Pressurized liquid extraction of organometals and its feasibility for total metal extraction

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.

A new method for total mercury and methyl mercury analysis in muscle of seawater fish

In this work we have developed a cost-effective method for the analysis of methyl mercury (MeHg) in seawater fish muscle. The novelty of this method lies in the use of microwave-assisted extraction with acidic solution (HCl), addition of toluene, and subsequent extraction with cysteine acetate solution where only MeHg is present because of its affinity for cysteine groups. MeHg in cysteine phase and total mercury in the homogenate muscle tissue were determined using a direct Hg analyzer (DMA-80). Validation, precision, and accuracy of the method were evaluated and monitored with a tuna fish certified reference material (CRM 463) containing MeHg.

Development of a new sample pre-treatment procedure based on pressurized liquid extraction for the determination of metals in edible seaweed

A new, simple, fast and automated method based on acetic acid-pressurized liquid extraction (PLE) has been developed for the simultaneous extraction of major and trace elements (As, Ca, Cd, Co, Cr, K, Mg, Mn, Na, Pb, Sr and Zn) from edible seaweeds. The target elements have been simultaneously determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The influence of several extraction parameters (e.g. acetic acid concentration, extraction temperature, extraction time, pressure, number of cycles, particle size and diatomaceous earth (DE) mass/sample mass ratio) on the efficiency of metal leaching has been evaluated. The results showed that metal extraction efficiency depends on the mass ratio of the dispersing agent mass and the sample. The optimized procedure consisted of the following conditions: acetic acid (0.75 M) as an extracting solution, 5 min of extraction time, one extraction cycle at room temperature at a pressure of 10.3 MPa and addition of a dispersing agent (at a ratio of 5:1 over the sample mass). The leaching procedure was completed after 7 min (5 min extraction time plus 1 min purge time plus 1 min end relief time). Limits of detection and quantification and repeatability of the over all procedure have been assessed. Method validation was performed analysing two seaweed reference materials (NIES-03 Chlorella Kessleri and NIES-09 Sargasso). The developed extraction method has been applied to red (Dulse and Nori), green (Sea Lettuce) and brown (Kombu, Wakame and Sea Spaghetti) edible seaweeds.

Determination of major and trace elements in human scalp hair by pressurized-liquid extraction with acetic acid and inductively coupled plasma–optical-emission spectrometry

An analytical method has been developed for determination of major (Ca, K, Mg, and Na) and trace elements (As, Cd, Co, Li, Ni, and Sr) in human scalp hair. The proposed method includes a novel, simple, rapid, highly efficient, and automated metal-leaching procedure, by pressurized-liquid extraction (PLE), combined with a rapid simultaneous detection system-inductively coupled plasma-optical-emission spectrometry (ICP-OES). PLE is one of the most promising recently introduced sample-preparation techniques, with the advantages of reducing solvent consumption and enabling automated sample handling. The operating conditions for PLE, including concentration of the extraction solvent, extraction temperature, static time, number of extraction steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio, and flush volume were studied using an experimental design (Plackett-Burman design, PBD). The optimum conditions were use of 0.75 mol L-1 acetic acid as extracting solution and powdered hair samples thoroughly mixed with DE, as a dispersing agent, at a DE mass/sample mass ratio of 4. Extraction was performed at room temperature and an extraction pressure of 140 atm for 5 min in one extraction step. The flush volume was fixed at 60%. The PLE-assisted multi-element leaching proposed is complete after 7 min (5 min static time plus 1 min purge time plus 1 min end relief time). Under the optimised conditions the figures of merit, for example limits of detection and quantification, repeatability of the over-all procedure, and accuracy, were evaluated. Analysis of GBW-07601 (human hair) certified reference material revealed accuracy was good for the target elements. The optimised method was finally applied to several human scalp-hair samples.

Pressurized liquid extraction as a novel sample pre-treatment for trace element leaching from biological material

Pressurized liquid extraction (PLE), commonly used for organic compounds extraction, has been applied for trace element leaching from marine biological material in order to determine major and trace elements (Al, As, Cd, Co, Cu, Fe, Hg, Li, Mn, Pb, Se, Sr, V and Zn). The released elements by formic acid PLE have been evaluated by inductively coupled plasma-optical emission spectrometry (ICP-OES). Different variables, such as formic acid concentration, extraction temperature, static time, extraction steps, pressure, mean particle size and diatomaceous earth (DE) mass/sample mass ratio were simultaneously studied by applying an experimental design approach (Plackett-Burman design (PBD) and central composite design (CCD)). Results showed that the extraction temperature was statistically significant (confidence interval of 95%) for most of the elements (high metal releasing was achieved at high temperatures). In addition, formic acid concentration was also statistically significant (confidence interval of 95%) for metals such as Cd and Cu. Most of the metals can be extracted using the same PLE operating conditions (formic acid concentration of 1.0 M, extraction temperature at 125 degrees C, static time of 5 min, one extraction step, extraction pressure at 500 psi and DE mass/sample mass ratio of 2). Taking in mind PLE requirements at the optimised operating conditions (125 degrees C), a time of 6 min is needed to pre-heat the cell. Therefore, the PLE assisted multi-element leaching is completed after 12 min. Analytical performances, such as limits of detection and quantification, repeatability of the over-all procedure and accuracy, by analysing GBW-08571, DORM-2, DOLT-3 and TORT-2 certified reference materials, were finally assessed.