Highly Selective and Portable Fluorescence Turn-On Detection of Sc3+ in Ore and Water Based on Strong Lewis Acid-Base Coordination.

Detecting scandium (Sc) with high selectivity and sensitivity is a challenging task due to its chemical similarity to other rare earth ions. Our findings show that the fluorescence of the complex fluorescent indicator calcein (CL) is quenched under acidic conditions (pH = 2), and Sc3+ strongly inhibits this process. The results demonstrate that CL forms multimers and precipitates out of the solution under acidic conditions, while Sc3+ causes a significant decrease in the scattering intensity of the solution. Additional experiments revealed that the strong Lewis acid nature of Sc3+ complexes with the carboxyl groups of CL leads to increased dispersion of CL even under acidic conditions, thus enhancing its absorption and fluorescence. The complexation ratio of Sc3+ and CL was investigated through spectral titrations and theoretical calculations. The interaction between Sc3+ and CL is the strongest among rare earth and common metal ions due to the smallest ionic radius, resulting in high selectivity. The fluorescence turn-on strategy had a linear range of 0.04 to 2.25 µM under optimal conditions, with a detection limit of 20 nM for Sc3+. The combination of 3D printing and a smartphone program allows for portable on-site analysis of Sc3+. Mineral and water samples were used to demonstrate the potential of this strategy for the rapid, selective, and sensitive analysis of low levels of Sc3+.

Machine Learning-Assisted Portable Microplasma Optical Emission Spectrometer for Food Safety Monitoring.

To meet the needs of food safety for simple, rapid, and low-cost analytical methods, a portable device based on a point discharge microplasma optical emission spectrometer (µPD-OES) was combined with machine learning to enable on-site food freshness evaluation and detection of adulteration. The device was integrated with two modular injection units (i.e., headspace solid-phase microextraction and headspace purge) for the examination of various samples. Aromas from meat and coffee were first introduced to the portable device. The aroma molecules were excited to specific atomic and molecular fragments at excited states by room temperature and atmospheric pressure microplasma due to their different atoms and molecular structures. Subsequently, different aromatic molecules obtained their own specific molecular and atomic emission spectra. With the help of machine learning, the portable device was successfully applied to the assessment of meat freshness with accuracies of 96.0, 98.7, and 94.7% for beef, pork, and chicken meat, respectively, through optical emission patterns of the aroma at different storage times. Furthermore, the developed procedures can identify beef samples containing different amounts of duck meat with an accuracy of 99.5% and classify two coffee species without errors, demonstrating the great potential of their application in the discrimination of food adulteration. The combination of machine learning and µPD-OES provides a simple, portable, and cost-effective strategy for food aroma analysis, potentially addressing field monitoring of food safety.

Dried Blood Spots and Miniaturized Ultrasonic Nebulization Microplasma Optical Emission Spectrometry for Point-of-Care Testing of Blood Lithium.

Despite the significant importance of blood lithium (Li) detection in the treatment of bipolar disorder (BD), its point-of-care testing (POCT) remains a great challenge due to tedious sample preparation and the use of large-footprint atomic spectrometers. Herein, a system coupling dried blood spots (DBS) with a point discharge optical emission spectrometer equipped with a miniaturized ultrasonic nebulizer (MUN-µPD-OES) was developed for POCT of blood Li. Three microliters of whole blood were used to prepare a dried blood spot on a piece of filter paper to which 10 µL of eluent (1% (v/v) formic acid and 0.05% (v/v) Triton-X) was added. Subsequently, the paper was placed onto the vibrating steel membrane of the ultrasonic nebulizer and powered on to generate aerosol. The aerosol was directly introduced to the µPD-OES for quantification of Li by monitoring its atomic emission line at 670.8 nm. The proposed method minimized matrix interference caused by high levels of salts and protein. It is worth noting that the MUN suitably matches the needs of DBS sampling and can provide aerosolized introduction of Li into the assembled µPD-OES, thus eliminating all tedious sample preparation and the need for a commercial atomic spectrometer. Calibration response is linear in the therapeutic range and a limit of detection (LOD) of 1.3 µg L-1 is well below the Li minimum therapeutic concentration (2800 µg L-1). Li in mouse blood was successfully detected in real-time using MUN-µPD-OES after intraperitoneal injection of lithium carbonate, confirming that the system holds great potential for POCT of blood Li for patients with BD.

