A miniature (2.5 cm length × 2.0 cm width × 1.0 cm height), low power (<10 W), and capillary liquid electrode microplasma optical emission spectrometer was developed for rapid determination of metallic species in aqueous solutions. The sample solution can be automatically introduced into the source without a pump owing to the inherent capillary attraction and the force arising from the solution vaporization induced by microplasma. A droplet array was used as a sampling platform to realize flow injection without using any valve and pump, significantly increasing throughput to 90 samples h–1. Sample volume is controlled through the sampling time and reduced to the nanoliter level. With a sampling time of 10 s (equal to 600 nL), detection limits of 30 μg L–1 (18 pg) and 75 μg L–1 (45 pg) were obtained for Cd and Hg, respectively, comparable to those reported for liquid electrode microplasma optical emission spectrometry. However, sample consumption is reduced more than 100-fold, making the proposed technique more suitable for the analysis of elements such as Cd, Hg, Li, Na, and K when sample volumes may be limited. The utility of this system was demonstrated by the determination of Cd and Hg in blood, real water samples, and Certified Reference Materials (rice powder, GBW07601a, and lobster hepatopancreas, TORT-3).

Sensitive quantification of mercury distribution in fish is challenging because of insufficient sensitivities of conventional analytical methods, the limited mass of organs (tens of micrograms to several milligrams), and dilution of analyte concentration from sample digestion. In this work, a simple and robust approach coupling multiwall carbon nanotubes assisted matrix solid-phase dispersion (MWCNTs-MSPD) to single-drop solution electrode glow discharge-induced cold vapor generation (SD-SEGD-CVG) was developed for the sensitive determination of mercury in limited amount of sample. Mercury species contained in a limited amount of sample can be efficiently extracted into a 100 μL of eluent by MWCNTs-MSPD, which are conveniently converted to Hg0 by SD-SEGD-CVG and further transported to atomic fluorescence spectrometry for their determination. Therefore, analyte dilution resulted from sample preparation is avoided and sensitivity is significantly improved. On the basis of consumption of 1 mg of sample, a limit of detection of 0.01 μg L–1 (0.2 pg) was obtained with relative standard deviations (RSDs) of 5.2% and 4.6% for 2 and 20 μg L–1, respectively. The accuracy of the proposed method was validated by analysis of three Certified Reference Materials with satisfying results. To confirm that SD-SEGD-CVG-AFS coupling to MWCNTs-MSPD is a promising method to quantify mercury distribution in fish, this method was successfully applied for the sensitive determination of mercury in seven organs of common carps (muscle, gill, intestine, liver, gallbladder, brain, and eye) after dietary of mercury species. The proposed method provides advantages of minimum sample dilution, low blank, high sample introduction efficiency, high sensitivity, and minimum toxic chemicals and sample consumption.

A new detection system consisted of a flame ionization detector (FID) and a sulfur chemiluminescence detector (SCD) was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography. In this system, sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO2, CO2 and H2O, respectively. The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO2 could be reduced to SO and reacted with O3 to produce characteristic chemiluminescence. Therefore, the chemiluminescence of CO found in conventional SCD were eliminated because CO2 could not be reduced to CO under these conditions. The experimental parameters were systematically investigated. Limit of detection obtained by the proposed system is better than 0.5 μmol/mol for total sulfur and superior to those previously reported. The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including no hydrocarbon interference, better stability, and easier calculation. The utility of this technique was demonstrated by the determination of total sulfur in real samples and two certified reference materials (GBW 06332 and GBW (E) 061320).Download high-res image (87KB)Download full-size imageA new detection system consisted of a flame ionization detector (FID) and a sulfur chemiluminescence detector (SCD) was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography.

There is an urgent need for active and cost-effective catalysts for electrochemical hydrogen evolution reactions to solve global energy issues. In this study, we report the development of interconnected urchin-like cobalt phosphide microspheres film on Ti foil (u-CoP/Ti) as a monolithic hydrogen-evolving catalyst electrode with high activity and strong durability under acidic and alkaline conditions. It affords 10 mA cm−2 at overpotentials as low as 45 mV with the maintenance of its catalytic activity for at least 15 h in 0.5 M H2SO4, outperforming all reported CoP catalysts. When operated in 1.0 M KOH, u-CoP/Ti is also highly active and demands overpotential of 60 mV to drive 10 mA cm−2 with strong durability.

A low-cost, simple, and highly selective analytical method was developed for sensitive visual detection of selenium in human urine both outdoors and at home, by coupling hydride generation with headspace solid-phase extraction using quantum dots (QDs) immobilized on paper. The visible fluorescence from the CdTe QDs immobilized on paper was quenched by H2Se from hydride generation reaction and headspace solid-phase extraction. The potential mechanism was investigated by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) as well as Density Functional Theory (DFT). Potential interferences from coexisting ions, particularly Ag+, Cu2+, and Zn2+, were eliminated. The selectivity was significantly increased because the selenium hydride was effectively separated from sample matrices by hydride generation. Moreover, due to the high sampling efficiency of hydride generation and headspace solid phase extraction, the sensitivity and the limit of detection (LOD) were significantly improved compared to conventional methods. A LOD of 0.1 μg L–1 and a relative standard deviation (RSD, n = 7) of 2.4% at a concentration of 20 μg L–1 were obtained when using a commercial spectrofluorometer as the detector. Furthermore, a visual assay based on the proposed method was developed for the detection of Se, 5 μg L–1 of selenium in urine can be discriminated from the blank solution with the naked eye. The proposed method was validated by analysis of certified reference materials and human urine samples with satisfactory results.

