation of a challenging emerging contaminant which is not effectively removed in conventional water treatment. Metaldehyde, used as the challenge molecule in this study, is a common molluscicide that (like many highly soluble contaminants) has frequently breached European regulatory limits in surface waters. The new method involves graphene with higher hydrophilic characteristics (single-layer graphene oxide, SLGO) as a system that participates in a redox reaction with hydrogen peroxide and which can potentially stabilize theOH generated, which subsequently breaks down organic contaminants. The modified Fenton’s reaction has shown to be effective in degrading metaldehyde in natural waters (>92% removal), even at high contaminant concentrations (50mgmetaldehyde/L) and in the presence of high background organic matter and dissolved salts. The reaction is relatively pH insensitive. SLGO maintained its catalytic performance over 3 treatment cycles when immobilized. Its performance gradually decreased over time, reaching around 50% of starting performance on the 10th treatment cycle. X-ray photoelectron spectroscopy (XPS) analysis of modifications caused in SLGO by the oxidizing treatment indicated that the oxidation of CC sp2to carbonyl groups may be the cause of the decrease in performance. The proposed modified Fenton’s process has the potential to substitute traditional Fenton’s treatment although regeneration of the nanocarbon is required for its prolonged use

Preparation of a beef-extract as a laboratory reference material for the determination of heterocyclic amines.

The present paper describes the preparation of a suitable laboratory reference material (LRM) to validate analytical methods for the determination of heterocyclic amines (HAs) in foods. Three different lots of reference material were prepared using a beef extract which was contaminated with a well-known quantity of amines at different levels ranging from 10 to 75 ng/g. These materials were then lyophilised under determined conditions and, after grinding and sieving, homogenised and, finally, bottled and labelled. Homogeneity and stability studies were performed and no statistical differences were observed in the analysis of variances for within- and between-bottle results, thus demonstrating the homogeneity of the material. Stability at different storage temperatures (- 18, +4 +25 and +40 degreesC) and times (1, 2, 3 and 6 months) was also tested. Therefore, the material can be considered homogeneous and stable and can be proposed for use in inter-comparison exercises for the determination of HAs