Field Detection of Uranyl in Coastal Water of China Using a Portable Device via DNA Photocleavage.

The urgent need for field detection of uranium in seawater is 2-fold: to provide prompt guidance for uranium extraction and to prevent human exposure to nuclear radiation. However, current methods for this purpose are largely hindered by bulky instrumentation, high costs of developed materials, and severe matrix interferences, which limit their further application in the field. Herein, we demonstrated a portable and label-free strategy for the field detection of uranyl in seawater based on the efficient photocleavage of DNA. Further experiments confirmed the generation of ultraviolet (UV) light-induced reactive oxygen species (ROS), such as O2•- and •OH, which fragmented oligomeric DNA in the presence of uranyl and UV light. Detailed studies showed that DNA significantly enhances uranyl absorption in the UV-visible region, leading to the generation of more ROS. A fluorescence system for the selective detection of uranyl in seawater was established by immobilizing two complementary oligonucleotides with the fluorescent dye SYBR Green I. The strategy of UV-induced photocleavage offers high selectivity, excellent interference immunity, and high sensitivity for uranyl, with a detection limit of 6.8 nM. Additionally, the fluorescence can be visually detected using a 3D-printed miniaturized device integrated with a smartphone. This method has been successfully applied to the on-site detection of uranyl in seawater in 18 Chinese coastal cities and along the coast of Hainan Island within 3 min for a single sample. The sample testing and field analysis results indicate that this strategy has promising potential for real-time monitoring of trace uranyl in China's coastal waters. It is expected to be utilized for the rapid assessment of nuclear contamination and nuclear engineering construction.

Portable Pyrolysis-Point Discharge Optical Spectrometer for In Situ Plastic Polymer Identification by Coupling with Machine Learning.

Rapid and in situ identification of specific polymers is a challenging and crucial step in plastic recycling. However, conventional techniques continue to exhibit significant limitations in the rapid and field classification of plastic products, especially with the wide range of commercially available color polymers because of their large size, high energy consumption, and slow and complicated analysis procedures. In this work, a simple analytical system integrating a miniature and low power consumption (22.3 W) pyrolyzer (Pyr) and a low temperature, atmospheric pressure point discharge optical emission spectrometer (µPD-OES) was fabricated for rapidly identifying polymer types. Plastic debris is decomposed in the portable pyrolyzer to yield volatile products, which are then swept into the µPD-OES instrument for monitoring the optical emission patterns of the thermal pyrolysis products. With machine learning, five extensively used raw polymers and their consumer plastics were classified with an accuracy of ≥97.8%. Furthermore, the proposed method was applied to the identification of the aged polymers and plastic samples collected from a garbage recycling station, indicating its great potential for identification of environmentally weathered plastics. This portable Pyr-µPD-OES system provides a cost-effective tool for rapid and field identification of polymer types of recycled plastic for proper management and resource recycling.

How does psychosocial safety climate cross-level influence work engagement and job burnout: the roles of organization-based self-esteem and psychological detachment.

BACKGROUND: Existing researches on nurses' work engagement and job burnout have mostly stayed at the individual level, and limited researches test the cross-level effects of psychosocial safety climate (PSC). The study aimed to explore the cross-level mediating effect of organization-based self-esteem (OBSE) and the moderating effect of psychological detachment between the relationship of PSC and work engagement and job burnout in nurses. METHODS: The cross-sectional study was conducted during November to December 2022 at a tertiary hospital in a northeastern province of China. Data was collected from 1832 nurses through an online questionnaire. Correlation analyses and hierarchical linear modeling were used to test study hypotheses. RESULTS: The results showed that PSC was positively associated with work engagement, and negatively associated with job burnout. OBSE mediated the effect of PSC on work engagement, as well as job burnout. Additionally, psychological detachment played a moderating role between PSC and work engagement, but no moderating effect was found between PSC and job burnout. CONCLUSIONS: PSC at the organizational level increases work engagement and reduces job burnout by stimulating nurses' high levels of OBSE. Psychological detachment, as a situational factor, enhances the positive influence of PSC on work engagement. The implementation of measures to improve the PSC levels of the organization, and the levels of OBSE and psychological detachment among nurses could help to promote their good work performance.

