Nano-bismuth sulfide based dispersive micro-solid phase extraction combined with energy dispersive X-ray fluorescence spectrometry for determination of mercury ions in waters

A selective method for the determination of mercury ions in different types of water samples by energy dispersive X-ray fluorescence spectrometry (EDXRF) was developed. Quantification of Hg(II) by EDXRF was preceded by ultra-sound assisted dispersive micro-solid phase extraction (USA-DMSPE) on nano-bismuth sulfide (nano-Bi2S3) as a solid sorbent. At pH 1 nano-Bi2S3 selectively adsorbs Hg(II) ions from aqueous samples with an adsorption capacity of 499.1 mg g -1. The experimental data fitted well with the Langmuir isotherm model, which confirms the chemical character of the adsorption process. Under optimized preconcentration conditions, i.e. a sample pH of 1, adsorbent mass of 1 mg, sample volume of 50 mL and sonication time of 15 min, the linear response between fluorescence radiation intensity and the metal concentration was obtained within 1–200 ng mL -1 range with a correlation coefficient of 0.9988. The method allows the detection of mercury ions at a concentration of only 0.06 ng mL -1. The determination of Hg(II) ions after the nano-Bi2S3 based USA-DMSPE-EDXRF procedure is possible even in the presence of a high concentration of anions and cations typically coexisting in surface waters. The described method was applied to the determination of Hg(II) ions in mineral, spring, river, and artificial sea waters. The correctness of the procedure was confirmed by analysis of the certified reference material (Seawater QC3163)

Ultrasound-assisted dispersive micro-solid phase extraction using molybdenum disulfide supported on reduced graphene oxide for energy dispersive X-ray fluorescence spectrometric determination of chromium species in water

Molybdenum disulfide (MoS2) was supported on graphene oxide (GO) by hydrothermal method. The resulting nanocomposite (MoS2-rGO) was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The experiments show that at pH 2, MoS2-rGO has a great affinity for adsorption of hexavalent chromium ions while Cr(III) ions remain in aqueous sample. In the adsorption process, the dominant role plays chemisorption. The determined adsorption capacity is 583.5 mg g−1. Parameters affecting the extraction process, namely sample pH, sample volume, contact time, and matrix ions, were investigated by sequential batch tests. Under optimal conditions (pH 2, sample volume 50 mL, sonication time 10 min, adsorbent mass 1 mg), the calibration curve covers the 1–200 ng mL−1 range with a correlation coefficient (R2) of 0.998. The recovery of the method is 97 ± 3%. Other data of merit include a relative standard deviation of < 3.5%, enrichment factor of 3350, and detection limit of 0.050 ng mL−1. The accuracy of the method was confirmed by analysis of the reference materials QC1453 (chromium VI in drinking water) and QC3015 (chromium VI in seawater). The method was successfully applied to chromium speciation in water samples, including high salinity ones. The concentration of Cr(III) was calculated as the difference between the total concentration of chromium (after oxidation of Cr(III) to Cr(VI) with potassium permanganate) and the initial Cr(VI) content

Speciation of inorganic chromium in water samples by energy dispersive X-ray fluorescence spectrometry

A simple and effective speciation procedure for the determination of inorganic chromium species in water samples was developed.</p

Preconcentration of Zn, Cu, and Ni Ions from Coffee Infusions via 8-Hydroxyquinoline Complexes on Graphene Prior to Energy Dispersive X-ray Fluorescence Spectrometry Determination

A simple and effective preconcentration procedure based on dispersive micro solid-phase extraction prior to energy dispersive X-ray fluorescence spectrometric (EDXRF) determination of trace amounts of Ni, Cu, and Zn in coffee infusions was proposed. The method is based on the adsorption of 8-hydroxyquinoline metal complexes on micro amounts of graphene nanoparticles. In order to optimize adsorption process, the influence of some parameters such as pH, graphene mass, concentration of 8-hydroxyquinoline (8-HQ) and Triton X-100, sample volume, and sorption time were examined. At optimal preconcentration conditions, calibration curves were linear from 1 to 150 ng mL−1 for Ni and Cu and from 1 to 200 ng mL−1 for Zn. The recoveries of the metal ions were in the 95–98% range with the precision lower than 4.6%. The obtained detection limits were 0.08 ng mL−1 for Ni and 0.09 ng mL−1 for Cu and Zn. The proposed method was successfully applied to determination of Ni, Cu, and Zn in coffee infusions. Accuracy and repeatability of the proposed procedure were confirmed by the standard addition method and compared to the results obtained by ICP-OES technique. </jats:p