Xiandeng Hou

Photo-induced chemical vapor generation with formic acid for ultrasensitive atomic fluorescence spectrometric determination of mercury: potential application to mercury speciation in water

A new photochemical reaction for mercury chemical/cold vapor generation (CVG) coupled to atomic fluorescence spectrometry (AFS) is described for the speciation analysis of inorganic mercury ion (Hg2+) and organic methylmercury (MeHg) in aqueous solution. The new CVG simply uses one reagent, formic acid only, to react with Hg2+ or MeHg in aqueous solution, under room natural light (Vis) or ultraviolet irradiation (UV), for the generation of cold mercury vapor, which is subsequently detected by AFS. In the presence of the UV, both Hg2+ and MeHg can be converted to Hg0 for the determination of total mercury; and only Hg2+ can be reduced to Hg0 with the Vis, thus determining Hg2+ only. Then, the concentration of MeHg can be calculated by subtracting the Hg2+ concentration from the total mercury concentration. The optimal conditions for the best CVG efficiency are discussed, together with the interference from transition metals. There exists no significant interference from as high as 100 mg L−1 Co2+ or Ni2+, and 50 mg L−1 Cu2+ for the determination of as low as 5 μg L−1 Hg2+. The new CVG minimizes the contamination sources and avoids off-line pre-oxidation of MeHg. A simple Hg2+ standard series can be used for the calibration of both Hg2+ and MeHg, eliminating the use of more toxic and more expensive MeHg standard series. The linear dynamic ranges of the calibration curves are up to 25 μg L−1 with the UV and 300 μg L−1 with the Vis. The limit of detection is 0.003 or 0.2 μg L−1 for total mercury with the UV or Hg2+ with the Vis, respectively. The accuracy of this method was validated by determination of mercury in one certified reference water sample. The new CVG is a simple, fast, green, highly selective, and ultrasensitive yet inexpensive method for the speciation analysis of Hg2+ and MeHg. It is expected to have similar applications in other analytical atomic spectrometric techniques.

Applications of chemical vapor generation in non-tetrahydroborate media to analytical atomic spectrometry

Chemical vapor generation (CVG) using tetrahydroborate(III) remains the most popular and successful derivatization procedure enabling gaseous sample introduction into analytical atomic spectrometers that are routinely used for the determination of trace and ultratrace amounts of hydride-forming elements as well as Cd and Hg. The number of elements amenable to tetrahydroborate(III)-derivatization has recently been extensively enlarged. Despite its many obvious advantages, drawbacks remain, such as significant interferences from transition metals. Consequently, many alternative approaches have been developed to overcome these shortcomings and to further expand the suite of elements amenable to CVG for sample introduction. This article reviews these non-tetrahydroborate-based approaches, including photochemical vapor generation (photo-CVG), borane complexes CVG, alkylation based on Grignard reactions and derivatization with NaBEt4, cold vapor generation with SnCl2, halide generation, electrochemical hydride generation, oxide generation, and generation of volatile chelates. Special attention is given to two newly developed CVG approaches: photo-CVG and reduction in the presence of cyanoborohydrides.

Highly Sensitive Immunoassay Based on Immunogold−Silver Amplification and Inductively Coupled Plasma Mass Spectrometric Detection

In this work, we demonstrated a highly sensitive inductively coupled plasma mass spectrometric (ICPMS) method for the determination of human carcinoembryonic antigen (CEA), which combined the inherent high sensitivity of elemental mass spectrometric measurement with the signal amplification of catalytic silver deposition on immunogold tags. The silver amplification procedure was easy to handle and required cheap reagents, and the sensitivity was greatly enhanced to 60-fold after a 15 min silver amplification procedure. The experimental conditions, including detection of gold and silver by ICPMS, immunoassay parameters, silver amplification parameters, analytical performance, and clinical serum samples analysis, were investigated. The ICPMS Ag signal intensity depends linearly on the logarithm of the concentration of human CEA over the range of 0.07-1000 ng mL(-1) with a limit of detection (LOD, 3σ) of 0.03 ng mL(-1) (i.e., 0.15 pM). The LOD of the proposed method is around 2 orders of magnitude lower than that by the widely used enzyme-linked immunosorbent assay (ELISA) and 1 order of magnitude lower than that by clinical routine chemiluminescence immunoassay (CLIA) or time-resolved fluoroimmunoassay (TRFIA) and conventional ICPMS immunoassay. The present strategy was applied to the determination of human CEA in clinical human serum samples, and the results were in good agreement with those obtained by chemiluminescence immunoassay.

Electrochemically Generated versus Photoexcited Luminescence from Semiconductor Nanomaterials: Bridging the Valley between Two Worlds

from Semiconductor Nanomaterials: Bridging the Valley between Two Worlds Peng Wu,†,‡ Xiandeng Hou,‡ Jing-Juan Xu,*,† and Hong-Yuan Chen*,†,§ †State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China ‡Analytical & Testing Center, Sichuan University, Chengdu 610064, China Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Shandong Normal University, Jinan 250014, P.R. China

Determination of cadmium in rice and water by tungsten coil electrothermal vaporization-atomic fluorescence spectrometry and tungsten coil electrothermal atomic absorption spectrometry after cloud point extraction.

