Determination of total Sb, Se, Te, and Bi and evaluation of their inorganic species in garlic by hydride-generation–atomic-fluorescence spectrometry

Elucidation of tellurium biogenic nanoparticles in garlic, Allium sativum, by inductively coupled plasma-mass spectrometry

BACKGROUND

Biosynthesis of Te nanoparticles may occur in higher plants exposed to Te, as reported on microorganisms. However, unambiguous observations of the biogenic nanoparticles (BgNPs) of Te in plants are lacking. Hence, in this study, we investigated the formation of insoluble BgNPs of Te in garlic (Allium sativum) as a model plant.

METHOD

We performed elemental analysis based on inductively coupled plasma-mass spectrometry (ICP-MS) technique, and obtained Te concentration and distribution in various parts of garlic. In addition, insoluble Te particles were detected by fast time-resolved ICP-MS. Direct observation of the insoluble Te particle was also conducted by scanning electron microscope (SEM) and transmission electron microscope (TEM).

RESULTS

A part of the roots and clove from Te-exposed garlic showed black coloration. Te concentrations in the black-colored parts were significantly increased compared with the non-colored parts. Transient signals of Te unique to nanoparticles were detected from the insoluble fractions of the black-colored parts. Finally, rod-shaped biogenic Te nanoparticles consisting of highly crystalline elemental Te was observed by SEM and TEM.

CONCLUSION

Our data provide new insights to the metabolic pathway of Te in higher plants for the formation of insoluble biogenic nanoparticles, which is extremely important for the detoxification of Te.

Fluorescence Sensors for Bismuth (III) Ion from Pyreno[4,5-d]imidazole Derivatives

Three pyreno[4,5-d]imidazole derivatives are synthesized and evaluated as fluorescent sensors for bismuth (III) ion. The target compounds are prepared in 55-86% yields from a condensation reaction between pyrene-4,5-dione and aromatic aldehydes. The compound bearing a phenolic group can selectively detect bismuth (III) ion via fluorescence enhancement with a detection limit of 1.20 μm in CH₃ CN-DMSO mixture and 3.40 μm in 10% pH5 aqueous in CH₃ CN-DMSO mixture. The sensing mechanism involving a formation of coordination complex is investigated by UV-VIS and fluorescence titrations, ¹ H-NMR and the decomplexation of the bismuth complex by sulfide ion. The application of this sensor for quantitative analysis of spiked bismuth (III) ion in real water samples from two different sources is demonstrated.

An efficient new dual fluorescent pyrene based chemosensor for the detection of bismuth (III) and aluminium (III) ions and its applications in bio-imaging

A new simple pyrene based schiff base chemosensor 1 (nicotinic acid pyren-1-ylmethylene-hydrazide) has been constructed and is prepared from 1-pyrenecarboxaldehyde and nicotinic hydrazide. Notably, the chemosensor 1 exhibited remarkable colour changes while in the presence of trivalent metal ions like Bi³⁺ & Al³⁺ ion in DMSO-H₂O, (1:1 v/v, HEPES = 50 mM, pH = 7.4). The UV-Vis spectral investigation of chemosensor 1 showed that the maximum absorption peak appeared at 378 nm. In emission studies, chemosensor 1 develops weak fluorescence, while upon the addition of Bi³⁺ and Al³⁺ ions, it exhibits an enhancement of fluorescence intensity. Nevertheless, rest of metal ions have no changes in the emission spectra. The association constant of chemosensor 1 for binding to Bi³⁺ & Al³⁺ system had a value of 1.27 × 10⁴ M^-1 and 1.53 × 10⁴ M^-1. The detection limits were 0.12 µM for Bi³⁺ and 0.17 µM for Al³⁺ respectively. The overall results reveal that chemosensor 1 can act as a dual-channel, highly selective, and sensitive probe for Bi³⁺ and Al³⁺ ions. Moreover, the fluorescence imaging of chemosensor 1 was applied in RAW 264.7 cell line and cytotoxicity assay prove that this chemosensor 1 is non-toxic as well as highly biocompatible.