Solid Phase Photothermo-Induced Chemical Vapor Generation: A New Desorption Method for Mercury Analysis by High-Throughput 20-Fiber Direct Immersion Solid Phase Microextraction.

A simple solid phase photothermo-induced chemical vapor generation (SP-PT-CVG) is described and used as an environmentally friendly desorption method for the sensitive determination of mercury in water by direct immersion solid phase microextraction (DI-SPME) atomic fluorescence spectrometry (AFS). A DI-SPME array equipped with 20 nano-TiO2-coated tungsten fibers was employed to simultaneously preconcentrate mercury from 20 samples, enabling an extraction throughput of 40 samples per hour. Subsequently, the fibers were drawn from the sample solutions and inserted into an inner tube sealed in a specially designed UV lamp in turn for SP-PT-CVG to generate Hg0, which was swept to an AFS detector for its detection. It is worth noting that the tube served as both a vapor generator and a desorption chamber. This proof-of-concept study confirms the feasibility of solid phase CVG. Compared to conventional CVG carried out in the liquid phase, solid phase CVG not only retains the advantages of conventional CVG but also alleviates the matrix interference on vapor generation and preconcentrates analyte prior to vapor generation, improving analytical performance for liquid state samples. DI-SPME-SP-PT-CVG-AFS provides a limit of detection of 2.3 ng L-1 for mercury determination by AFS. In the proposed method, the combination of DI-SPME and SP-PT-CVG eliminates the tedious derivatization steps required in conventional headspace SPME, thus minimizing toxic reagent consumption and improving extraction throughput. The practicality of DI-SPME-SP-PT-CVG-AFS was evaluated by analyzing two different certified reference materials and river water samples with good spike recoveries (98-107%).

Point-of-Care Platform Based on Solid-Phase Fluorescence Filter Effect for Urinary Iodine Testing in Children and Pregnant Women.

Iodine is an essential element that is used to make thyroid hormones. However, people usually ignore their iodine nutrition level, thus leading to a series of thyroid diseases, particularly in areas where medical resources are scarce. Thus, development of a portable, economical, and simple method for the detection of urinary iodine is of significant importance. Herein, a solid-phase fluorescence filter effect (SPFFE) induced by iodine was used to develop an SPFFE-based point-of-care testing (POCT) platform for the detection of urinary iodine by coupling with headspace sample introduction. This method can not only alleviate the matrix interference that occurred in the conventional inner filter effect (IFE) but also achieve high sensitivity. Furthermore, the urinary iodine (UI) POCT platform was developed through the integration of a sample pretreatment and fluorescence readout. This whole system costs less than US $20 and provides accurate temperature control and a portable fluorescence reading within 15-20 min. Compared to the traditional IFE-based assay, the SPFFE-based POCT platform allows the selective detection of iodine as low as 10 nM and has a linear range of 0.05-4 µM. In addition, it provides notable visualization from blue-violet to orange-red in the presence of iodine, which tends to indicate the iodine nutritional status of the human body. Eventually, the clinical applicability and feasibility of the UIPOCT platform as an early diagnostic test kit were confirmed by determining the iodine in urine samples from children and pregnant women.

Automatic and Matrix Interference-Free Acid-Base Titration by Coupling CO2 Vapor Generation with Microplasma Carbon Optical Emission Spectrometry.

Acid-base titration of complex samples is conducive to the rapid evaluation of the degree and risk of environmental pollution to some extent. However, the traditional titration methods usually suffer from serious interference. Herein, an automatic acid-base titration method coupling miniature point discharge optical emission spectrometry (µPD-OES) with CO2 vapor generation was described for the precise, sensitive, and matrix interference-free acid-base titration of complex samples, particularly those with high color intensity, salinity, and turbidity such as wastewater and soil samples. In this work, acid-base titration was carried out in a chemical vapor generator where CO2 was generated through the addition of HCl or NaHCO3, thus enabling efficient separation of CO2 from a complex matrix. The generated CO2 was subsequently swept into the miniaturized point discharge for excitation and further detection by µPD-OES, where the carbon atomic emission at 193.0 nm was monitored. According to the consumed volume and concentration of HCl, accurate and automatic measurements of OH-, CO32-, and HCO3- can be accomplished. The proposed method possesses a high sensitivity of µPD-OES for the detection of CO2 with a relative standard deviation of below 3.0%. Moreover, the proposed system not only retains several unique advantages of accuracy, simplicity, and elimination of the use of complicated, expensive, and high power-consumption instruments but also alleviates the color and turbid interference from complex samples such as dyeing wastewater samples, oilfield water samples, and soil samples. It retains a promising potential application for titration analysis of other samples such as sludge, sediment, and landfill leachate.