Based on selective and sensitive determination of Hg2+ released from mercury complex by cold vapor generation (CVG) atomic fluorescence spectrometry (AFS) using SnCl2 as a reductant, a novel label-free and separation-free strategy was proposed for DNA and protein bioassay. To construct the DNA bioassay platform, an Hg2+-mediated molecular beacon (hairpin) without labeling but possessing several thymine (T) bases at both ends was employed as the probe. It is well-known that Hg2+ could trigger the formation of the hairpin structure through T–Hg2+–T connection. In the presence of a specific target, the hairpin structure could be broken and the captured Hg2+ was released. Interestingly, it was found that SnCl2 could selectively reduce only free Hg2+ to Hg0 vapor in the presence of T–Hg2+–T complex, which could be separated from sample matrices for sensitive AFS detection. Three different types of analyte, namely, single-strand DNA (ssDNA), protein, and double-strand DNA (dsDNA), were investigated as the target analytes. Under the optimized conditions, this bioassay provided high sensitivity for ssDNA, protein, and dsDNA determination with the limits of detection as low as 0.2, 0.08, and 0.3 nM and the linear dynamic ranges of 10–150, 5–175, and 1–250 nM, respectively. The analytical performance for these analytes compares favorably with those by previously reported methods, demonstrating the potential usefulness and versatility of this new AFS-based bioassay. Moreover, the bioassay retains advantages of simplicity, cost-effectiveness, and sensitivity compared to most of the conventional methods.

Rice consumption is a primary pathway for human methylmercury (MeHg) exposure in inland mercury mining areas of Asia. In addition, the use of iodomethane, a common fumigant that significantly accelerates the methylation of mercury in soil under sunlight, could increase the MeHg exposure from rice. Conventional hyphenated techniques used for mercury speciation analysis are usually too costly for most developing countries. Consequently, there is an increased interest in the development of sensitive and inexpensive methods for the speciation of mercury in rice. In this work, gas chromatography (GC) coupled to dielectric barrier discharge optical emission spectrometry (DBD-OES) was developed for the speciation analysis of mercury in rice. Prior to GC-DBD-OES analysis, mercury species were derivatized to their volatile species with NaBPh4 and preconcentrated by headspace solid phase microextraction using porous carbons. Limits of detection of 0.5 μg kg–1 (0.16 ng), 0.75 μg kg–1 (0.24 ng), and 1.0 μg kg–1 (0.34 ng) were obtained for Hg2+, CH3Hg+, and CH3CH2Hg+, respectively, with relative standard deviations (RSDs) better than 5.2% and 6.8% for one fiber or fiber-to-fiber mode, respectively. Recoveries of 90–105% were obtained for the rice samples, demonstrating the applicability of the proposed technique. Owing to the small size, low power, and low gas consumption of DBD-OES as well as efficient extraction of mercury species by porous carbons headspace solid phase micro-extraction, the proposed technique provides several advantages including compactness, cost-effectiveness, and potential to couple with miniature GC to accomplish the field speciation of mercury in rice compared to conventional hyphenated techniques.

It was found that a capillary electrophoresis (CE) process can be induced by starting a low-temperature d.c. liquid-electrode glow discharge (GD). A novel capillary microplasma analytical system (C-μPAS) was constructed by interface-free coupling of d.c. glow discharge optical emission spectrometry (GD-OES) to CE and was applied in elemental (speciation) analysis. A GD was generated at one end of a capillary, and initiated not only a capillary electrophoresis process but also a microplasma; a sample was injected at the other end of the capillary, separated by CE, and detected by GD-OES. This portable C-μPAS integrates introduction of the sample, separation of the analyte species, and detection of the analytical signal into one unit. The performance of this new analytical system was first evaluated by the analysis of a mixed aqueous solution of mercury, cadmium, chromium, sodium and organic or inorganic species without derivatization, and the absolute limits of detection (LODs) were found to be in the range of 0.5 to 500 picograms under the optimized experimental conditions. Preliminary experimental results for mercury speciation showed that it provided effective separation and results as accurate as those obtained by HPLC-ICP-MS. The working mechanism of this system is discussed, with the theoretically calculated electron temperature and electron density of the microplasma. This C-μPAS has the advantages of portable instrumentation, green chemistry (low power consumption, tiny sampling volume and almost no pollutants), high sensitivity (detection of optical emissions), low interference (separation by CE and spectral resolution), versatility (organic, inorganic, cationic or anionic analytes), and fast analysis (several minutes). It should have a very promising future in a range of areas such as environmental analysis, metallomics research, water analysis, online monitoring and field analytical chemistry.

•Photochemical vapor generation is used for mercury removal from polluted water.•Photo-oxidation is used for trapping the removed mercury onto a quartz tube.•An atomic fluorescence spectrometer is used for sensitive on-line monitoring.•It could be useful in treating slightly mercury-polluted water for drinking in the field.A new system was constructed and its performance evaluated for simultaneous mercury removal from water and on-line monitoring. The system consisted of a photochemical vapor generator (Photo-CVG, for mercury removal), a photo-oxidation trapping reactor (for collection of removed mercury) and a commercial atomic fluorescence spectrometer (AFS, for on-line monitoring). In the presence of organic acids, inorganic Hg(II) was converted by UV irradiation to mercury cold vapor in the Photo-CVG, which was then rapidly separated from the water sample in a gas-liquid separator (GLS) and transported to the photo-oxidation trapping reactor by air or argon for collection of the removed mercury and subsequent on-line monitoring by AFS for early-warning of mercury vapor leak to the environment. The factors affecting the efficiencies of cold vapor generation, transport, collection and on-line monitoring were carefully investigated. Under the optimized conditions, a limit of detection of 0.003 μg L− 1 was obtained for the proposed system by using only formic acid. Meanwhile, both the efficiencies of mercury removal and collection can be even close to 100% in the mercury concentration range of 2–100 μg L− 1. The proposed system provided a safe, green, complete, simple and fast yet inexpensive method for low concentration mercury removal and on-line monitoring.

