Combined (d)SPE-QuEChERS Extraction of Mycotoxins in Mixed Feed Rations and Analysis by High Performance Liquid Chromatography-High-Resolution Mass Spectrometry.

The objective of this work was the development of a methodology capable of simultaneously determine 26 mycotoxins in mixed feed rations collected in 20 dairy farms. A sample preparation methodology based on a combination of (d)SPE and QuEChERS extractions was used. Liquid chromatography-high resolution mass spectrometry was employed for both identification and quantification purposes. To this respect, a powerful workflow based on data-independent acquisition, consisting of fragmenting all precursor ions entering the mass spectrometer in narrow m/z isolation windows (SWATH), was implemented. SWATH data file then contains all the information that would be acquired in a multitude of different experimental approaches in a single all-encompassing dataset. Analytical method performance was evaluated in terms of linearity, repeatability and matrix effect. Relative recoveries were also measured, giving values above 80% for most compounds. Matrix-matched calibration was carried out and enabled reaching the low ng mL-1 level for many mycotoxins. The observed matrix effect, in most cases suppressive, reached even values higher than 60%. The repeatability was also adequate, showing a relative standard deviation lower than 10%. All unified samples analyzed showed co-occurrence of two or more mycotoxins, recurrently zearalenone, fumonisin B1, and ß-zearalenol, with an occurrence frequency ranging from 60% to 90%.

Photodegradation behaviour of multiclass ultraviolet filters in the aquatic environment: Removal strategies and photoproduct identification by liquid chromatography-high resolution mass spectrometry.

Different photodegradation strategies were assessed to remove 21 multiclass organic ultraviolet (UV) filters including benzophenone-, camphor-, and p-aminobenzoic acid- derivatives, methoxycinnamates, and salicylates, among others, from the aquatic environment. Direct photolysis under UVA (λ = 365 nm) and UVC (λ = 254 nm) radiations and advanced oxidation processes (AOPs) based on heterogeneous UVA/TiO2 photocatalysis and the UVC/H2O2 system were applied for the degradation tests. LC-MS/MS and SPME-GC-MS/MS were employed for the monitoring of the target compound degradations. UVC photolysis provided the highest removal efficiency for most of the studied UV filters with degradation yields higher than 90% after 60 min of light exposure in ultrapure water. This radiation was also applied to different real water matrices (river, sea, and swimming-pool water), showing that the degradation yield was dependent on the water matrix, being more difficult the removal of the target compounds in waters with high organic matter content. In an attempt to accelerate the degradation of the studied compounds in this kind of water matrices, the use of a powerful UVC/H2O2 system improvement the reaction kinetics, showing degradation > 90% for most of the studied UV filters. Besides, up to 19 photoproducts could be identified by HRMS.

Simultaneous determination of trace levels of multiclass fungicides in natural waters by solid - phase microextraction - gas chromatography-tandem mass spectrometry.

A solvent-free method based on solid-phase microextraction (SPME) followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) has been developed for the simultaneous determination of eleven fungicides at trace levels in different types of waters. Several experimental SPME parameters such as temperature, fibre coating, and SPME mode, were optimized in order to obtain the highest extraction efficiency. Under the optimal conditions, 100 °C, polyacrilate fibre (PA) and direct-immersion mode, the method was validated showing good linearity, repeatability and reproducibility. Recovery studies were carried out in four different real water matrices and at three concentration levels (20, 200 and 2000 ng L-1), with overall recovery values between 92 and 104% and relative standard deviations (RSD) about 10%. Limits of detection (LODs) at the low ng L-1 were obtained. The method demonstrated its suitability for the determination of fungicides in real water samples using external calibration for quantification purposes as well as for photodegradation studies at low concentration levels.

Photodegradation of multiclass fungicides in the aquatic environment and determination by liquid chromatography-tandem mass spectrometry.

The photodegradation behaviour for nine widespread fungicides (benalaxyl, cyprodinil, dimethomorph, fenhexamide, iprovalicarb, kresoxim-methyl, metalaxyl, myclobutanil and tebuconazole) was evaluated in different types of water. Two different systems, direct UV photolysis and UVC/H2O2 advanced oxidation process (AOP), were applied for the photodegradation tests. For the monitoring of the target compound degradation, a method based on direct injection liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. Several fungicide photodegradation by-products were tentatively identified by high-resolution mass spectrometry (HRMS) as well. For the photolysis studies, the efficiency of different types of radiation, UVC (λ = 254 nm) and UVA (λ = 365 nm), was compared. UVC photolysis provided the highest removal with a complete degradation for fenhexamide and kresoxim-methyl, and percentages between 48 and 78% for the other compounds, excluding iprovalicarb and myclobutanil with removals <35%, after 30 min of irradiation. Besides, the photodegradation tests were performed with different initial concentrations of fungicides, and the efficiency of two photoreactor systems was compared. In all cases, the kinetics followed pseudo-first order, and the half-life times could also be calculated. The addition of H2O2 under UVC light allowed an improvement of the reaction kinetics, especially for the most recalcitrant fungicides, obtaining in all cases removals higher than 82% in less than 6 min. Finally, in order to evaluate the suitability of the proposed systems, both UVC photolysis and UVC/H2O2 system were tested in different real water matrices (wastewater, tap water, swimming pool water and river water), showing that the UVC/H2O2 system had the highest removal efficiency in less than 6 min, for all water samples.