Battery-Operated and Self-Heating Solid-Phase Microextraction Device for Field Detection and Long-Term Preservation of Mercury in Soil.

The application of headspace solid-phase microextraction (HS-SPME) for mercury preservation and detection still has several shortcomings, including the use of high-temperature desorption chamber, the consumption of expensive reagent (NaBEt4 or NaBPr4), and analyte loss during sample storage. Herein, a self-heating HS-SPME device using a gold-coated tungsten (Au@W) fiber was developed for the field detection of mercury in soil by miniature point discharge optical emission spectrometry (µPD-OES). Hg2+ was reduced to Hg0 with NaBH4 solution and then preconcentrated with the Au@W fiber. The adsorbed Hg0 could be rapidly desorbed by directly heating the fiber with a mini lithium battery and subsequently detected by µPD-OES. A limit of detection (LOD) of 0.008 mg kg-1 was obtained with a relative standard deviation (RSD) of 2.4%. The accuracy of the self-heating HS-SPME was evaluated by analyzing a soil certified reference material (CRM) and nine soil samples with satisfactory recoveries (86-111%). Compared to the conventional external heating method, the proposed method reduces desorption time and power consumption from 80 s and 60 W to 20 s and 2.5 W, respectively. Moreover, the self-heating device enables the µPD-OES system to remove the high-temperature desorption chamber, making it more compact and suitable for field analytical chemistry. Interestingly, the Au@W SPME fiber can be also used for the long-term preservation of mercury with a sample loss rate <5% after 30 days of storage at room temperature.

Portable and Rapid Fluorescence Turn-On Detection of Total Pepsin in Saliva Based on Strong Electrostatic Interactions.

Salivary pepsin has been proposed as a promising diagnostic marker for gastroesophageal reflux disease (GERD). However, the activity of human pepsin is strongly influenced by pH, and the acidic condition (pH ∼ 2) is optimal, which is a contradiction for the pepsin detection kit based on its catalytic activity. Thus, its accurate quantification in saliva (neutral pH) by readily rapid tools with simplicity and low cost is still challenging. Herein, a convenient fluorescence assay has been developed for the rapid detection of pepsin at neutral pH based on its electrostatic interaction with SYBR Green (SG) rather than the bioactivity. At neutral pH, the positively charged SG fluorophore can be effectively adsorbed by the negatively charged pepsin due to the low isoelectric point (pI) and large molecular size of pepsin. Thus, the molecular rotation of SG is limited, and its fluorescence intensity is significantly increased. The strategy was further confirmed to have the same fluorescence response as that of normally active and inactivated pepsin. Due to the unique pI of pepsin, the fluorescence strategy is highly selective for pepsin compared to other proteins. On the basis of this strategy, a smartphone-based fluorescence capture device integrated with a programmed Python program was fabricated for both color recognition and the accurate detection of pepsin within 3 min. Under the optimal conditions, this turn-on sensor allowed for the on-site analysis of pepsin with a detection limit of 0.2 µg/mL. Moreover, this strategy was successfully used to assess salivary pepsin to aid in the noninvasive diagnosis of GERD.

Nozzle Electrode Point Discharge-Enhanced Oxidation and Portable Gas Phase Molecular Fluorescence Spectrometry for Sensitive Field Detection of Sulfide.

