Determination of silver in biological reference materials by neutron activation analysis

Development of a selective and sensitive colour reagent for gold and silver ions and its application to desktop scanner analysis

Desktop scanners can be favorable alternatives to sophisticated spectrophotometers for the assessment of analytes in complex real samples. Distinctively, our method has been thoroughly investigated, optimized, validated and successfully applied to the assessment of silver and gold in complex real samples, applying syringal rhodanine (SR) as a novel specifically tailored chromogenic reagent and using a desktop scanner as a versatile sensor. Maximum colour absorbance was obtained in the presence of cetylpyridinium chloride (CPC) and cetyltrimethylammonium chloride (CTAC) for silver and gold chelates, respectively. For each metal ion, two ternary complexes were formed depending on the SR concentration with stoichiometries of 1 : 1 : 1 and 1 : 2 : 3 (Ag–SR–CPC) and 1 : 2 : 3 and 1 : 3 : 4 (Au–SR–CTAC), respectively. The methods adhered to Beer's law for 0.15–2.5 and 0.15–2.25 μg mL⁻¹ with detection limits of 0.0089 and 0.0163 μg mL⁻¹ for silver and gold, respectively. The molar absorptivities were 3.63 × 10⁴ and 6.15 × 10⁴ L mol⁻¹ cm⁻¹ at 550 nm and 554 nm, with Sandell's sensitivity indexes of 0.0029 and 0.0032 μg cm⁻², respectively. The method was successfully applied to the assessment of silver and gold in a wide range of complex environmental samples.

Desktop scanners can be favorable alternatives to sophisticated spectrophotometers for the assessment of analytes in complex real samples.

Sensitive and selective localized surface plasmon resonance light-scattering sensor for Ag+ with unmodified gold nanoparticles

A novel localized surface plasmon resonance (LSPR) light-scattering sensor for Ag(+) was developed with unmodified gold nanoparticles (AuNPs), based upon the specific recognition property of Ag(+) with a cytosine-cytosine mismatched base pair. The addition of Ag(+) induced the oligonucleotide 5'-TAC ATA CAT ACT ATC TAT CTA-3' to be desorbed from the surface of the AuNPs, resulting in the aggregation of AuNPs, accompanied by a dramatic enhancement of the LSPR light-scattering intensity. The enhancement of LSPR light-scattering intensity was proportional to the concentration of Ag(+) in the range of 0.13-1.12 μM, with a limit of detection of 62.0 nM. The results were also proved by a colorimetric method. Furthermore, this method can provide satisfactory results for the determination of Ag(+) in water samples and industrial products.

Bioaccumulation of silver in ectomycorrhizal and saprobic macrofungi from pristine and polluted areas

Macrofungi are effective accumulators of Ag. This study provides a comprehensive review of this phenomenon supported by original data on the Ag concentrations of macrofungi from pristine and Ag-polluted areas. In pristine areas, the median Ag concentrations of ectomycorrhizal (ECM) and saprobic (SAP) macrofungi were 0.79 and 2.94 mg kg(-1), respectively. In these areas, hyperaccumulation thresholds for Ag in ECM and SAP macrofungi are proposed as 100 and 300 mg kg(-1), respectively. In a Ag-polluted area, the Ag concentrations in macrofungi (ECM and SAP) were significantly elevated with the median value of 24.7 mg kg(-1) and the highest concentrations in Amanita spp. of the section Vaginatae (304-692 mg kg(-1)). The intracellular speciation of Ag in fruit-bodies of the Ag-accumulator Amanita submembranacea was inspected by size exclusion chromatography followed by sulfhydryl-specific fluorimetric assays of ligands using reverse phase high-performance liquid chromatography and improved polyacrylamide gel electrophoresis. Virtually all Ag was found to be intracellular and sequestered in the major 7 kDa and minor 3.3 kDa complexes. The lack of glutathione and phytochelatins and the presence of a single 3 kDa sulfhydryl-containing peptide in the isolated Ag-complexes suggest that detoxification of Ag in A. submembranacea may rely on metallothionein. Vertical distribution of Ag in a polluted forest soil profile has shown substantial enrichment in organic horizons; in polluted technosol, the highest Ag concentrations were found in surface layers. Standardized EDTA extraction of Ag in both the investigated soil profiles showed relatively low Ag extractibility, generally within the range of 2.2-7.7% of total Ag content.