In this work, the microsampling nature of tungsten coil electrothermal vaporization Ar/H(2) flame atomic fluorescence spectrometry (W-coil ETV-AFS) as well as tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) was used with cloud point extraction (CPE) for the ultrasensitive determination of cadmium in rice and water samples. When the temperature of the extraction system is higher than the cloud point temperature of the selected surfactant Triton X-114, the complex of cadmium with dithizone can be quantitatively extracted into the surfactant-rich phase and subsequently separated from the bulk aqueous phase by centrifugation. The main factors affecting the CPE, such as concentration of Triton X-114 and dithizone, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimal conditions, the limits of detection for cadmium by W-coil ETV-AFS and W-coil ET-AAS were 0.01 and 0.03 microg L(-1), with sensitivity enhancement factors of 152 and 93, respectively. The proposed methods were applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with certified values.

Determination of Cadmium in Biological Samples

Abstract Even though normal exposure levels to Cd may be small, the human body is inefficient at excreting the heavy metal, so it slowly accumulates over the period of a lifetime. Eventually, the Cd level in the body may become toxic and give rise to harmful effects. Cadmium exposure could therefore be linked to diseases associated with aging such as osteoporosis, prostate cancer, and pancreatic cancer. These potential links have driven the development of a myriad of analytical techniques for the determination of Cd in biological samples. Natural biological Cd concentrations are typically low, so preconcentration steps and sensitive instruments are frequently a necessity. In addition, the complex matrices of biological specimens such as blood, urine, serum, and tissue often require a form of matrix modification or separation. This review provides an overview of these methods with 200 references from the literature published between 1995 and 2005. The analytical methods for the determination of Cd in biological samples include: spectrophotometry, atomic emission spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma mass spectrometry, and electrochemistry. In addition, Cd speciation techniques, using high‐performance liquid chromatography and capillary electrophoresis, are briefly discussed. Amanda C. Davis and Peng Wu contributed equally to this work.

Recent Advances in Portable X‐Ray Fluorescence Spectrometry

Abstract X‐ray fluorescence (XRF) spectrometry is a nondestructive, rapid, simultaneous multi‐element analytical methodology for solid or liquid samples. Its applications are broad and XRF spectra cover most elements, with a dynamic range from 100% down to the µg/g level. X-ray fluorescence is a well‐established laboratory‐based method, but it is also one of the few atomic spectrometric techniques that can be used for field portable instrumentation. In this manuscript, the recent advances in portable XRF spectrometry are reviewed with 80 references. The principles and instrumentation are briefly discussed, and many applications of the technique are described, including the analysis of soils, sediments, waters, liquid wastes, air, dust, archaeological artifacts, works of art, paint, metals, alloys, minerals, and forensic samples. Portable XRF is especially suitable for fast screening applications when the specific analytes of interest are unknown. The technique does not have accuracy and limit of detection (LOD) values comparable to those of conventional laboratory‐based atomic spectrometric techniques, such as inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, or electrothermal atomization atomic absorption spectrometry, but it finds its niche in its portability.

Temperature and nano-TiO2 controlled photochemical vapor generation for inorganic selenium speciation analysis by AFS or ICP-MS without chromatographic separation

A simple yet ultrasensitive UV photochemical vapor generation (photo-CVG) is proposed for the speciation analysis of Se(IV) and Se(VI). The new photo-CVG, which is based on Se(IV) or Se(VI) reacting with an organic acid under different reaction conditions, can be coupled to AFS or ICP-MS for the speciation analysis of Se(IV) and Se(VI) in real samples such as table salt and water samples without chromatographic separation. At low temperature, only Se(IV) can be photochemically converted to selenium volatile species, and this is used for its selective determination; however, by using boiling water bath together with nano-TiO2 as a catalyst, both Se(IV) and Se(VI) can be photochemically converted to selenium volatile species, thus determining the total of Se(IV) and Se(VI). Therefore, Se(VI) concentration can be calculated from the difference between the total and Se(IV) concentration. Optimal reaction conditions and instrumental parameters are investigated; and the interferences from transition metals and other ions, as well as the photo-CVG mechanism, are discussed. The limits of detection range from 0.02 to 0.1 ng mL−1, depending on the kind of organic acid and the detector. The accuracy of the method is validated by determining Se(IV) in certified reference water sample. Real samples including commercial table salt, waste water and mineral water were successfully analyzed. This is a simple, relatively green, highly selective and sensitive, yet inexpensive method for the speciation analysis of Se(IV) and Se(VI).

Recent Advance of Hydride Generation–Analytical Atomic Spectrometry: Part I—Technique Development

Abstract Hydride generation is the most popular and widely used chemical vapor generation technique and is interesting to analytical chemists as an effective sample introduction method, especially for elemental determination and speciation analysis by analytical atomic spectrometry. The present review provides a literature survey on the hydride generation technique coupled to analytical atomic spectrometry during the past several years, covering the literature on both tetrahydroborate-based hydride generation and non-tetrahydroborate-based hydride generation techniques. Development of other related methods coupled to hydride generation for better analytical performance of analytical atomic spectrometry is included as well.

An ethanol sensor based on cataluminescence on ZnO nanoparticles

A novel gas sensor for the determination of ethanol was proposed in the present work, which was based on the generated cataluminescence emission from catalytic oxidation of ethanol on the surface of ZnO nanoparticles. The cataluminescence characteristics and the effect of different parameters on the signal intensity, such as morphology of synthesized ZnO, temperature and flow rate, were discussed in detail. Under the optimized experimental conditions, the calibration curve of cataluminescence intensity versus ethanol vapor concentration was linear in the range 1.0-100ppm, and with a detection limit of 0.7ppm (S/N=3). Compared with the traditional electrical conductivity-based ZnO gas sensor for the determination of ethanol, the proposed ethanol sensor showed the advantages of high sensitivity, high selectivity and low working temperature.