Evaluation of the Content of Antimony, Arsenic, Bismuth, Selenium, Tellurium and Their Inorganic Forms in Commercially Baby Foods

Baby foods, from the Spanish market and prepared from meat, fish, vegetables, cereals, legumes, and fruits, were analyzed to obtain the concentration of antimony (Sb), arsenic (As), bismuth (Bi), and tellurium (Te) as toxic elements and selenium (Se) as essential element. An analytical procedure was employed based on atomic fluorescence spectroscopy which allowed to obtain accurate data at low levels of concentration. Values of 14 commercial samples, expressed in nanograms per gram fresh weight, ranged for Sb 0.66-6.9, As 4.5-242, Te 1.35-2.94, Bi 2.18-4.79, and Se 5.4-109. Additionally, speciation studies were performed based on data from a non-chromatographic screening method. It was concluded that tellurium and bismuth were mainly present as inorganic forms and selenium as organic form, and antimony and arsenic species depend on the ingredients of each baby food. Risk assessment considerations were made by comparing dietary intake of the aforementioned elements through the consumption of one baby food portion a day and recommended or tolerable guideline values.

Critical evaluation of strategies for single and simultaneous determinations of As, Bi, Sb and Se by hydride generation inductively coupled plasma optical emission spectrometry

A systematic study of hydride generation (HG) of As, Bi, Sb and Se from solutions containing As(III), As(V), Bi(III), Sb(III), Sb(V), Se(IV) and Se(VI) was presented. Hydrides were generated in a gas-liquid phase separation system using a continuous flow vapor generation accessory (VGA) by mixing acidified aqueous sample, HCl and sodium borohydride reductant (NaBH₄) solutions on-line. For detection, a simultaneous axially viewed inductively coupled plasma optical emission spectrometer (ICP-OES) was applied. Effects of the HCl concentration (related to sample and additional acid solutions) and type of the pre-reducing agents used for reduction of As(V), Sb(V) and Se(VI) into As(III), Sb(III) and Se(IV) on the analytical responses of As, Bi, Sb and Se were studied and discussed. Two compromised HG reaction conditions for simultaneous measurements of As+Bi+Sb (CC1) or As+Sb+Se (CC2) were established. It was found that choice of the pre-reductant prior to formation of the hydrides is critical in obtaining the dependable results of the analysis. Accordingly, for a As(III)+As(V)+Bi(III)+Sb(III)+Sb(V) mixture and using CC1, thiourea/thiourea-ascorbic acid interfered in Bi determination and hence, total As+Sb could be measured. If L-cysteine/L-cysteine-ascorbic acid were used, measurements of total Bi+Sb was possible in these HG reaction conditions. For a As(III)+As(V)+Sb(III)+Sb(V)+Se(IV)+Se(VI) mixture and using CC2, thiourea/thiourea-ascorbic acid and L-cysteine/L-cysteine-ascorbic acid influenced HG of Se but ensured total As+Sb determination. In contrast, heating a sample solution with HCl, although did not pre-reduce As(V) and Sb(V), assured quantitative reduction of Se(VI) to Se(IV). Finally, considering all favorable pre-reducing and HG conditions, methodologies for reliable determination of total As, Bi, Sb and Se by HG-ICP-OES were proposed. Strategies for single-, two- and three-element measurements were evaluated and validated, obtaining the detection limits (DLs) below 0.1ngg^-1 and precision typically in the range of 1.4-3.9% RSD.

Separation/preconcentration of ultra-trace levels of inorganic Sb and Se from different sample matrices by charge transfer sensitized ion-pairing using ultrasonic-assisted cloud point extraction prior to their speciation and determination by hydride generation AAS

In the existing study, a new, simple and low cost process for separation/preconcentration of ultra-trace level of inorganic Sb and Se from natural waters, beverages and foods using ultrasonic-assisted cloud point extraction (UA-CPE) prior to their speciation and determination by hydride generation AAS, is proposed. The process is based on charge transfer sensitized complex formations of Sb(III) and Se(IV) with 3-amino-7-dimethylamino-2-methylphenazine hydrochloride (Neutral red, NRH(+)) in presence of pyrogallol and cetyltrimethylammonium bromide (CTAB) as both sensitivity enhancement and counter ion at pH 6.0. Under the optimized reagent conditions, the calibration curves were highly linear in the ranges of 8-300ngL(-1) and 12-250ngL(-1) (r(2)≥0.993) for Se(IV) and Sb(III), respectively. The limits of detection were 2.45 and 3.60ngL(-1) with sensitivity enhancement factors of 155 and 120, respectively. The recovery rate was higher than 96% with a relative standard deviation lower than 5.3% for five replicate measurements of 25, 75 and 150ngL(-1) Se(IV) and Sb(III), respectively. The method was validated by analysis of two certified reference materials (CRMs), and was successfully applied to the accurate and reliable speciation and determination of the contents of total Sb/Sb(III), and total Se/Se(IV) after UA-CPE of the pretreated sample matrices with and without pre-reduction with a mixture of l-cysteine and tartaric acid. Their Sb(V) and Se(VI) contents were calculated from the differences between total Sb and Sb(III) and/or total Se and Se(IV) levels.