An environmentally friendly and fast sample treatment approach that integrates accelerated microwave digestion (MWD), solid phase extraction, and magnetic separation into a single step was developed for the determination of arsenic and antimony in fish samples by using Fe3O4 magnetic nanoparticles (MNPs). Compared to conventional microwave digestion, the consumption of HNO3 was reduced significantly to 12.5%, and the digestion time and temperature were substantially decreased to 6 min and 80 °C, respectively. This is largely attributed to Fe3O4 magnetic nanoparticles being a highly effective catalyst for rapid generation of oxidative radicals from H2O2, as well as an excellent absorber of microwave irradiation. Moreover, potential interferences from sample matrices were eliminated because the As and Sb species adsorbed on the nanoparticles were efficiently separated from the digests with a hand-held magnet prior to analysis. Limits of detection for arsenic and antimony were in the range of 0.01–0.06 μg g–1 and 0.03–0.08 μg g–1 by using hydride generation atomic fluorescence spectrometry, respectively, and further improved to 0.002–0.005 μg g–1 and 0.005–0.01 μg g–1 when inductively coupled plasma mass spectrometry was used as a detector. The precision of replicate measurements (n = 9) was better than 6% by analyzing 0.1 g test sample spiked with 1 μg g–1 arsenic and antimony. The proposed method was validated by analysis of two certified reference materials (DORM-3 and DORM-4) with good recoveries (90%–106%).

To evaluate the toxicity of silver nanoparticles (AgNPs) and Ag+ and gain deep insight into the transformation of AgNPs in the environment or organisms, ultrasensitive analytical methods are needed for their speciation analysis. About 40-fold of Cd2+ in CdTe ionic nanocrystals can be “bombarded-and-exploded” (exchanged) in less than 1 min simply by mixing the nanocrystals with Ag+ solution at room temperature, while this cation exchange reaction did not occur when only silver nanoparticles were present. On the basis of this striking difference, an ultrasensitive method was developed for speciation analysis of Ag+ and AgNPs in complex matrices. The released Cd2+ was reduced to its volatile species by sodium tetrahydroborate, which was separated and swept to an inductively coupled plasma mass spectrometer (ICPMS) or an atomic fluorescence spectrometer (AFS) for the indirect but ultrasensitive detection of Ag+. Owing to the remarkable signal amplification via the cation exchange reaction and the advantages of chemical vapor generation for sampling, the limit of detection was 0.0003 μg L–1 for Ag+ by ICPMS, which was improved by 100-fold compared to the conventional method. Relative standard deviations are better than 2.5% at a concentration of 0.5 μg L–1 Ag+ or AgNPs regardless of the detector. The proposed method retains several unique advantages, including ultrahigh sensitivity, speciation analysis, simplicity and being organic reagent-free, and has been successfully utilized for speciation analysis of Ag+ and AgNPs in environmental water samples and paramecium cells.

A compact and robust OES technique was developed for the sensitive determination of Hg, Fe, Ni, and Co by utilizing photochemical vapor generation and point discharge as the sampling technique and the excitation source, respectively. Mercury cold vapor and the volatile species of Fe, Ni, and Co were generated when standard or sample solutions containing formic acid were exposed to a UV photochemical reactor and subsequently separated from the liquid phase for transport to the microplasma and detection of their atomic emission. Limits of detection (LODs) of 0.10, 10, 0.20, and 4.5 μg L–1 were obtained for Hg, Fe, Ni and Co, respectively. Compared to conventional microplasma OES, this method not only broadens the scope of elements amenable to determination, but also provides 2- and 7-fold improvement in the LODs for Hg and Ni, respectively. Method validation was demonstrated by analysis of three Certified Reference Materials (GBW08607, DORM-3, and DORM-4) with satisfactory results, and by good spike recoveries (93–111%) from three real water samples.

The integrity of chemical species throughout the analytical procedure and sample throughput are usually two serious impediments in elemental speciation. In this work, a simple solid sampling platform using multi-wall carbon nanotubes (MWCNTs) assisted matrix solid phase dispersion (MSPD) was constructed for online coupling to high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for the high accuracy and sample throughput mercury speciation in fish samples. Owing to the large surface area and excellent mechanical strength of MWCNTs, which facilitate a sufficient dispersion of a sample matrix and diffusion of the eluent into the mixture of solid support and fish samples, a fast, efficient and online extraction of mercury species was achieved. Compared to the conventional MSPD and other sample pretreatment methods, the proposed method has several advantages including the integration of extraction, clean-up, separation and determination into one single step to achieve a high sample throughput, eliminating the need for derivatization of the Hg species and/or subsequent purification steps, reduced usage of solid supports, minimized contamination and mild operation conditions. The limits of detection of 9.9 ng g−1 and 8.4 ng g−1 were obtained for Hg2+ and CH3Hg+, respectively, based on 1 mg of fish sample. The accuracy of the proposed method was validated by analyzing two certified reference materials. The proposed method was applied for two fresh fish samples for Hg speciation.