It is still a challenge to accurately determine dissolved sulfide due to its susceptibility to contamination and loss during transportation, storage, and analysis in the laboratory, thus highlighting the necessity for its sensitive field analysis. Herein, a robust nozzle electrode point discharge (NEPD) enhanced oxidation coupling with chemical vapor generation (CVG) is described for the highly efficient and flameless conversion of sulfide (S2-) to SO2. Subsequently, a portable and low-power consumption gas phase molecular fluorescence spectrometry (GP-MFS) was constructed for the highly selective and sensitive determination of the generated SO2 via detecting its molecular fluorescence excited by a zinc hollow cathode lamp. Under optimal conditions, a limit of detection (LOD) of 0.1 µM was obtained for dissolved sulfide with a relative standard deviation (RSD, n = 11) of 2.6%. The accuracy and practicability of the proposed method were validated by the analyses of two certified reference materials (CRMs) and several river and lake water samples with satisfactory recoveries of 99%-107%. This work confirms that NEPD enhanced oxidation is a low energy consumption yet highly efficient method for the flameless oxidation of hydrogen sulfide and thus is suitable for the easy field detection of dissolved sulfide in environmental water by CVG-GP-MFS.

Rapid Testing of Δ9-Tetrahydrocannabinol and Its Metabolite On-Site Using a Label-Free Ratiometric Fluorescence Assay on a Smartphone.

Excessive consumption of Δ9-tetrahydrocannabinol (THC) severely endangers human health and has raised public safety concerns. However, its quantification by readily rapid tools with simplicity and low cost is still challenging. Herein, we found that a G-rich THC aptamer (THC1.2) can tightly bind to thioflavin T (ThT) with strong fluorescence, which would be specifically quenched in the presence of THC. Based on that, a label-free ratiometric fluorescent sensor for the sensing of THC and its metabolite (THC-COOH) based on THC1.2/ThT as a color emitter and red CdTe quantum dots as reference fluorescence was constructed. Notably, a transition of the fluorescent color of the ratiometric probe from green to red can be instantly observed upon the increased concentration of THC and THC-COOH. Furthermore, a portable smartphone-based fluorescence device integrated with a self-programmed Python program was fabricated and used to accomplish on-site monitoring of THC and THC-COOH within 5 min. Under optimized conditions, this ratiometric fluorescent sensor allowed for an instant response toward THC and its metabolite with considerable limits of detection of 97 and 254 nM, respectively. The established sensor has been successfully applied to urine and saliva samples and exhibited satisfactory recoveries (88-116%). This ratiometric fluorescent sensor can be used for the simultaneous detection of THC and THC-COOH with the advantages of rapidness, low cost, ease of operation, and portability, providing a promising strategy for on-site detection and facilitating law enforcement regulation and roadside control of THC.

Nanozyme's catalytic activity at neutral pH: reaction substrates and application in sensing.

Nanozymes exhibit their great potential as alternatives to natural enzymes. In addition to catalytic activity, nanozymes also need to have biologically relevant catalytic reactions at physiological pH to fit in the definition of an enzyme and to achieve efficient analytical applications. Previous reviews in the nanozyme field mainly focused on the catalytic mechanisms, activity regulation, and types of catalytic reactions. In this paper, we discuss efforts made on the substrate-dependent catalytic activity of nanozymes at neutral pH. First, the discrepant catalytic activities for different substrates are compared, where the key differences are the characteristics of substrates and the adsorption of substrates by nanozymes at different pH. We then reviewed efforts to enhance reaction activity for model chromogenic substrates and strategies to engineer nanomaterials to accelerate reaction rates for other substrates at physiological pH. Finally, we also discussed methods to achieve efficient sensing applications at neutral pH using nanozymes. We believe that the nanozyme is catching up with enzymes rapidly in terms of reaction rates and reaction conditions. Designing nanozymes with specific catalysis for efficient sensing remains a challenge.

Determination of 93Mo in Radioactive Samples of Sulfuric Acid Media from Nuclear Facilities.

93Mo is an important radionuclide in view of radioactive waste repository because of its long half-life and high mobility in the environment. 93Mo decays by electron capture without any measurable gamma ray emission. The concentration of 93Mo in most of the radioactive waste is many orders of magnitude lower than the major activation product radionuclides, which makes the accurate determination of 93Mo a big challenge. A new analytical method for the determination of 93Mo in sulfuric acid media from nuclear power reactor was developed. 93Mo was separated from most of the radionuclides by cation exchange chromatography followed by the removal of sulfate by CaSO4 precipitation. A further purification of 93Mo, especially from anion species of 51Cr and 125Sb, was achieved by anion exchange chromatography and a short alumina column separation. The chemical yield of 93Mo in the entire separation procedure reached about 75%, and the decontamination factors for all potential interfering radionuclides were 1.5 × 106-1.6 × 108. The purified 93Mo was measured by liquid scintillation counting through counting its low-energy Auger electrons. A detection limit of 2 mBq/g for 93Mo in 50 g sample was achieved by this method, which enables the quantitative determination of 93Mo in most of the radioactive samples in the decommissioning waste and coolant water of nuclear power reactors. The developed method has been successfully applied to determine 93Mo in coolant water of nuclear power reactors, providing a robust analytical approach of 93Mo for the radiological characterization of radioactive wastes.

