Simple and rapid formic acid sample treatment for the isolation of HgSe nanoparticles from animal tissues.

The present work explores for the first time the potential of formic acid on the extraction of tiemannite (HgSe) nanoparticles from seabird tissues, in particular giant petrels. Mercury (Hg) is considered one of the top ten chemicals of major public health concern. However, the fate and metabolic pathways of Hg in living organisms remain unknown. Methylmercury (MeHg), largely produced by microbial activity in the aquatic ecosystems is biomagnified in the trophic web. HgSe is considered the end-product of MeHg demethylation in biota and an increasing number of studies focuses on the characterization of this solid compound to understand its biomineralization. In this study, a conventional enzymatic treatment is compared with a simpler and environmentally friendly extraction by using formic acid (5 mL of = 50 % formic acid) as exclusive reagent. The analyses by spICP-MS of the resulting extracts from a variety of seabird biological tissues (liver, kidneys, brain, muscle) reveal comparable results by both extraction approaches in terms of nanoparticles stability and extraction efficiency. Therefore, the results included in this work demonstrate the good performance of employing organic acid as simple, cost effective and green procedure to extract HgSe nanoparticles from animal tissues. Moreover, an alternative consisting of a classical enzymatic procedure but with ultrasonic assistance reducing the extraction time from 12 h to 2 min is also described for the first time. The sample processing methodologies developed, combined with spICP-MS, have emerged as powerful tools for the rapid screening and quantification of HgSe nanoparticles in animal tissues. Finally, this combination allowed us to identify the possible occurrence of Cd particles and As particles associated with HgSe NPs in seabirds.

Efectos de un programa autónomo de locomoción refleja adaptado a la recuperación de la mano del paciente neurológico crónico adulto. Estudio piloto pretest-postest / Effects of the autonomous application of an adapted reflex locomotion program on the neurological hand of the chronic adult patient. Pretest–posttest pilot trial

Antecedentes: La recuperación de la función de la mano es uno de los aspectos más complejos para los pacientes que han sufrido las secuelas de un daño neurológico. Objetivo: Evaluar los efectos a corto plazo sobre el miembro superior afectado de la realización autónoma de un ejercicio de locomoción refleja adaptado a la sedestación en el paciente neurológico crónico. Método: Diseño pretest-postest. Participaron 13 pacientes (8 mujeres) con edad media de 47,61 (DE 16,03). Posibilidad de pinza y abducción de hombro mínima de 30°. Se realizaron 3sesiones en 2semanas consecutivas, entrenando al paciente para realizar el ejercicio en su casa sin ayuda. Se valora el efecto de la terapia antes y después de la primera sesión, a las 2semanas y 3meses después. Se midieron la prensión con el test de Sollerman y la velocidad y la función global del brazo afecto con el Box-Block test. Resultados: En la 1.ª sesión en Box-Block pasó de 18,6 a 22,6 cubos (p <0,002). Resultados mantenidos en 2.ª y 3.ª evaluación. En el Sollerman test, pasó de una media de 41,4 a 46,9 puntos (p <0,003) en 1.ª evaluación y 47,15 puntos en 2.ª (p <0,002). A los 3meses se mantienen los efectos (0,005). Conclusiones: La aplicación de un programa de locomoción refleja adaptado a la sedestación en pacientes con secuelas en el miembro superior, ofrece la posibilidad al paciente de autogestionar la terapia aumentando su intensidad. Se mejoran con ello la función y la movilidad del miembro superior a corto plazo. (AU)