It was found that carbon atomic emission can be excited in low temperature dielectric barrier discharge (DBD), and an atmospheric pressure, low power consumption, and compact microplasma carbon atomic emission spectrometer (AES) was constructed and used as a universal and sensitive gas chromatographic (GC) detector for detection of volatile carbon-containing compounds. A concentric DBD device was housed in a heating box to increase the plasma operation temperature to 300 °C to intensify carbon atomic emission at 193.0 nm. Carbon-containing compounds directly injected or eluted from GC can be decomposed, atomized, and excited in this heated DBD for carbon atomic emission. The performance of this new optical detector was first evaluated by determination of a series of volatile carbon-containing compounds including formaldehyde, ethyl acetate, methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol, and absolute limits of detection (LODs) were found at a range of 0.12–0.28 ng under the optimized conditions. Preliminary experimental results showed that it provided slightly higher LODs than those obtained by GC with a flame ionization detector (FID). Furthermore, it is a new universal GC detector for volatile carbon-containing compounds that even includes those compounds which are difficult to detect by FID, such as HCHO, CO, and CO2. Meanwhile, hydrogen gas used in conventional techniques was eliminated; and molecular optical emission detection can also be performed with this GC detector for multichannel analysis to improve resolution of overlapped chromatographic peaks of complex mixtures.

It is critically important to accurately determine histidine since it is an indicator for many diseases when at an abnormal level. Here, an inexpensive and simple method using an amine-functionalized magnetic nanoparticle-based Ni2+–histidine affinity pair system was developed for highly sensitive and selective detection of histidine in human urine by photochemical vapor generation atomic spectrometry. Ni2+ was first bound to the amine groups of the amine-functionalized magnetic nanoparticles and then liberated to solution via the highly specific interaction between the histidine and Ni2+ in the presence of histidine. The liberated histidine–Ni2+ complex was exposed to UV irradiation in the presence of formic acid to form gaseous nickel tetracarbonyl, which was separated from the sample matrix and determined by atomic absorption/fluorescence spectrometry. Compared to other methods, this approach promises high sensitivity, simplicity in design, and convenient operation. The need for organic solvents, enzymatic reactions, separation processes, chemical modification, expensive instrumentations, and sophisticated and complicated pretreatment is minimized with this strategy. A limit of detection of 1 nM was obtained and provided tens-to-hundreds of fold improvements over that achieved with conventional methods. The protocol was evaluated by analysis of several urine samples with good recoveries and showed great potential for practical application.

Because of its unique properties and capability of formation of well-dispersed aqueous colloids in aqueous phase, graphene oxide can be used for the efficient preconcentration of heavy metal ions prior to their determination. The complete collection of graphene oxide colloids from water has generally been considered to be insurmountable. Here, graphene oxide aggregation triggered by introducing NaCl was used to develop a novel organic solvent-free cloud point extraction-like method for the determination of trace toxic metals. The graphene oxide sheets were uniformly dispersed in aqueous samples or standard solutions for a fast and efficient adsorption of Pb(II), Cd(II), Bi(III), and Sb(III) owing to its hydrophilic character and the electrostatic repulsion among the graphene oxide sheets, and its aggregation immediately occurred when the electrostatic repulsion was eliminated via adding NaCl to neutralize the excessive negative charges on the surface of graphene oxide sheets. The aggregates of graphene oxide and analytes ions were separated and treated with hydrochloric acid to form a slurry solution. The slurry solution was pumped to mix with KBH4 solution to generate hydrides, which were subsequently separated from the liquid phase and directed to an atomic fluorescence spectrometer or directly introduced to an inductively coupled plasma optical emission spectrometer for detection. On the basis of a 50 mL sample volume, the limits of detection of 0.01, 0.002, 0.01, and 0.006 ng mL–1 were obtained for Pb, Cd, Bi, and Sb, respectively, when using atomic fluorescence spectrometry, providing 35-, 8-, 36-, and 37-fold improvements over the conventional method. Detection limits of 0.6, 0.15, 0.1, and 1.0 ng mL–1 were obtained with the use of slurry sampling inductively coupled plasma optical emission spectrometry. The method was applied for analysis of two Certified Reference Materials and three water samples for these elements.

A simple and sensitive approach is proposed and evaluated for determination of ultratrace Zn and Cd in limited amounts of samples or tens of cells based on a novel single drop (5–20 μL) solution electrode glow discharge assisted-chemical vapor generation technique. Volatile species of Zn and Cd were immediately generated and separated from the liquid phase for transporting to atomic fluorescence or atomic mass spectrometric detectors for their determination only using hydrogen when the glow discharge was ignited between the surface of a liquid drop and the tip of a tungsten electrode. Limits of detection are better than 0.01 μg L–1 (0.2 pg) for Cd and 0.1 μg L–1 (2 pg) for Zn, respectively, and comparable or better than the previously reported results due to only a 20 μL sampling volume required, which makes the proposed technique convenient for the determination of Zn and Cd in limited amounts of samples or even only tens of cells. The proposed method not only retains the advantages of conventional chemical vapor generation but also provides several unique advantages, including better sensitivity, lower sample and power consumption, higher chemical vapor generation efficiencies and simpler setup, as well as greener analytical chemistry. The utility of this technique was demonstrated by the determination of ultratrace Cd and Zn in several single human hair samples, Certified Reference Materials GBW07601a (human hair powder) and paramecium cells.

A simple, rapid, and portable system consisted of a laboratory-built miniaturized dielectric barrier discharge atomic emission spectrometer and a microwave-assisted persulfate oxidation reactor was developed for sensitive flow injection analysis or continuous monitoring of total organic carbon (TOC) in environmental water samples. The standard/sample solution together with persulfate was pumped to the reactor to convert organic compounds to CO2, which was separated from liquid phase and transported to the spectrometer for detection of the elemental specific carbon atomic emission at 193.0 nm. The experimental parameters were systematically investigated. A limit of detection of 0.01 mg L–1 (as C) was obtained based on a 10 mL sample injection volume, and the precision was better than 6.5% (relative standard deviation, RSD) at 0.1 mg L–1. The system was successfully applied for TOC analysis of real environmental water samples. The obtained TOC value of 30 test samples agreed well with those by the standard high-temperature combustion coupled nondispersive infrared absorption method. Most importantly, the system showed good capability of in situ continuous monitoring of total organic carbon in environmental water.

