A portable solid sampling visualization nano-sensor for soil Cd based on "three-phase transforming" technique.

Direct analysis of solid samples is always challenging for ionic sensors due to solidified elemental presence and matrix interference. In this work, a "three-phase transforming" technique was first established to make solid sampling elemental sensors and visual detection possible in the future. For Cd transforming from soil samples, a metal ceramic heater (MCH) electrothermal vaporizer (ETV) coupled with a dielectric barrier discharge quartz trap (DBD-QT) was first utilized to fulfill the solid sampling and preconcentration of Cd in soil; for on-site analysis, a colorimetric sensor based on the trithiocyanuric acid (TMT) functionalized gold nanoparticles (AuNPs) was chosen as a chromogenic analysis model. The portable and miniature ETV-DBD apparatus directly introduced Cd from soil and then captured Cd, consuming only <130 W and 4.5 kg weight; finally, only 200 µL water was injected as eluent to dissolve Cd for the following colorimetric detection. Herein, the Cd analyte underwent a "three-phase transforming" from solid (Cd compounds in soil), to aerosol (vaporization and transportation), to solid (Cd oxides trapped on quartz surface) and to liquid (Cd2+ in eluate). Under optimized conditions, the method limit of detection (LOD) reached 0.04 mg/kg Cd (50 mg sample), fulfilling fast monitoring of Cd contamination in soil, with <20 % relative standard deviations (RSDs). The analysis time was <10 min excluding sample digestion and acid application, as well as the interference of Pb2+ on the AuNPs sensor can be eliminated via the "three-phase transforming" process, proving an excellent anti-interference for solid analysis. This "three-phase transforming" processing technique coupled with colorimetric sensor holds a great potential for direct and on-site analysis in solid samples without complicated handling, providing a fantastic methodology for the application of ionic sensors and making solid sampling elemental sensor and visual detection possible.

Rapid and Portable Detection of Hg and Cd in Grain Samples Based on Novel Catalytic Pyrolysis Composite Trap Coupled with Miniature Atomic Absorption Spectrometry.

As toxic metals, Hg and Cd are a concern for food safety and human health; their rapid and portable analysis is still a challenge. A portable and rapid Hg-Cd analyzer constructed from a metal-ceramic heater (MCH)-based electrothermal vaporizer (ETV), an on-line catalytic pyrolysis furnace (CPF), a composite Pt/Ni trap, and a homemade miniature atomic absorption spectrometer (AAS) was proposed for grain analysis in this work. To enhance sensitivity, a new folded light path was designed for simultaneous Hg and Cd analysis using charge coupled device (CCD) in AAS. To eliminate the grain matrix interference, a catalytic pyrolysis furnace with aluminum oxide fillers was utilized to couple with a composite Pt/Ni trap. The method limits of detection (LODs) were 1.1 µg/kg and 0.3 µg/kg for Hg and Cd using a 20 mg grain sample, fulfilling the real sample analysis to monitor the grain contamination quickly; linearity R2 > 0.995 was reached only using standard solution calibration, indicating the sample was free of grain matrix interference. The favorable analytical accuracy and precision were validated by analyzing real and certified reference material (CRM) grains with recoveries of 97-103% and 96-111% for Hg and Cd, respectively. The total analysis time was less than 5 min without sample digestion or use of any chemicals, and the instrumental size and power consumption were <14 kg and 270 W, respectively. Compared with other rapid methods, this newly designed Hg-Cd analyzer is proven to be simple, portable, and robust and is, thus, suitable to quickly monitor Hg and Cd contamination in the field to protect grain and food safety.

Novel Platinum-Nickel Composite Trap for Simultaneous and Direct Determination of Mercury and Cadmium in Soil and Its Mechanism Study.

In this work, following a metal-ceramic heater (MCH) as an electrothermal vaporizer (ETV), a novel composite Pt/Ni trap based on platinizing the foamed nickel was first fabricated to trap Hg and Cd simultaneously. So, a solid sampling Hg-Cd analyzer was developed to simultaneously detect trace Hg and Cd in soil samples, mainly consisting of an MCH, a composite Pt/Ni trap, and an atomic fluorescence spectrometer (AFS). This small-size MCH-ETV system only consumes 100 W for the complete vaporization of Hg and Cd in soil matrices. The Pt/Ni trap fulfills the complete trapping of Hg and Cd following the solid sampling MCH-ETV system and then fast releases them by heating. It was proved that trapped and released Hg and Cd by the Pt/Ni trap are atomic species using X-ray photoelectron spectroscopy (XPS) and other approaches; specially, the effective cotrapping of Hg and Cd might be due to forming alloys of Hg + Pt and Cd + Ni on the Pt/Ni trap. Under the optimized conditions, the method detection limits (LODs) of Hg and Cd reached 0.4 µg/kg and 0.04 µg/kg for a 20 mg sample size, the relative standard deviations (RSDs) were within 12% and 8% for soil samples, respectively, and the recoveries ranged from 96% to 105%, indicating favorable analytical sensitivity, precision, and accuracy. The whole analysis time can be controlled within 5 min without the soil digestion process. The proposed Hg-Cd analyzer is thus suitable for rapid detection of Hg and Cd in soil samples with advantages such as simplicity, green, and safety. Further, the proposed solid sampling ETV-composite trap method has a promising application potential in the field and rapid detection for multielements.

