Fit-for-purpose in veterinary drug residue analysis: development and validation of an LC-MS/MS method for the screening of thirty illicit drugs in bovine urine

A selective and sensitive method for screening 31 analytes (nine corticosteroids, eight β‐agonists, seven anabolic steroids, six promazines and zeranol) in bovine urine was validated according to 2002/657/EC guidelines. Upon optimization of sample treatment conditions, the extraction was performed by diethylether at pH 9, after deconjugation. Extraction yields (R%) proved higher than 70% for 19 analytes, 50<R%<70 for 5 analytes, lower than 50% but reproducible for the remaining six analytes. The analyses were carried out using HPLC‐ESI‐MS/MS. The method sensitivity proved high enough to largely exceed the CCβ requirements of the Italian residue detection plan, ranging from 1 to 3 ng/mL (20 ng/mL for promazines). The present method allowed the simultaneous analysis of most drugs for which the European legislation prescribes official controls. Its practical applicability was verified on 494 real samples as an alternative to the traditional screening protocols based on multiple immunometric analysis, demonstrating high efficiency and comprehensive investigation capacity, allowing epidemiological assessment of the current trends in cattle breeding drug abuse. Among non‐compliant results, nine borderline cases of growth‐promoters illegal treatments, making use of long‐term low‐dosage administrations and typically yielding urine residues below the cut‐off value for immunochemical methods, were detected by using the present LC‐MS/MS method.     

Novel approach for the simultaneous detection of DNA from different fish species based on a nuclear target: quantification potential

The development of DNA-based methods for the identification and quantification of fish in food and feed samples is frequently focused on a specific fish species and/or on the detection of mitochondrial DNA of fish origin. However, a quantitative method for the most common fish species used by the food and feed industry is needed for official control purposes, and such a method should rely on the use of a single-copy nuclear DNA target owing to its more stable copy number in different tissues. In this article, we report on the development of a real-time PCR method based on the use of a nuclear gene as a target for the simultaneous detection of fish DNA from different species and on the evaluation of its quantification potential. The method was tested in 22 different fish species, including those most commonly used by the food and feed industry, and in negative control samples, which included 15 animal species and nine feed ingredients. The results show that the method reported here complies with the requirements concerning specificity and with the criteria required for real-time PCR methods with high sensitivity.     

Determination of glyphosate in groundwater samples using an ultrasensitive immunoassay and confirmation by on-line solid-phase extraction followed by liquid chromatography coupled to tandem mass spectrometry

Despite having been the focus of much attention from the scientific community during recent years, glyphosate is still a challenging compound from an analytical point of view because of its physicochemical properties: relatively low molecular weight, high polarity, high water solubility, low organic solvent solubility, amphoteric behaviour and ease to form metal complexes. Large efforts have been directed towards developing suitable, sensitive and robust methods for the routine analysis of this widely used herbicide. In the present work, a magnetic particle immunoassay (IA) has been evaluated for fast, reliable and accurate part-per-trillion monitoring of glyphosate in water matrixes, in combination with a new analytical method based on solid-phase extraction (SPE), followed by liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS), for the confirmatory analysis of positive samples. The magnetic particle IA has been applied to the analysis of about 140 samples of groundwater from Catalonia (NE Spain) collected during four sampling campaigns. Glyphosate was present above limit of quantification levels in 41% of the samples with concentrations as high as 2.5 μg/L and a mean concentration of 200 ng/L. Good agreement was obtained when comparing the results from IA and on-line SPE-LC-MS/MS analyses. In addition, no false negatives were obtained by the use of the rapid IA. This is one of the few works related to the analysis of glyphosate in real groundwater samples and the presented data confirm that, although it has low mobility in soils, glyphosate is capable of reaching groundwater.     

The converse Lyapunov’s theorem for ODEs of Carathéodory type

The converse problem of Lyapunov stability for systems of ODEs of Caratheodory type is considered. It is proved that if the right hand side of an ODE satisfies only the Osgood condition, the uniform stability of the origin is sufficient to the existence of a locally Lipschitz continuous Lyapunov function. Actually, the uniform stability is equivalent to the robust stability in this case. Moreover, as an auxiliary result, the generalization of the famous Gronwall-Bellman-Bihari inequality is also proved.     