A dual-mode chemical vapor generation integrating hydride generation and photochemical vapor generation was developed for simultaneous multi-element analysis of hydride-forming and non-hydride-forming elements by atomic fluorescence spectrometry. Four elements were selected as model elements of hydride-forming (As, Cd) and non-hydride-forming (Ni, Fe) elements to validate this proposed method. Standard or sample solutions were separately pumped to mix with tetrahydroborate, and concentrated formic acid and ammonia, and then directed to a hydride generator and a photochemical reactor to realize simultaneous hydride generation and photochemical vapor generation, respectively. Optimum conditions for dual-mode chemical vapor generation were carefully investigated. Under the optimized conditions, limits of detection of 0.05, 0.008, 0.8 and 0.1 μg L−1 were obtained for As, Cd, Fe and Ni, respectively. The precisions were 5.0, 5.5, 4.3 and 4.5% (n = 6, RSDs) for 2 μg L−1 of As, 1 μg L−1 of Cd, 50 μg L−1 of Fe and 10 μg L−1 of Ni, respectively. This method was validated for accuracy with three certified reference water samples and applied to the simultaneous determination of these elements in a tap water sample with spike recoveries in the range of 95–99%.

An in-atomizer atom trapping method based on coating gold nanoparticles onto the inner wall of a quartz tube atomizer was firstly developed and combined with flow injection cold vapor generation for the accurate determination of mercury at low μg L−1 levels by atomic absorption spectrometry. Mercury vapor generated by reducing Hg2+ with hydrochloric acid–tetrahydroborate was efficiently trapped on the surface of gold nanoparticles that were coated on the interior wall of the quartz tube atomizer prior to the determination. In situ desorption and determination of mercury was achieved by increasing the voltage (thus the temperature) to 30 V. The influence of instrumental parameters and experimental conditions on the generation, trapping and desorption of mercury vapor, as well as interference from concomitant elemental ions was investigated. A detection limit of 0.01 μg L−1 was obtained based on a 5.0 mL sampling volume. The precision was better than 4.0% at 0.5 μg L−1. Three spiked water samples and two Certified Reference Materials (dogfish muscle, DORM-4 and human hair powder GBW07601a) were analyzed to validate the accuracy of the proposed method.

•A tungsten-coil was used as a trapping device and atomizer for cadmium volatile species.•Hydride generation was used for producing cadmium volatile species.•Cadmium atomic absorption was measured with a portable atomic absorption spectrometer.•Flow injection was used for high sample throughput.•The method is simple, fast and highly sensitive.Here we report the use of the tungsten-coil atomizer of a portable atomic absorption spectrometer as an on-atomizer trapping device and atomizer for the determination of trace cadmium, with flow injection hydride generation for production of volatile cadmium species from sample solutions. By mixing acidic analyte solution with tetrahydroborate solution, volatile cadmium species is produced and separated from the solution, and then transported and impacted onto the surface of the atomizer with a heating current set at 2.3 A. Subsequent atomic absorption measurement was accomplished with in situ atomization at 8.5 A. Compared to conventional direct injection, the sensitivity and the limit of detection were improved by 58- and 66-fold, respectively, based on 5.0 mL sampling volume. In addition, use of flow injection significantly improved sample throughput. The proposed method was used for the analysis of several real water samples with good spiked recoveries.

A UV Fenton-like digestion method was developed first time for a complete digestion of milk samples by using 1.6 g L–1 Fe3O4 magnetic nanoparticles, 0.2% (v/v) nitric acid, and 6% (w/w) H2O2. During the digestion, the liberated As-, Sb-, and Bi-containing species were preconcentrated onto the surface of Fe3O4 magnetic nanoparticles, which were conveniently separated with a hand-held magnet and subsequently dissolved in hydrochloric acid prior to hydride generation atomic fluorescence spectrometric detection. Owing to the integration of UV Fenton-like digestion, solid phase extraction, and magnetic separation into a single step, the developed method significantly simplifies sample preparation steps and reduces chemical consumption and hazardous waste. Limits of detection of 0.0015, 0.0022, and 0.0025 μg L–1 were obtained for As, Sb, and Bi, respectively, using a 50 mL milk sample. The method was applied to the determination of these elements in a Certified Reference Material and milk samples.

An improved hollow fiber supported liquid–liquid–liquid membrane microextraction (HF-LLLMME) method is described for the simultaneous extraction of inorganic and organic mercury species with high efficiency prior to speciation analysis by capillary electrophoresis. The HF-LLLMME was developed by filling cyclohexane and L-cysteine aqueous solution in the pores of the hollow fiber wall and its lumen as organic liquid membrane and acceptor phase, respectively. Inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) firstly formed hydrophobic complexes with 1-(2-pyridylazo)-2-naphthol in donor solutions, wherein the hollow fiber was immersed. The complexes were then extracted into the organic liquid membrane and further transferred into the lumen of the hollow fiber to form hydrophilic complexes with L-cysteine. The factors affecting the extraction efficiency were carefully investigated. With the consumption of 50 mL of sample solution, the enrichment factor was 103, 265, 511 and 683 for Hg2+, MeHg, EtHg and PhHg, respectively. The limits of detection were in the range of 0.07–1.0 ng mL−1 (as Hg) with precisions (RSDs, n = 6) ranging from 1.7 to 4.4%. The proposed method was validated by analyzing a certified reference material (DORM-2, dogfish-muscle) and an environmental water sample with satisfactory results.