Analytical Methodologies for Agrometallomics: A Critical Review.

Agrometallomics, as an independent interdiscipline, is first defined and described in this review. Metallic elements widely exist in agricultural plants, animals and edible fungi, seed, fertilizer, pesticide, feedstuff, as well as the agricultural environment and ecology, and even functional and pathogenic microorganisms. So, the agrometallome plays a vital role in molecular and organismic mechanisms like environmetallomics, metabolomics, proteomics, lipidomics, glycomics, immunomics, genomics, etc. To further reveal the inner and mutual mechanism of the agrometallome, comprehensive and systematic methodologies for the analysis of beneficial and toxic metals are indispensable to investigate elemental existence, concentration, distribution, speciation, and forms in agricultural lives and media. Based on agrometallomics, this review summarizes and discusses the advanced technical progress and future perspectives of metallic analytical approaches, which are categorized into ultrasensitive and high-throughput analysis, elemental speciation and state analysis, and spatial- and microanalysis. Furthermore, the progress of agrometallomic innovativeness greatly depends on the innovative development of modern metallic analysis approaches including, but not limited to, high sensitivity, elemental coverage, and anti-interference; high-resolution isotopic analysis; solid sampling and nondestructive analysis; metal chemical species and metal forms, associated molecular clusters, and macromolecular complexes analysis; and metal-related particles or metal within the microsize and even single cell or subcellular analysis.

On-line microplasma decomposition of gaseous phase interference for solid sampling mercury analysis in aquatic food samples.

In this work, dielectric barrier discharge (DBD) was first utilized to eliminate gaseous phase interference from complicated solid sample. So, a novel solid sampling Hg analyzer was first designed using a coaxial DBD reactor to replace catalytic pyrolysis furnace for sensitive mercury determination in aquatic food samples. The Hg analyzer mainly comprised an electrothermal vaporizer (ETV), a DBD reactor to decompose gaseous interfering substances including volatile organic compounds (VOCs), a gold-coil Hg trap to eliminate matrix interference and an atomic fluorescence spectrometer (AFS) as detector. These units were connected by a manifold integrating air and Ar/H2 (v/v = 9 : 1), fulfilling on-line decomposition of up to 12 mg dried aquatic food powder at ambient temperature. The proposed method detection limit (LOD) was 0.5 µg/kg and the relative standard deviations (RSDs) were within 5% for Hg standards as well as within 10% for real samples, indicating adequate analytical sensitivity and precision. In addition, the on-line DBD reactor consumes only 40 W, which is obviously lower than that (>300 W) of the commercial Hg analyzers; including the sample pre-treatment, the overall analysis could be completed within 5 min. This method is easier, greener and safer for Hg analysis in real samples obviating chemical reagents. The new DBD apparatus can facilitate the miniaturization and portability with low power consumption and instrumental size revealing its promising potential in direct Hg analysis instrumentation development.

A novel gas liquid separator for direct sampling analysis of ultratrace arsenic in blood sample by hydride generation in-situ dielectric barrier discharge atomic fluorescence spectrometry.

A novel direct sampling (DS-HG) system consisting of an enlarged gas liquid separator (GLS) coupled with a foam breaker was firstly utilized for the in-situ dielectric barrier discharge atomic fluorescence spectrometer (DBD-AFS). After direct dilution using 5% HCl (v:v), a prepared blood sample was introduced into the DS-HG with a UV digestion unit, of which arsenic hydrides directly generated from sample under 5% HCl (v:v) and 5 g/L KBH4 in 1.5 g/L KOH. Herein, the newly designed DS-HG is capable of effectively eliminating foam generation deriving from protein in blood sample. Then, arsenic hydrides were trapped by 11 kV discharging at 110 mL/min air, and released by 13 kV at 180 mL/min H2 orderly. Under the optimized conditions, the linearity ranged from 0.05 to 50 ng/mL with a regression coefficient (R2) = 0.996. The method detection limit (LOD) was 7 pg arsenic (0.14 ng/mL), and relative standard deviation (RSD) of 10 repeated measurements for a real blood sample was 4.2%, indicating a good precision. The spiked recoveries for real samples were in the range of 97%-102%. Furthermore, arsenic presence in real blood samples measured by the proposed method were consistent (P > 0.05) with the microwave digestion ICP-MS. The whole analytical time can be controlled within 8 min including sample dilution. As a matter of fact, it is a favorable progress for DBD technique to eliminate matrix interferences of real samples based on the gas phase enrichment (GPE) principle, with advantages such as excellent sensitivity, digestion-free, fast and simple operation. Thus, the recommended DS-HG-in-situ DBD-AFS are suitable to the fast analysis of ultratrace arsenic in blood samples to protect human's health.