Pupil detection and tracking for analysis of fixational eye micromovements

Even with fixed gaze, the human eye is under steady motion (tremor micosaccades and drifts). Detection of these movements requires of invasive techniques or expensive devices with sophisticated detection methods. In this paper we present a technique for pupil segmentation and contour analysis which will provide valuable information about fixational eye movements. The method is based on fitting an ellipse to the pupil contour. Pupillary hippus, microsaccades and drifts are obtained as well as cyclotorsional movements. The method is simple and the experimental requirements are easily available since just a biomicroscope and a digital videocamera are required.     

Femtosecond pulsed laser deposition of nanostructured TiO2 films

Nanostructured deposits of TiO₂ were grown on Si (1 0 0) substrates by laser ablating a TiO₂ sintered target in vacuum or in oxygen using a Ti:sapphire laser delivering 80 fs pulses. The effect of the laser irradiation wavelength on the obtained nanostructures, was investigated using 800, 400 and 266 nm at different substrate temperatures and pressures of oxygen. The composition of the deposits was characterized using X-ray photoelectron spectroscopy (XPS) and the surface morphology was studied by environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM). Deposits are absent of microscopic droplets in all conditions explored. The best deposits, constituted by nanoparticles of an average diameter of 30 nm with a narrow size distribution, were obtained at the shorter laser wavelength of 266 nm under vacuum at substrate room temperature.     

Looking for the optimal DTI acquisition scheme given a maximum scan time: are more b-values a waste of time?

In this study we used simulated data to investigate how valuable the use of multiple b-values is, in terms of improving the accuracy and reproducibility of Diffusion Tensor Imaging (DTI) results. Our results show that the systematic bias of the estimated scalar diffusion parameters [apparent diffusion coefficient and fractional anisotropy (FA)] - due to the Rician distribution of magnetic resonance noise - can be minimized by increasing the number of b-values and not by increasing the number of sampling directions. In addition, the use of more than one b-value accounts better for the wide range of diffusivities found in the human brain by bringing closer together the FA estimates for fibres with different mean diffusivities. It is also shown that while for tractography studies we should use as many sampling directions as allowed by scan time limitations, for follow-up, intersubject or multicenter studies, the use of more than one b-value will improve the accuracy of the scalar diffusion parameters, as long as the minimum number of directions required for robust estimation of each parameter is still used.     

On the Existence of Traveling Waves in the 3D Boussinesq System

We extend earlier work on traveling waves in premixed flames in a gravitationally stratified medium, subject to the Boussinesq approximation. For three-dimensional channels not aligned with the gravity direction and under the Dirichlet boundary conditions in the fluid velocity, it is shown that a non-planar traveling wave, corresponding to a non-zero reaction, exists, under an explicit condition relating the geometry of the crossection of the channel to the magnitude of the Prandtl and Rayleigh numbers, or when the advection term in the flow equations is neglected.     

Cu(II)-imprinted styrene-divinylbenzene beads as a new sorbent for flow injection-flame atomic absorption determination of copper

The paper reports preparation and analytical features of a new Cu(II)-imprinted polymer, based on salen-OMe ligand 2,2′-[ethane-1,2-diylbis(nitrilo(E)methylylidene)]bis(6-allyl-4-methoxyphenol) and styrene-divinylbenzene matrix, as well as its application to on-line preconcentration and flame atomic absorption determination of copper. Sorbent beads (average diameter of 60-80 µm) were obtained using suspension polymerization technique and employed as a column filling. Copper sorption was the most effective at pH 6.8, whereas the highest elution effectiveness was observed when 0.5% HNO₃ was applied. The sorbent exhibited good long-term stability and acid resistance. Enrichment factor (EF) of 12 was found for 60 s loading time and loading flow rate of 4 mL min^− 1. EF value may be further increased by expanding the loading time and/or flow rate. Batch sorbent capacity in optimal pH conditions was found to be 0.16 mmol g^− 1 (9.55 mg g^− 1) of a dry polymer. Calcium(II) turned out to be the only significant interferent. Cadmium(II), silver(I), nickel(II), zinc(II) in concentrations lower than about 1 mg L^− 1 did not disturb copper(II) preconcentration. Different calibration methods such as: set of standards method (SSM), standard addition method (SAM) and combinatory calibration method (CCM) were employed for copper(II) determination in tap water, spring mineral water and certified reference material. Analysis of EU-H-3 reference material confirmed good accuracy of the proposed method. Relative standard deviation (RSD) was 3.2 for standard addition method and 2.8% for set of standard calibration method. Detection limit for sample consumption 16 mL was 1.03 and 1.07 µgL^-1 respectively.