A new, miniaturized and low power consumption photochemical vapor generation (PVG) technique utilizing an ultraviolet light-emitting diode (UV-LED) lamp is described, and further validated via the determination of trace mercury. In the presence of formic acid, the mercury cold vapor is favourably generated from Hg2+ solutions by UV-LED irradiation, and then rapidly transported to an atomic fluorescence spectrometer for detection. Optimum conditions for PVG and interferences from concomitant elements were investigated in detail. Under optimum conditions, a limit of detection (LOD) of 0.01 μg L−1 was obtained, and the precision was better than 3.2% (n = 11, RSD) at 1 μg L−1Hg2+. No obvious interferences from any common ions were evident. The methodology was successfully applied to the determination of mercury in National Research Council Canada DORM-3 fish muscle tissue and several water samples.

An ultrasensitive, simple and interference-free method using nano-TiO2 preconcentration and in situ slurry hydride generation (HG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of trace selenium. Total Se reduced in Se(IV) form can be selectively adsorbed on TiO2 at pH < 8 for pre-concentration, and then separated and slurried/released by a mixture containing 3% (m/v) KBH4 and 1% (m/v) KOH. The slurry solution was mixed with 25% (v/v) HCl to generate selenium hydrides, which was subsequently separated from the liquid phase for subsequent AFS detection. Optimum conditions for adsorption, disadsorption and hydride generation of selenium as well as potential interferences from concomitant ions were investigated. Due to the repulsive force between the positively charged TiO2 and metal cationic ions, this approach permits 1000 mg L−1 for Fe3+, Ni2+ and Co2+, 500 mg L−1 for Cu2+ or 100 mg L−1 for Ag+ and Au3+ present in a 5 μg L−1Se(IV) solution without any significant interferences. A limit of detection of 0.0006 μg L−1 was obtained by sampling a 40 mL sample solution. Compared to the conventional HG method, the sensitivity and the limit of detection were improved 17- and 16-fold by the present method, respectively. The proposed method was successfully applied for the determination of trace selenium in several real samples.

A novel compact tandem atomizer is described and evaluated for its analytical performance using atomic fluorescence spectrometry (AFS). The atomizer simply comprises an argon–hydrogen (Ar–H2) flame atomizer and an electrothermal atomization/vaporization (ETV) sampling device, which utilizes a tungsten coil (W-coil) onto which a liquid sample is pipetted, and subsequently the analyte is electrothermally atomized/vaporized and swept directly into the highly reducing environment of the Ar–H2 flame atomizer for further atomization and detection. The flame sits directly on top of the W-coil without any interface tubing. Improvements in elemental coverage, sensitivity and minimization of analyte loss as well as reduction of reagent consumption were simultaneously achieved by the use of this technique. The absolute limits of detection (LODs) are comparable to those obtained by GF-AAS but provide significant improvements over FAAS and ICP-OES. Its application example was demonstrated by analyzing several Certified Reference Materials and environmental water samples for ultratrace Cd, Pb, Au and Ag.

A new efficient method was described for the purification of K3[Fe(CN)6] for the purpose of minimization of the blank in the determination of trace lead by hydride generation-atomic fluorescence spectrometry using the HCl–K3[Fe(CN)6]–KBH4 system. The lead impurity in K3[Fe(CN)6] solution was removed by reacting with KBH4 to form PbH4, which was efficiently separated from the solution by a nitrogen gas flow. The purified K3[Fe(CN)6] was obtained via Cl2 oxidation and subsequent ethanol purification of its reduced compound. The optimum conditions for hydride generation of lead and purification of K3[Fe(CN)6] were carefully investigated. A limit of detection (LOD) of 0.05 μg L−1 was obtained, 100-fold better than that achieved with unpurified K3[Fe(CN)6]. The accuracy of the proposed method was validated by analyzing a Certified Reference hair sample (GBW07610) and two ore samples (GBW07106 and GBW07112) with satisfactory analytical results.

A new and simple cold vapor generation technique utilizing microwave irradiation coupled with atomic fluorescence spectrometry is developed for the speciation analysis of mercury in biological and geological samples. In the presence of formic acid, inorganic mercury (Hg2+) and total mercury (both Hg2+ and methylmercury (MeHg)) can be converted to mercury cold vapor (Hg0) by microwave irradiation without and with H2O2, respectively. The cold vapor was subsequently released from the liquid phase and rapidly transported to an atomic fluorescence spectrometer for the mercury detection. Optimum conditions for vapor generation as well as interferences from concomitant ions were carefully investigated. The conventionally required evaporation of the remnants of acid or oxidants was avoided because no significant interferences from these substances were observed, and thus analyte loss and potential contamination were minimized. A limit of detection of 0.005 ng mL−1 for total mercury or inorganic mercury was obtained. A precision of less than 3% (RSD) at 2 μg L−1 of mercury species was typical. The accuracy of the method was validated by determination of mercury in geological and biological certified reference materials. The speciation analysis of Hg2+ and MeHg was achieved by controlling the conditions of microwave-enhanced cold vapor generation and validated via determination of Certified Reference Materials DORM-2, DORM-3 and a real river water sample.Highlights► A simple and novel cold vapor generation method utilizing only formic acid with microwave irradiation. ► Non chromatographic speciation analysis of mercury achieved by controlling experimental conditions. ► The evaporation of the remnants of acid or oxidants was eliminated. ► The LOD was comparable or better than those reported methods.

We have developed a rapid, selective and efficient method for dispersive solid-phase microextraction (DSPME) using microbeads of a molecularly imprinted polymer (MIP). It enables the pre-concentration of sulfamethazine and sample clean-up prior to capillary electrophoresis with UV detection. The microbeads were synthesized via precipitation polymerization using sulfamethazine, methacrylic acid and ethylene glycol dimethacrylate (EGDMA) as the template molecule, the functional monomer and the cross-linking monomer, respectively. Characterization by SEM displayed the high uniformity and dispersibility of the MIP microbeads. The adsorption and desorption of sulfamethazine and the parameters for CE were optimized to result in a limit of detection of 1.1 μg L−1, which is 373-fold lower than that of direct CE detection. The equilibration time of extraction was reduced to 5 min, and the selectivity of the microbeads was significantly improved compared to the non-imprinted polymer. The method was successfully applied to the determination of trace sulfamethazine in several milk samples, with recoveries in the range of 89 % to 110 %.

