Occupational exposure to Cr is concerning because of its myriad of health effects. Assessing chromium exposure is also cost and resource intensive because the analysis typically uses sophisticated instrumental techniques like inductively coupled plasma-mass spectrometry (ICP-MS). Here, we report a novel, simple, inexpensive microfluidic paper-based analytical device (μPAD) for measuring total Cr in airborne particulate matter. In the μPAD, tetravalent cerium (Ce(IV)) was used in a pretreatment zone to oxidize all soluble Cr to Cr(VI). After elution to the detection zone, Cr(VI) reacts with 1,5-diphenylcarbazide (1,5-DPC) forming 1,5-diphenylcarbazone (DPCO) and Cr(III). The resulting Cr(III) forms a distinct purple colored complex with the DPCO. As proof-of-principle, particulate matter (PM) collected on a sample filter was analyzed with the μPAD to quantify the mass of total Cr. A log-linear working range (0.23–3.75 μg; r2 = 0.998) between Cr and color intensity was obtained with a detection limit of 0.12 μg. For validation, a certified reference containing multiple competing metals was analyzed. Quantitative agreement was obtained between known Cr levels in the sample and the Cr measured using the μPAD. 相似文献
Inorganic mercury ions (Hg2+) in laboratory prepared solutions were determined with a screen-printed carbon electrode (SPCE) coated with a polyaniline-methylene blue (PANI-MB) polymer layer. The structure and properties of the PANI-MB polymer layer were compared to that of normal polyaniline (PANI) in order to elucidate the structure of the PANI-MB layer. The electrically-conducting polymers were prepared by electrochemical polymerisation of monomer solutions of aniline, and mixed solutions of aniline with methylene blue onto respective screen-printed carbon electrodes (SPCEs). Scanning Electron Microscopy (SEM) analyses of the SPCE polymer coated electrodes have shown that nanostructured materials have formed with the diameters of the PANI nanoclusters and PANI-MB nanorods at approximately 200 nm. Anodic stripping voltammetry (ASV) was used to evaluate a solution composed of 1 × 10?6 M Hg2+, in the presence of the SPCE/PANI-MB polymer sensor electrode. The Hg2+ ions were determined as follows: (i) pre-concentration and reduction on the modified electrode surface and (ii) subsequent stripping from the electrode surface during the positive potential sweep. The experimental conditions optimised for Hg2+ determination included the supporting electrolyte concentration and the accumulation time. The results obtained have shown that the SPCE/PANI-MB polymer sensor electrode operates optimally at a pH 2, with the supporting electrolyte concentration at 0.5 M HCl. A linear calibration curve was found to be in the range of 1 × 10?8 M to 1 × 10?5 M Hg2+ after 120 s of pre-concentration. The detection limit was calculated and found to be 54.27 ± 3.28 µg L?1 of Hg2+. The results have also shown that a conducting polymer modified SPCE sensor electrode can be used as an alternative transducer for the voltammetric stripping and analysis of inorganic Hg2+ ions. 相似文献
A simple and reliable method for Hg determination in fish samples has been developed. Lyophilised fish tissue samples were extracted in a 25% (w/v) tetramethylammonium hydroxide (TMAH) solution; the extracts were then analysed by FI-CVAFS. This method can be used to determine total and inorganic Hg, using the same FI manifold. For total Hg determination, a 0.1% (w/v) KMnO4 solution was added to the FI manifold at the sample zone, followed by the addition of a 0.5% (w/v) SnCl2 solution, whereas inorganic Hg was determined by adding a 0.1% (w/v) L-cysteine solution followed by a 1.0% (w/v) SnCl2 solution to the FI system. The organic fraction was determined as the difference between total and inorganic Hg. Sample preparation, reagent consumption and parameters that can influence the FI-CVAFS performance were also evaluated. The limit of detection for this method is 3.7 ng g?1 for total Hg and 4.3 ng g?1 for inorganic Hg. The relative standard deviation for a 1.0 µg L?1 CH3Hg standard solution (n = 20) was 1.1%, and 1.3% for a 1.0 µg L–1 Hg2+ standard solution (n = 20). Accuracy was assessed by the analysis of Certified Reference Material (dogfish: DORM-2, NRCC). Recoveries of 99.1% for total Hg and 93.9% inorganic Hg were obtained. Mercury losses were not observed when sample solutions were re-analysed after a seven day period of storage at 4°C. 相似文献
Simple cyclic renewable silver amalgam film electrode (Hg(Ag)FE), applied for the determination of gallium(III) using differential pulse anodic stripping voltammetry (DP ASV), is presented. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimised. The calibration graph is linear from 5?nM (0.35?µg?L?1) to 80?nM (5.6?µg?L?1) for a preconcentration time of 60?s, with correlation coefficient of 0.995. For a Hg(Ag)FE with a surface area of 9.9?mm2 the detection limit for a preconcentration time of 120?s is as low as 0.1?µg?L?1. The repeatability of the method at a concentration level of the analyte as low as 3.5?µg?L?1, expressed as RSD is 3.2% (n?=?5). The proposed method was successfully applied by studying the synthetic samples and simultaneously recovery of Ga(III) from spiked aluminium samples. 相似文献
Heteronuclear complexes {[Hg(R)2][Au(R′)(PMe3)]2}n (R=R′=C6Cl2F3 ( 3 ); R=R′=C6F5 ( 4 ); R=C6Cl2F3, R′=C6F5 ( 5 ); R=C6F5, R′=C6Cl2F3 ( 6 )) were prepared by the treatment of the corresponding organomercury compounds, [Hg(C6X5)2], with two equivalents of [Au(C6X5)(PMe3)]. Their crystal structures, as determined by using X‐ray diffraction methods, display Au???Hg interactions. Although only compound 4 and 5 show luminescence in the solid state, all of these compounds quench the fluorescence of naphthalene in solution. Solution studies of these derivatives suggest a cooperative effect of the gold(I) center in switching on the quenching capabilities of the [Hg(C6X5)2] synthon with naphthalene. Theoretical studies confirmed the quenching ability of the organomercury species in the presence of gold. 相似文献
Cellulose was modified via chlorination using phosphorous oxychloride followed by functionalization with amine and thiol moieties. The obtained modified cellulose samples were investigated by means of FTIR, TGA, TEM, and nitrogen-adsorption surface area (BET). The BET measurements showed a remarkable increase in the surface area of Cell-N-S (477.7 m2/g) and Cell-N (706 m2/g). The resins gave an uptake capacities of 38 and 7.2mmol/g for Cell-N-S and Cell-N, respectively toward Hg(II) from its solutions. These values are considered much better compared with other reported resins. Regeneration of the resins was achieved effectively using acidified thiourea. 相似文献
A hypercrosslinked conjugated microporous polymer (HCMP‐1) with a robustly efficient absorption and highly specific sensitivity to mercury ions (Hg2+) is synthesized in a one‐step Friedel–Crafts alkylation of cost‐effective 2,4,6‐trichloro‐1,3,5‐triazine and dibenzofuran in 1,2‐dichloroethane. HCMP‐1 has a moderate Brunauer–Emmett–Teller specific surface (432 m2 g−1), but it displays a high adsorption affinity (604 mg g−1) and excellent trace efficiency for Hg2+. The π–π* electronic transition among the aromatic heterocyclic rings endows HCMP‐1 a strong fluorescent property and the fluorescence is obviously weakened after Hg2+ uptake, which makes the hypercrosslinked conjugated microporous polymer a promising fluorescent probe for Hg2+ detection, owning a super‐high sensitivity (detection limit 5 × 10−8 mol L−1).