Background: The recovery of hand function is one of the most complex aspects for patients who have suffered the sequelae of neurological damage. Objective: To evaluate the short-term effects on the affected upper limb of the autonomous performance of a reflex locomotion exercise adapted to sitting in chronic neurological patients. Method: Pretest–postest design. Thirteen patients (8 women) participated with a mean age of 47.61 (SD 16.03). Possibility of clamping and minimum shoulder abduction of 30°. Three sessions were held in 2consecutive weeks, training the patient to perform the exercise at home without assistance. The effect of the therapy is assessed before and after the first session, at 2weeks and 3months later. Grip was measured with the Sollerman test, and the speed and global function of the affected arm with the Box–Block test. Results: In the 1st session in Box–Block it went from 18.6 to 22.6 cubes (P<.002). Results maintained in 2nd and 3rd evaluation. In the Sollerman test, it went from an average of 41.4–46.9 pts. (p<.003) in 1st evaluation, and 47.15 pts. in 2nd (P<0.002). After 3months the effects are maintained (.005). Conclusions: The application of a reflex locomotion program adapted to sitting in patients with sequelae in the upper limb, offers the patient the possibility of self-managing therapy by increasing its intensity. This improves the function and mobility of the upper limb in the short term. (AU)

Comparison of sample preparation strategies for target analysis of total thyroid hormones levels in serum by liquid chromatography-quadrupole time-of-flight-mass spectrometry.

This paper describes a novel method based on liquid chromatography quadrupole time-of-flight-mass spectrometry (LC-QTOF-MS) for target analysis of total THs in serum. Several sample preparation strategies have been evaluated to reduce matrix effect (namely, HybridSPE cartridges, supported liquid extraction, SLE and solid phase extraction, SPE). Deproteinization and further clean-up with mixed-mode SPE was selected as the best strategy for sample preparation, since achieved the cleanest extracts and reduced ionization suppression effects (between -11 and -24%). Method validation was performed by the analysis of control human serum samples. Criteria for confirming THs identity in serum extracts were based on retention times, accurate masses, isotopic pattern and MS/MS fragmentation pattern. Moreover, the quantitation capabilities of the LC-QTOF-MS method were also evaluated in terms of linearity, precision, accuracy and sensitivity by the application of matrix-matched calibration. Additionally, the developed LC-QTOF-MS method successfully provides qualitative information on endogenous components responsible of ion suppression (e.g. lysophosphatidylcholines), via post acquisition data analysis. This demonstrates the significant advantage of using LC-QTOF-MS, as it allows retrospective querying of the acquired data without the need of re-injecting/re-processing the samples.

Bioaccumulation and transformation of methylmercury and selenite using zebrafish (Danio Rerio) larvae as a model.

Bioaccumulation and possible transformation of methylmercury and selenite has been checked on a 72 h-cycle of bioaccumulation and depuration using larvae from zebrafish. The larvae were exposed to methylmercury and selenite at concentrations of 1% and 0.1% of their LC(50) values. Quantitative extraction of methylmercury and selenite from exposed larvae was achieved by using ultrasonic probe-assisted extraction (USP), thus reducing extraction time and solvent consumption. Extracted species collected at different exposure times were characterized and quantified by liquid chromatography coupled to ICP-MS. Bioconcentration factors (BCFs) were estimated by two procedures: (i) as the ratio of the contaminant concentration in larvae and exposure media (BCF(48 h)) and (ii) fitting contaminant concentration in larvae to bioaccumulation models that describe uptake and depuration processes (BCF(k)). The BCFs obtained for methylmercury were 5000 and 2333 for larvae exposed to 1 µg L(-1) and 10 µg L(-1), respectively; while for selenite the BCF was 74 for larvae exposed to 10 µg L(-1). The good correlation between the BCFs found and those previously reported in the literature shows the proposed method as a good and promising alternative to the OECD Bioconcentration Test 305. Actually, the use of zebrafish larvae reduces the bioaccumulation test time from forty two (OECD Bioconcentration Test 305) to three days. In addition, potential biotransformation of both methylmercury and selenite was evaluated by LC-ICP-MS. For this purpose, a method for species extraction in small size samples by using ultrasonic probe sonication was developed.

The capillary cold trap as a suitable instrument for mercury speciation by volatilization, cryogenic trapping, and gas chromatography coupled with atomic absorption spectrometry.

