Trace analysis of parabens preservatives in drinking water treatment sludge, treated, and mineral water samples.

Parabens have been widely used as antimicrobial agents, mainly in food products, pharmaceuticals, and cosmetics. Although they are known as safe preservatives, they also cause some harm to human health, which has been discussed lately. Therefore, the aim of this study was to evaluate the occurrence of nine parabens (including isomers) in mineral and drinking waters, besides in drinking water treatment sludge (DWTS) samples with determination by liquid chromatography tandem mass spectrometry (LC-MS/MS). Both methods solid phase extraction (SPE) and QuEChERS were validated. Calibration curves showed a correlation coefficient of 0.99 for all compounds. LOQ values ranged from 0.04 to 4 µg L-1 in aqueous matrices and from 5 to 500 ng g-1 in DWTS. Recoveries between 70 and 115% were reached with RSD below 20% for all compounds in SPE whereas recoveries between 62 and 119% were found with RSD below 20% for almost all compounds in QuEChERS. Matrix effect had low values (< 20%); it was only above 20% for methylparaben in the SPE and for pentylparaben in the QuEChERS. Using a quick and simple extraction procedures with SPE, QuEChERS, and LC-MS/MS analyses, these methods proved to be selective and sensitive. They were successfully applied to real samples (treated water, mineral water, and sludge), and methylparaben was detected at concentration levels below 0.242 µg L-1 in mineral and treated water samples and 10 ng g-1 in DWTS samples.

Chitosan from shrimp shells: A renewable sorbent applied to the clean-up step of the QuEChERS method in order to determine multi-residues of veterinary drugs in different types of milk.

Clean extracts are essential in LC-MS/MS, since the matrix effect can interfere in the analysis. Alternative materials which can be used as sorbents, such as chitosan in the clean-up step, are cheap and green options. In this study, chitosan from shrimp shell waste was evaluated as a sorbent in the QuEChERS method in order to determine multi-residues of veterinary drugs in different types of milk, i. e., fatty matrices. After optimization, the method showed correlation coefficients above 0.99, LOQs ranged between 1 and 50µgkg-1 and recoveries ranged between 62 and 125%, with RSD<20% for all veterinary drugs in all types of milk under study. The clean-up step which employed chitosan proved to be effective, since it reduced both the matrix effect (from values between -40 and -10% to values from -10 to +10%) and the extract turbidity (up to 95%). When the proposed method was applied to different milk samples, residues of albendazole (49µgkg-1), sulfamethazine (