Sensitive and Environmentally Friendly Field Analysis of Waterborne Arsenic by Electrochemical Hydride Generation Microplasma Optical Emission Spectrometry.

To avoid polluting the environment, it is desirable to develop methods consuming as few chemicals as possible for field elemental analysis. In this work, a lithium-ion battery supplied, compact handheld optical emission spectrometer (OES) (0.3 kg, length 18 cm × width 5 cm × height 10 cm) was fabricated for the sensitive field analysis of waterborne arsenic by utilizing electrochemical hydride generation (ECHG) and miniaturized ballpoint discharge (µPD) as sample introduction means and excitation source, respectively. The high ECHG efficiency of arsenic was obtained using a superior cathode of Fe@PbO/Pb and the generated arsine was separated from an aqueous phase and further swept to the µPD microplasma for detection. It is worth noting that the Fe@PbO/Pb cathode not only retains advantages of large specific surface area, robust stability, and excellent reproducibility for the ECHG of arsenic but also accomplishes the preconcentration of As(III), thus improving the kinetics of the surface chemistry at the cathode, alleviating the corrosion of the electrode, and minimizing the release of Pb. A limit of detection of 1.0 µg L-1 was obtained with a relative standard deviation of 4.2% for 20 µg L-1 As(III). Owing to the advantages of ECHG and µPD-OES, the system retains a promising potential for the sensitive, cost-effective, and environmentally friendly field analysis of waterborne arsenic.

Learning from Headspace Sampling: a Versatile High-Throughput Reactor for Photochemical Vapor Generation.

Inspired by the headspace sampling (HS) device, a versatile high-throughput photochemical reactor with twenty vessels serving as both the photochemical vapor generator and the HS device was developed for the rapid and sensitive determination of mercury, nickel, and selenium by coupling photochemical vapor generation (PVG) to atomic fluorescence spectrometry (AFS) or point discharge optical emission spectrometry (µPD-OES). The photochemical reactor utilized a specially designed annular UV lamp around which the vessels containing sample solution were automatically rotated and irradiated to yield gaseous analyte species. Subsequently, the species escaped into the headspace of vessels prior to introduction to the atomic spectrometer. Compared with the conventional flow injection (FI) or continuous flow (CF) PVG, the developed PVG-HS method possesses several unique advantages including high throughput (260 pcs h-1), high sensitivity, and the elimination of matrix interference from transition metal ions and the memory effect associated with the quantification of mercury. Limits of detection (LODs) of 0.002, 0.007, and 0.01 µg L-1 were obtained for Hg (II), Ni (II), and Se (IV) by PVG-HS-AFS, respectively, and 0.02 and 0.2 µg L-1 were obtained for Hg (II) and Ni (II) by PVG-HS-µPD-OES, respectively. The practicality of the reactor was evaluated by the detection of Hg (II), Ni (II), and Se (IV) in five certified reference materials, including water (GBW08603, GBW08607, and GBW(E)080395), National Research Council Canada dogfish liver (DOLT-5), fish protein (DORM-4), and three river water samples with good recoveries (92-106%).

Headspace Solid-Phase Microextraction Following Chemical Vapor Generation for Ultrasensitive, Matrix Effect-Free Detection of Nitrite by Microplasma Optical Emission Spectrometry.