A dielectric barrier discharge (DBD) was used as a new atmospheric optical emission detector for the determination of trace nitrogen in pure argon gas in this work. The whole system was composed of an ac ozone generation device for power supply, a six-way valve, a laboratory-built DBD device and a USB2000 charge coupled device (CCD). Trace nitrogen in argon was detected at nitrogen molecular emission line of 337 nm. This method features with several advantages: atmospheric working condition, low power consumption (≤ 12 W), simple and cheap instrumentation, fast response and high sensitivity and accuracy. Under the optimized conditions, the limits of detection can be down to 34 ppb.

Mercury solution without or with formic acid was introduced into a low temperature argon plasma from dielectric barrier discharge (DBD). Mercury vapor generated in the DBD was separated from the liquid phase and finally swept into an inductively coupled plasma optical emission spectrometer (ICP-OES) for determination. The optimum conditions for the proposed technique and operation of the ICP-OES, as well as interferences from concomitants, were investigated in detail. It was found that the vapor generation efficiency of mercury could be significantly enhanced with the addition of formic acid. However, the efficiency was reduced sharply in the presence of chloride ions or oxidizing substances of high concentration. Under the optimized conditions, a limit of detection of 0.090 μg L−1 and a precision of 2.1% RSD at a concentration of 10 μg L−1 were achieved by the proposed method. The new DBD-induced mercury vapor generation provides several advantages including low power consumption (<25 W), green analytical chemistry, cost-effectiveness, smaller size, long operation lifetime, and ease of on-line operation. The methodology has been successfully applied to the determination of mercury in a certified reference water sample and mineral water samples.

An environmentally friendly, low power consuming, sensitive and compact mercury analyzer was developed for the determination of mercury in water samples by integrating a thin film dielectric barrier discharge induced cold vapor reactor and a dielectric barrier discharge optical emission spectrometer into a small polymethyl methacrylate plate (10.5 cm length × 8.0 cm width × 1.2 cm height). Mercury cold vapor was generated when standard or sample solutions with or without formic acid were introduced to the reactor to form thin film liquid and exposed to microplasma irradiation and subsequently separated from the liquid phase for transport to the microplasma and detection of its atomic emission. Limits of detection of 0.20 μg L−1 and 2.6 μg L−1 were obtained for the proposed system using or not using formic acid, respectively. Compared to the conventional microplasma optical emission spectrometry used for mercury analysis, this system not only retains the good limit of detection amenable to the determination of mercury in real samples, but also reduces power consumption, eliminates the generation of hydrogen and avoids the use of toxic or unstable reductant. Method validation was demonstrated by analysis of a certified reference material of water sample and three real water samples with good spike recoveries (88–102%).A robust and compact mercury analyzer integrating a thin film dielectric barrier discharge induced cold vapor generator and a dielectric barrier discharge optical emission spectrometer was developed for the determination of mercury in water samples.

An ultrasensitive, simple and interference-free method using nano-TiO2 preconcentration and in situ slurry hydride generation (HG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of trace selenium. Total Se reduced in Se(IV) form can be selectively adsorbed on TiO2 at pH < 8 for pre-concentration, and then separated and slurried/released by a mixture containing 3% (m/v) KBH4 and 1% (m/v) KOH. The slurry solution was mixed with 25% (v/v) HCl to generate selenium hydrides, which was subsequently separated from the liquid phase for subsequent AFS detection. Optimum conditions for adsorption, disadsorption and hydride generation of selenium as well as potential interferences from concomitant ions were investigated. Due to the repulsive force between the positively charged TiO2 and metal cationic ions, this approach permits 1000 mg L−1 for Fe3+, Ni2+ and Co2+, 500 mg L−1 for Cu2+ or 100 mg L−1 for Ag+ and Au3+ present in a 5 μg L−1Se(IV) solution without any significant interferences. A limit of detection of 0.0006 μg L−1 was obtained by sampling a 40 mL sample solution. Compared to the conventional HG method, the sensitivity and the limit of detection were improved 17- and 16-fold by the present method, respectively. The proposed method was successfully applied for the determination of trace selenium in several real samples.

An in-atomizer atom trapping method based on coating gold nanoparticles onto the inner wall of a quartz tube atomizer was firstly developed and combined with flow injection cold vapor generation for the accurate determination of mercury at low μg L−1 levels by atomic absorption spectrometry. Mercury vapor generated by reducing Hg2+ with hydrochloric acid–tetrahydroborate was efficiently trapped on the surface of gold nanoparticles that were coated on the interior wall of the quartz tube atomizer prior to the determination. In situ desorption and determination of mercury was achieved by increasing the voltage (thus the temperature) to 30 V. The influence of instrumental parameters and experimental conditions on the generation, trapping and desorption of mercury vapor, as well as interference from concomitant elemental ions was investigated. A detection limit of 0.01 μg L−1 was obtained based on a 5.0 mL sampling volume. The precision was better than 4.0% at 0.5 μg L−1. Three spiked water samples and two Certified Reference Materials (dogfish muscle, DORM-4 and human hair powder GBW07601a) were analyzed to validate the accuracy of the proposed method.