Graphene oxide-TiO2 composite solid phase extraction combined with graphite furnace atomic absorption spectrometry for the speciation of inorganic selenium in water samples

In this paper, a method of graphene oxide (GO)-TiO2 composite solid phase extraction followed by graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the speciation of inorganic selenium in environmental waters. The adsorption behavior of inorganic Se(IV) and Se(VI) on the GO-TiO2(1:1) composite was investigated. It was found that Se(IV) was quantitatively retained on the GO-TiO2 composites within a wide pH range of 0.5-10, while Se(VI) was quantitatively adsorbed on GO-TiO2(1:1) composite at pH 0.5-2, and no obvious adsorption of Se(VI) within the pH range of 4-10 was found. By selecting pH 6.0, Se(IV) could be easily determined. After reduction of Se(VI), total Se was determined by the proposed method, and Se(VI) was calculated as the difference between the total Se and Se(IV). The factors affecting the separation/preconcentration of Se(IV) and Se(VI) were studied. Under the optimum conditions, the isothermal adsorption of Se(IV) on the GO-TiO2(1:1) composite fitted Langmuir model; a linear range over 0.1-12ngmL(-1) was obtained. The limit of detection (LOD) and precision of the method for Se(IV) was 0.04ngmL(-1) and 9.4% (cSe(IV)=0.5ngmL(-1), n=7), respectively. In order to verify the accuracy of the method, a standard water sample (GSBZ50031-94) was analyzed, and the determined value was in a good agreement to the certified value. The established method was applied to inorganic Se speciation in environmental water samples and the recovery of 87.4-102% was obtained for the spiked samples.

Determination of trace amounts of Se(IV) by hydride generation atomic fluorescence spectrometry after solid-phase extraction using magnetic multi-walled carbon nanotubes

A sensitive and simple method using magnetic multi-walled carbon nanotubes, as an adsorbent, has been successfully developed for extraction and preconcentration trace amounts of Se(IV) with detection by hydride generation atomic fluorescence spectrometry. The prepared nanoparticles were confirmed by Fourier transform infrared spectra, X-ray diffraction spectrometry, vibrating sample magnetometry, and transmission electron microscopy. These magnetic nanocomposites can be easily dispersed in aqueous samples and retrieved by the application of external magnetic field via a piece of permanent magnet. The main factors affecting the signal intensity such as sample pH value, adsorbent amount, eluent concentration and volume, sample volume, and coexisting ions have been investigated and established. The absorbent could be repeatedly used at least 100 times. The enhancement factor of the proposed method for Se(IV) was 100. The method had a linear calibration plot in the range from 0.05 to 10.0 μg L(-1) with a standard deviation of 2.3% at 0.5 μg L(-1) (n=11). The limit of detection was as low as 0.013 μg L(-1). Accuracy of the method was evaluated by the analysis of water samples and certified reference materials.

Speciation and determination of ultra trace amounts of inorganic tellurium in environmental water samples by dispersive liquid-liquid microextraction and electrothermal atomic absorption spectrometry

A simple and powerful method has been developed for the rapid and selective determination of Te(IV) and Te(VI), employing dispersive liquid-liquid microextraction combined with electrothermal atomic absorption spectrometry using palladium as permanent modifier. Under acidic conditions pH 1, only Te(IV) can form a complex with ammonium pyrrolidine dithiocarbamate (APDC) and therefore be extracted into fine droplets of carbon tetrachloride (extraction solvent) which are dispersed with ethanol into the water sample solution. After centrifugation, Te(IV) was determined in the sedimented organic phase while Te(VI) remained in the aqueous phase. Total inorganic tellurium was determined after the reduction of the Te(VI) to Te(IV). Te(VI) was calculated as the difference between the measured total inorganic tellurium and Te(IV) content. The effective parameters for improving the efficiency of microextraction process were investigated by using experimental and central composite designs. Under optimal conditions the enrichment factor was 125 and the calibration graph was linear in the range of 0.015-1 ng mL(-1) with detection limit and characteristic mass of 0.004 ng mL(-1) and 0.033 pg, respectively. The relative standard deviation for 0.5 ng mL(-1) of tellurium measurement was 3.6% (n=6) at ash and atomization temperature, 900 and 2600 degrees C, respectively. The recoveries of spiked Te(IV) and Te(VI) to the environmental water samples were 89.6-101.3% and 96.6-99.1%, respectively. The accuracy is also evaluated by applying the proposed method to certified reference material (NIST SRM 1643e), for which the result was in a good agreement with the certified values reported for this CRM (95% confidence level).