A new chemical vapor generation method coupled with headspace solid-phase microextraction miniaturized point discharge optical emission spectrometry (HS-SPME-µPD-OES) for the sensitive and matrix effect-free detection of nitrite in complex samples is described. In an acidic medium, the volatile cyclohexene was generated from cyclamate in the presence of nitrite, which was volatilized to the headspace of the container, efficiently separated, and preconcentrated by HS-SPME. Consequently, the SPME fiber was transferred to a laboratory-constructed thermal desorption chamber wherein the cyclohexene was thermally desorbed and swept into µPD-OES for its sensitive quantification via monitoring the carbon atomic emission line at 193.0 nm. As a result, the quantification of nitrite was accomplished through the determination of cyclohexene. The application of HS-SPME as a sampling technique not only simplifies the experimental setup of µPD-OES but it also preconcentrates and separates cyclohexene from N2 and sample matrices, thus eliminating the interference from water vapor and N2 and significantly improving the analytical performance on the determination of nitrite. Under the optimum experimental conditions, a limit of detection of 0.1 µg L-1 was obtained, which is much better than that obtained by conventional methods. The precision, expressed as relative standard deviation, was better than 3.0% at a concentration of 10 µg L-1. The proposed method provides several advantages of portability, simplicity, high sensitivity, and low energy consumption and eliminates expensive instruments and matrix interference, thus retaining a promising potential for the rapid, sensitive, and field analysis of nitrite in various samples.

Methanol-Enhanced Liquid Electrode Discharge Microplasma-Induced Vapor Generation of Hg, Cd, and Zn: The Possible Mechanism and Its Application.

Despite increased interest in microplasma-induced vapor generation (µPIVG) over the past several years, applications in real sample analyses remain limited due to their relatively low vapor generation efficiency and ambiguous mechanism. In this work, a novel method using methanol for significantly enhancing the liquid electrode discharge µPIVG efficiency was developed for the simultaneous and sensitive determination of Hg, Cd, and Zn by atomic fluorescence spectrometry (AFS). It is worth noting that the possible enhancement mechanism was investigated via the characterizations of volatile products by AFS, microplasma optical emission spectrometry, online gas chromatography, and gas chromatography-mass spectrometry, which involved the reductive species such as electrons, hydrogen radicals (·H), methyl radicals (·CH3), and other intermediates in the argon plasma adding methanol. Under the optimized conditions, the limits of detection of 0.007, 0.05, and 0.5 µg L-1 were obtained for Hg, Cd, and Zn, respectively, with relative standard deviations of 3.1, 3.7, and 5.2% for these elements, respectively. Vapor generation efficiencies of 90, 83, and 55% were achieved for Hg, Cd, and Zn, respectively, and improved 2.7-, 4.8-, and 7.9-fold, respectively, compared to those obtained in the absence of methanol. The accuracy and practicability of the proposed method were validated by the determination of Hg, Cd, and Zn in a certified reference material (CRM, Lobster hepatopancreas, TORT-3) and crayfish samples collected from three different provinces of China.

Three-Dimensional Printed Dual-Mode Chemical Vapor Generation Point Discharge Optical Emission Spectrometer for Field Speciation Analyses of Mercury and Inorganic Selenium.

Due to the large size and high energy consumption of instruments, field elemental speciation analysis is still challenging so far. In this work, a portable and compact system device (230 mm length × 38 mm width × 84 mm height) was fabricated by using three-dimensional (3D) printing technology for the field speciation analyses of mercury and inorganic selenium. The device comprises a cold vapor generator, photochemical vapor generator, and miniaturized point discharge optical emission spectrometer (µPD-OES). For mercury, inorganic mercury (IHg) was selectively reduced to Hg0 by cold vapor generation, whereas the reductions of both IHg and methylmercury (MeHg) were obtained by photochemical vapor generation (PVG) in the presence of formic acid. For selenium, Se(IV) and total inorganic selenium were converted to their volatile species by PVG in the presence and the absence of nano-TiO2, respectively. The generated volatile species were consequently detected by µPD-OES. Limits of detection of MeHg, IHg, Se(IV), and Se(VI) were 0.1, 0.1, 5.2, and 3.5 µg L-1, respectively. Precision expressed as the relative standard deviations (n = 11) were better than 4.5%. The accuracy and practicality of the proposed method were evaluated by the analyses of Certified Reference Materials (DORM-4, DOLT-5, and GBW(E)080395) and several environmental water samples with satisfactory recoveries (95-103%). This work confirms that 3D printing has great potential to fabricate a simple, miniaturized, easy-to-operate, and low gas and power consuming atomic spectrometer for field elemental speciation analysis.