Novel bionanomaterial based on Spirulina maxima algae and graphene oxide for lead microextraction and determination in water and infant beverages.

A new hybrid bionanomaterial composed of graphene oxide (GO) and Spirulina maxima (SM) algae was synthesized and applied to develop a preconcentration method based on the dispersive micro-solid phase extraction (D-µ-SPE) technique for the determination of Pb in water and infant beverages. In this work, Pb(II) was extracted with 3 mg of the hybrid bionanomaterial (GO@SM) followed by a back-extraction step using 500 µL of 0.6 mol L-1 HCl. Then, a 1.5 × 10-3 mol L-1 dithizone solution was added to the sample containing the analyte to form a purplish red-colored complex for its detection by UV-Vis spectrophotometry at 553 nm. An extraction efficiency of 98% was obtained after optimization of experimental variables such as GO@SM mass, pH, sample volume, type, and time of agitation. A detection limit of 1 µg L-1 and a relative standard deviation of 3.5% (at 5 µg L-1 Pb(II), n = 10) were achieved. The calibration linear range was obtained between 3.3 and 95 µg L-1 Pb(II). The proposed method was successfully applied for the preconcentration and determination of Pb(II) in infant beverages. Finally, the greenness degree of the D-µ-SPE method was evaluated using the Analytical GREEnness calculator (AGREE), obtaining a score of 0.62.

Hybrid biomaterials to preconcentrate and determine toxic metals and metalloids: a review.

Toxic elements represent a serious threat to the environment and cause harmful effects on different environmental components, even at trace levels. These toxic elements are often difficult to detect through the typical instrumentation of an analytical laboratory because they are found at very low concentrations in matrices such as food and water. Therefore, preconcentration plays a fundamental role since it allows the effects of the matrix to be minimized, thus reaching lower detection limits and greater sensitivity of detection techniques. In recent years, solid-phase extraction has been successfully used for the preconcentration of metals as an environmentally friendly technique due to the fact that it eliminates or minimizes the use of reagents and solvents and offers reduced analysis times and low generation of waste in the laboratory. Hybrid biomaterials are low-cost, eco-friendly, and useful as efficient solid phases for the preconcentration of elements. In this review, recent investigations based on the use of hybrid biomaterials for the preconcentration and determination of toxic metals are presented and discussed, given special attention to bionanomaterials. A brief description of hybrid biomaterials often used for analytical purposes, as well as analytical techniques mostly used to characterize the hybrid biomaterials, is explained. Finally, the future prospects that encourage the search for new hybrid biomaterials are commented upon.

Elemental Speciation Analysis in Environmental Studies: Latest Trends and Ecological Impact.

Speciation analysis is a key aspect of modern analytical chemistry, as the toxicity, environmental mobility, and bioavailability of elemental analytes are known to depend strongly on an element's chemical species. Henceforth, great efforts have been made in recent years to develop methods that allow not only the determination of elements as a whole, but also each of its separate species. Environmental analytical chemistry has not ignored this trend, and this review aims to summarize the latest methods and techniques developed with this purpose. From the perspective of each relevant element and highlighting the importance of their speciation analysis, different sample treatment methods are introduced and described, with the spotlight on the use of modern nanomaterials and novel solvents in solid phase and liquid-liquid microextractions. In addition, an in-depth discussion of instrumental techniques aimed both at the separation and quantification of metal and metalloid species is presented, ranging from chromatographic separations to electro-chemical speciation analysis. Special emphasis is made throughout this work on the greenness of these developments, considering their alignment with the precepts of the Green Chemistry concept and critically reviewing their environmental impact.

Ultra-sensitive Sb speciation analysis in water samples by magnetic ionic liquid dispersive liquid-liquid microextraction and multivariate optimization.

Efficient separation and preconcentration of inorganic Sb species in different water samples were performed in this work by a novel dispersive liquid-liquid microextraction (DLLME) method based on the application of a magnetic ionic liquid (MIL) and electrothermal atomic absorption spectroscopy (ETAAS) detection. The Sb(iii) species was selectively extracted by complexation with ammonium diethyldithiophosphate (DDTP) and 45 µL of the MIL trihexyl(tetradecyl)phosphonium tetrachloroferrate ([P6,6,6,14]FeCl4) as extractant. Subsequently, a magnetic rod was applied for phase separation, introducing it directly into the sample solution, and the MIL phase was then diluted in chloroform. Afterwards, 15 µL of this solution was injected into the graphite furnace of ETAAS for Sb determination. A multivariate study was performed to obtain the optimal extraction conditions. Selective reduction of Sb(v) to Sb(iii) with 1% (w/v) KI before preconcentration was applied for total inorganic Sb determination and Sb(v) concentration was calculated by subtraction. The analytical performance of the method included extraction efficiencies of 98.0% for Sb(iii) and 92.6% for Sb(v), LOD of 0.02 µg L-1 for Sb(iii) and relative standard deviations of 3.1% for Sb(iii) and 3.5% for Sb(v) (at 6 µg L-1 Sb(iii) and Sb(v), n = 10). The calibration linear range was 0.08-20 µg L-1. The results showed that the proposed methodology was highly sensitive and selective for Sb speciation analysis in tap, dam, mineral, wetland, underground, rain and river water samples.

Determination of As in honey samples by magnetic ionic liquid-based dispersive liquid-liquid microextraction and electrothermal atomic absorption spectrometry.

