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

Abstract

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. Graphical abstract

Potentiodynamic Electrochemical Impedance Spectroscopy of Polyaniline-Modified Pencil Graphite Electrodes for Selective Detection of Biochemical Trace Elements

“…Generally, spectral, optical, and electrochemical methods are major approaches used to determine the ions in aqueous solutions. Inductively coupled plasma, coupled with mass spectroscopy, optical, and/or atomic emission spectrometry [ 5 ] as well as X-ray fluorescence spectrometry (XRF) [ 6 ], is among the highly mature spectral and optical techniques for ppm- and ppb-level detection of trace elements in complicated matrices. However, long incubation time, bulky and costly equipment, multi-step sample preparation processes, and requiring chromatographic methods for metal ion speciation are some bottlenecks for real-time monitoring of metal ions using spectral techniques [ 7 ].…”

“…In recent years, pencil graphite electrodes (PGE) have been used as electrode material in many sensing studies due to their low cost, high omnipresence, disposability, high mechanical stability, and analytical reproducibility (e.g., [13]). PGE is able to provide reproducible, voltametric peaks and a fast rate of electron transfer for usual Fe(CN) 6 3−/4− and Ru(NH 3 ) 6 3+/2+ redox systems [14]. Despite its other electrochemical benefits (high reactivity, low background current, etc.…”

Application of Metallic Nanoparticles and Their Hybrids as Innovative Sorbents for Separation and Pre-concentration of Trace Elements by Dispersive Micro-Solid Phase Extraction: A Minireview

“…There are also studies in which no desorption procedure has been outlined. Instead, following extraction, the sorbent and the adsorbed analyte have been filtered off, dried and submitted for analysis along with the filter (Baranik et al, 2018a , b ; Pytlakowska et al, 2020a , b ). This type of procedure appears to be advantageous if the analyte is quantified by means of energy dispersive X-ray fluorescence spectrometry (EDXRF).…”

“…This type of procedure appears to be advantageous if the analyte is quantified by means of energy dispersive X-ray fluorescence spectrometry (EDXRF). The enrichment factor (EF) of 3350, which was calculated as a ratio of sensitivity of DMSPE–EDXRF procedure to sensitivity of the direct EDXRF measurement and reported by Pytlakowska et al ( 2020a ), can be considered abnormally high.…”

“…Pytlakowska et al ( 2020a , b ) ran experiments on two variants of graphene, graphene oxide (GO) and reduced graphene oxide (rGO), coupled with molybdenum disulfide (MoS 2 ) in order to investigate the potential of the hybrid material for the adsorption of metal ions. MoS 2 was supported on GO by hydrothermal method.…”