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

Abstract

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.

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

“…In the previous work [22], the MCH-Pt/Ni trap system worked well for precise soil analysis. However, as shown in Figure 3, when introducing a 10 mg grain sample, the peak heights of Hg and Cd without CPF were obviously lower than those with the catalytic pyrolysis furnace, presumably due to matrix interference from the grain sample, especially the presence of organic substances.…”

“…The preconcentration of Hg and Cd is also essential to enhance sensitivity and eliminate interference for direct sampling. Our previous study [22] has demonstrated the co-trapping and releasing of Hg and Cd by the foamed platinum-nickel wafers. Considering the redesigned ETV system and grain sample matrix, the trapping, release, and working gas conditions need to be reinvestigated in this work.…”

“…Thus, this vaporizer may be ideal for rapid detection and field monitoring due to its low power and small size. Subsequently, the co-introduction of Hg and Cd via 100 W heating based on AFS detection was achieved for soil analysis; however, the AFS detector design complicates the apparatus and enlarges the instrument size, resulting in the impossibility of miniaturization and portability for the Hg-Cd analyzer [22].…”

“…However, the separate traps result in a low-level integration for the Hg-Cd analyzer. To further miniaturize the co-trapping device, a Pt/Ni composite trap was fabricated for simultaneous on-line trapping of Hg and Cd and specially designed for solid soil analysis; however, food matrices containing organic substances are more complicated than soil and interfere with the signals of Hg and Cd [22]. In fact, the original Pt/Ni composite trap without the integrated catalytic pyrolysis used in this study does not work well for the precise analysis of grain samples.…”

A Portable Microplasma Optical Emission Spectrometric Device with Online Digestion Function for Field and Sensitive Determination of Lead in Biological Samples

“…However, for field analysis, only sample introduction and detection are often focused on, and sample pretreatment in the field is ignored. As a result, most microplasma OES methods and devices are suitable for field analysis of environmental water samples instead of biological samples. − Although direct determination of heavy metals in biological samples can be achieved by electrothermal/electromagnetic heating vaporization, − the treated sample amount (0.15–20 mg) is very small, ,, leading to a higher detection limit. In addition, this method can only treat one sample at a time, greatly limiting the analytical throughput, and the high heating power makes it difficult to achieve long-term battery power, so it is still limited in field analysis.…”