A dispersive liquid-liquid microextraction (DLLME) method was developed based on the application of a magnetic ionic liquid (MIL) used as extractant phase for trace As determination in honey samples by electrothermal atomic absorption spectrometry (ETAAS). The procedure was simple, efficient and did not require a centrifugation stage. The As(III) species was preconcentrated by chelation with ammonium diethyldithiophosphate under acidic conditions at 3 mol L-1 HCl, followed by the extraction of the chelated analyte with the MIL trihexyl(tetradecyl)phosphonium tetrachloroferrate (III) ([P6,6,6,14]FeCl4) and acetonitrile as dispersant. The MIL phase containing the analyte was separated simply by a magnet. The collected aliquot of the MIL phase was injected directly into the graphite furnace of ETAAS for As determination. Under optimal experimental conditions, an extraction efficiency of 99% and a sensitivity enhancement factor of 110 were obtained. The limit of detection was 12 ng L-1 As and the relative standard deviation 3.9% (at 1 µg L-1 As and n = 10), calculated from the peak height of the absorbance signals. The linear range obtained was 0.02-5.0 µg L-1. This work reports the first application of the MIL [P6,6,6,14]FeCl4 along with the DLLME technique for the determination of As in honeys.

Magnetic ionic liquid-based dispersive liquid-liquid microextraction technique for preconcentration and ultra-trace determination of Cd in honey.

A simple, highly efficient, batch, and centrifuge-less dispersive liquid-liquid microextraction method based on a magnetic ionic liquid (MIL-DLLME) and electrothermal atomic absorption spectrometry (ETAAS) detection was developed for ultra-trace Cd determination in honey. Initially, Cd(II) was chelated with ammonium diethyldithiophosphate (DDTP) at pH 0.5 followed by its extraction with the MIL trihexyl(tetradecyl)phosphonium tetrachloroferrate(III) ([P6,6,6,14]FeCl4) and acetonitrile as dispersant. The MIL phase containing the analyte was separated from the aqueous phase using only a magnet. A back-extraction procedure was applied to recover Cd from the MIL phase using diluted HNO3 and this solution was directly injected into the graphite furnace of ETAAS instrument. An extraction efficiency of 93% and a sensitivity enhancement factor of 112 were obtained under optimal experimental conditions. The detection limit (LOD) was 0.4 ng L-1 Cd, while the relative standard deviation (RSD) was 3.8% (at 2 µg L-1 Cd and n = 10), calculated from the peak height of absorbance signals. This work reports the first application of the MIL [P6,6,6,14]FeCl4 along with the DLLME technique for the successful determination of Cd at trace levels in different honey samples. Graphical abstract Preconcentration of ultratraces of Cd in honey using a magnetic ionic liquid and dispersive liquid-liquid microextraction technique.

Ionic liquid-assisted separation and determination of selenium species in food and beverage samples by liquid chromatography coupled to hydride generation atomic fluorescence spectrometry.

Different ionic liquids (ILs) were assayed as mobile phase modifiers for the separation and determination of selenite [Se(IV)], selenate [Se(VI)], selenomethionine (SeMet) and Se-methylselenocysteine (SeMeSeCys) by reversed-phase high-performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry (RP-HPLC-HG-AFS). The use of several ILs: 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride ([C6mim]Cl), 1-octyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium bromide, 1-hexadecyl-3-methylimidazolium bromide and tributyl(methyl)phosphonium methylsulphate was evaluated. Also, the effect of pH, buffer type and IL concentration on the separation of Se species was studied. Complete separation was attained within 12min using a C8 column and a gradient performed with a mobile phase containing 0.1% (v/v) [C6mim]Cl at pH 6.0. The proposed method allows the separation of inorganic and organic Se species in a single chromatographic run, adding further benefits over already reported methods based on RP-HPLC. In addition, the influence of ILs on the AFS signals of each Se species was evaluated and a multivariate methodology was used for optimization of AFS sensitivity. The limits of detection were 0.92, 0.86, 1.41 and 1.19µgL-1 for Se(IV), Se(VI), SeMet and SeMeSeCys, respectively. The method was successfully applied for speciation analysis of Se in complex samples, such as wine, beer, yeast and garlic.

A comparative evaluation of different ionic liquids for arsenic species separation and determination in wine varietals by liquid chromatography - hydride generation atomic fluorescence spectrometry.

The application of different ionic liquids (ILs) as modifiers for chromatographic separation and determination of arsenite [As(III)], arsenate [As(V)], dimethylarsonic acid (DMA) and monomethylarsonic acid (MMA) species in wine samples, by reversed-phase high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry detection (RP-HPLC-HG-AFS) was studied in this work. Several factors influencing the chromatographic separation of the As species, such as pH of the mobile phase, buffer solution concentration, buffer type, IL concentration and length of alkyl groups in ILs were evaluated. The complete separation of As species was achieved using a C18 column in isocratic mode with a mobile phase composed of 0.5% (v/v) 1-octyl-3-methylimidazolium chloride ([C8mim]Cl) and 5% (v/v) methanol at pH 8.5. A multivariate methodology was used to optimize the variables involved in AFS detection of As species after they were separated by HPLC. The ILs showed remarkable performance for the separation of As species, which was obtained within 18min with a resolution higher than 0.83. The limits of detection for As(III), As(V), MMA and DMA were 0.81, 0.89, 0.62 and 1.00µg As L(-1). The proposed method was applied for As speciation analysis in white and red wine samples originated from different grape varieties.