An innovative accessory for speciation analysis has been developed. The system is based on the combination of cryogenic trapping and gas chromatographic separation, carried out within the same capillary. The instrument, hyphenating derivatization, gas-phase extraction, preconcentration, and analyte separation, is semiautomated, and all operational parameters are adjustable via an in-house-developed control unit, which regulates the selected parameters throughout the analysis process. Species detection was carried out by atomic absorption spectrometry. The detection limits achieved were 33, 39, and 71 ng L(-1) for dimethylmercury, methylmercury, and inorganic mercury, respectively. A complete chromatogram could be obtained within three minutes, resulting in the duration of one whole analysis cycle of about 15 min. The proposed method was applied to mercury speciation in freeze-dried tuna fish powder after microwave-assisted extraction, finding that mercury is present at 80% as methylmercury and about 20% as inorganic mercury, in this kind of biological material.

Feasibility study prior to the certification of trace elements in urban and industrial wastewater reference materials.

Reliable results for the determination of trace elements in urban and industrial wastewaters are of paramount importance for both checking the performance of sewage treatment and for detecting possible urban or industrial contamination sources. The quality control of measurements should in principle rely on external tools such as certified reference materials (CRM), which should represent, as closely as possible, the matrix of samples currently analysed, e.g., in the frame of environmental monitoring. To date, however, no CRM representatives of wastewater composition are available, which limits the possibility for control laboratories to check their QC externally. To fill this gap, the European Commission's Standards, Measurements and Testing Programme (formerly BCR) has started a European collaborative project of which the aim is to test the feasibility of preparation of wastewater reference materials and the analytical state-of-the-art to enable the certification of trace elements in such matrices. This paper presents the results of the first phase of this project, namely the feasibility study and the results of an interlaboratory trial.

Speciation of methylmercury and Hg(II) using baker's yeast biomass (Saccharomyces cerevisiae). Determination by continuous flow mercury cold vapor generation atomic absorption spectrometry.

Baker's yeast cells (Saccharomyces cerevisiae) were successfully used to selectively separate methylmercury and Hg(II). Several parameters affecting the degree of biosorption and the binding kinetics of methylmercury and Hg(II) were evaluated: solution pH, temperature, incubation time, amount of biomass and analyte, and presence of foreign ions. Methylmercury is immediately bound to the yeast cells over a wide pH and temperature range. The fraction of methylmercury bound was in all cases 100% and was unaffected by the parameters mentioned above. Hg(II) has less affinity for yeast cells and remains in solution, although the percentage of Hg(II) bound to the cell does increase at high incubation time (3 h) and biomass. Of the foreign ions tested, chloride at high concentrations strongly increases the Hg(II) binding efficiency. Methylmercury and Hg(II) are quantitatively separated under optimum conditions, i.e., 30 min incubation time at pH 7.0 and 37 degrees C. The results were compared with those obtained using a purified S. cerevisiae isolate, and no significant differences were observed. Our work suggests that the cell rapidly reduces CH3Hg+ to more volatile species, such as Hg(I) or Hg0, whereas Hg2+ is slowly bound and reduced, perhaps because of the different toxicities of the two species. The method was applied to the selective determination of CH3Hg+ and Hg(II) in spiked water samples. In all cases good recoveries were obtained.

Evaluation of oxidant media for the determination of lead in food slurries by hydride generation atomic absorption spectrometry.

Several oxidant media were evaluated for the generation of lead hydride from slurry samples and their application to the determination of lead in vegetables and fish by hydride generation atomic absorption spectrometry. Three oxidant - acid media were compared: hydrogen peroxide - nitric acid, ammonium persulphate - nitric acid and potassium dichromate - lactic acid. The powdered samples were suspended in Triton X-100 and shaken with 10.0 g of blown zirconia spheres until a slurry was formed. The potassium dichromate - lactic acid medium was the most satisfactory for the determination of lead in fish and vegetables, providing the lowest detection limits as a result of its high sensitivity and low blank values. The ammonium persulphate - nitric acid medium gave good accuracy, precision and selectivity for vegetables (1-2 p.p.m. of lead); however, with fish (0.1-1 p.p.m. of lead) it was only a semi-quantitative medium for the determination of lead owing to its lack of sensitivity and selectivity. The hydrogen peroxide - nitric acid medium was unsatisfactory for the generation of lead hydride from slurry samples because of decomposition of hydrogen peroxide by the organic matter in the sample.