Mercury solution without or with formic acid was introduced into a low temperature argon plasma from dielectric barrier discharge (DBD). Mercury vapor generated in the DBD was separated from the liquid phase and finally swept into an inductively coupled plasma optical emission spectrometer (ICP-OES) for determination. The optimum conditions for the proposed technique and operation of the ICP-OES, as well as interferences from concomitants, were investigated in detail. It was found that the vapor generation efficiency of mercury could be significantly enhanced with the addition of formic acid. However, the efficiency was reduced sharply in the presence of chloride ions or oxidizing substances of high concentration. Under the optimized conditions, a limit of detection of 0.090 μg L−1 and a precision of 2.1% RSD at a concentration of 10 μg L−1 were achieved by the proposed method. The new DBD-induced mercury vapor generation provides several advantages including low power consumption (<25 W), green analytical chemistry, cost-effectiveness, smaller size, long operation lifetime, and ease of on-line operation. The methodology has been successfully applied to the determination of mercury in a certified reference water sample and mineral water samples.

The integrity of chemical species throughout the analytical procedure and sample throughput are usually two serious impediments in elemental speciation. In this work, a simple solid sampling platform using multi-wall carbon nanotubes (MWCNTs) assisted matrix solid phase dispersion (MSPD) was constructed for online coupling to high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for the high accuracy and sample throughput mercury speciation in fish samples. Owing to the large surface area and excellent mechanical strength of MWCNTs, which facilitate a sufficient dispersion of a sample matrix and diffusion of the eluent into the mixture of solid support and fish samples, a fast, efficient and online extraction of mercury species was achieved. Compared to the conventional MSPD and other sample pretreatment methods, the proposed method has several advantages including the integration of extraction, clean-up, separation and determination into one single step to achieve a high sample throughput, eliminating the need for derivatization of the Hg species and/or subsequent purification steps, reduced usage of solid supports, minimized contamination and mild operation conditions. The limits of detection of 9.9 ng g−1 and 8.4 ng g−1 were obtained for Hg2+ and CH3Hg+, respectively, based on 1 mg of fish sample. The accuracy of the proposed method was validated by analyzing two certified reference materials. The proposed method was applied for two fresh fish samples for Hg speciation.

A new efficient method was described for the purification of K3[Fe(CN)6] for the purpose of minimization of the blank in the determination of trace lead by hydride generation-atomic fluorescence spectrometry using the HCl–K3[Fe(CN)6]–KBH4 system. The lead impurity in K3[Fe(CN)6] solution was removed by reacting with KBH4 to form PbH4, which was efficiently separated from the solution by a nitrogen gas flow. The purified K3[Fe(CN)6] was obtained via Cl2 oxidation and subsequent ethanol purification of its reduced compound. The optimum conditions for hydride generation of lead and purification of K3[Fe(CN)6] were carefully investigated. A limit of detection (LOD) of 0.05 μg L−1 was obtained, 100-fold better than that achieved with unpurified K3[Fe(CN)6]. The accuracy of the proposed method was validated by analyzing a Certified Reference hair sample (GBW07610) and two ore samples (GBW07106 and GBW07112) with satisfactory analytical results.

A novel compact tandem atomizer is described and evaluated for its analytical performance using atomic fluorescence spectrometry (AFS). The atomizer simply comprises an argon–hydrogen (Ar–H2) flame atomizer and an electrothermal atomization/vaporization (ETV) sampling device, which utilizes a tungsten coil (W-coil) onto which a liquid sample is pipetted, and subsequently the analyte is electrothermally atomized/vaporized and swept directly into the highly reducing environment of the Ar–H2 flame atomizer for further atomization and detection. The flame sits directly on top of the W-coil without any interface tubing. Improvements in elemental coverage, sensitivity and minimization of analyte loss as well as reduction of reagent consumption were simultaneously achieved by the use of this technique. The absolute limits of detection (LODs) are comparable to those obtained by GF-AAS but provide significant improvements over FAAS and ICP-OES. Its application example was demonstrated by analyzing several Certified Reference Materials and environmental water samples for ultratrace Cd, Pb, Au and Ag.

There is an urgent need for active and cost-effective catalysts for electrochemical hydrogen evolution reactions to solve global energy issues. In this study, we report the development of interconnected urchin-like cobalt phosphide microspheres film on Ti foil (u-CoP/Ti) as a monolithic hydrogen-evolving catalyst electrode with high activity and strong durability under acidic and alkaline conditions. It affords 10 mA cm−2 at overpotentials as low as 45 mV with the maintenance of its catalytic activity for at least 15 h in 0.5 M H2SO4, outperforming all reported CoP catalysts. When operated in 1.0 M KOH, u-CoP/Ti is also highly active and demands overpotential of 60 mV to drive 10 mA cm−2 with strong durability.

An improved hollow fiber supported liquid–liquid–liquid membrane microextraction (HF-LLLMME) method is described for the simultaneous extraction of inorganic and organic mercury species with high efficiency prior to speciation analysis by capillary electrophoresis. The HF-LLLMME was developed by filling cyclohexane and L-cysteine aqueous solution in the pores of the hollow fiber wall and its lumen as organic liquid membrane and acceptor phase, respectively. Inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) firstly formed hydrophobic complexes with 1-(2-pyridylazo)-2-naphthol in donor solutions, wherein the hollow fiber was immersed. The complexes were then extracted into the organic liquid membrane and further transferred into the lumen of the hollow fiber to form hydrophilic complexes with L-cysteine. The factors affecting the extraction efficiency were carefully investigated. With the consumption of 50 mL of sample solution, the enrichment factor was 103, 265, 511 and 683 for Hg2+, MeHg, EtHg and PhHg, respectively. The limits of detection were in the range of 0.07–1.0 ng mL−1 (as Hg) with precisions (RSDs, n = 6) ranging from 1.7 to 4.4%. The proposed method was validated by analyzing a certified reference material (DORM-2, dogfish-muscle) and an environmental water sample with satisfactory results.