Yong Tian

A disposable blood cyanide sensor

Deaths due to smoke inhalation in fires are often due to poisoning by HCN. Rapid administration of antidotes can result in complete resuscitation of the patient but judicious dosing requires the knowledge of the level of cyanide exposure. Rapid sensitive means for blood cyanide quantitation are needed. Hydroxocyanocobinamide (OH(CN)Cbi) reacts with cyanide rapidly; this is accompanied by a large spectral change. The disposable device consists of a pair of nested petri dish bottoms and a single top that fits the outer bottom dish. The top cover has a diametrically strung porous polypropylene membrane tube filled with aqueous OH(CN)Cbi. One end of the tube terminates in an amber (583nm) light emitting diode; the other end in a photodiode via an acrylic optical fiber. An aliquot of the blood sample is put in the inner dish, the assembly covered and acid is added through a port in the cover. Evolved HCN diffuses into the OH(CN)Cbi solution and the absorbance in the long path porous membrane tube cell is measured within 160 s. The LOD was 0.047, 1.0, 0.15, 5.0 and 2.2 μM, respectively, for water (1 mL), bovine blood (100 μL, 1 mL), and rabbit blood (20 μL, 50 μL). RSDs were<10% in all cases and the linear range extended from 0.5 to 200 μM. The method was validated against a microdiffusion approach and applied to the measurement of cyanide in rabbit and human blood. The disposable device permits field measurement of blood cyanide in <4 min.

Arsenic speciation with gradient hydride generation interfacing liquid chromatography and atomic absorption spectrometry

Arsenic speciation was performed based on liquid chromatographic separation followed by gradient hydride generation (GHG) and quartz atomizer atomic absorption spectrometric detection. The arsenic species, i.e., arsenate (As(V)), arsenite (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO), were separated on C30-5 columns, and the concept of gradient hydride generation facilitates high conversion efficiency of the arsenic species into corresponding hydrides. The use of 2% L-cysteine in the GHG process gives rise to further improvements on the hydride generation efficiency of 13% to 32% for the arsenic species. The hydrides were separated in a unique design of gas–liquid separator, which not only ensures a complete separation but minimizes the dispersion of hydrides when delivering into the atomizer, resulting in a maximum of 13-fold improvement on the sensitivity of As(V) compared to previous studies. A separation process was finished within 800 s by injecting 100 µL sample solution, achieving detection limits of 0.9, 1.4, 1.4, 1.6, 1.5 µg/L, respectively, for As(V), As(III), MMA, DMA and TMAO. Precisions of less than 3% and 6% RSD were obtained for the five arsenic species at 100 µg/L and 20 µg/L, respectively. Three arsenic species, i.e., As(V), DMA and TMAO, were identified in Hijiki samples by this procedure.

Arsenic preconcentration viasolid phase extraction and speciation by HPLC-gradient hydride generation atomic absorption spectrometry

A novel method for arsenic speciation is developed by interfacing solid phase preconcentration-liquid chromatography (LC) separation-gradient hydride generation (GHG)-quartz flame atomic absorption spectrometry (QFAAS). A MnO2 mini-column is used to preconcentrate the arsenic species of As(III), As(V), MMA and DMA, during which process, As(III) is converted to As(V)viaoxidation by MnO2, while other species remain unchanged. The recovery of As(V) (i.e., the total amount of arsenate and arsenite in the original sample), MMA and DMA from the MnO2 mini-column is facilitated by tetramethylammonium hydroxide (TMAH). After LC separation with C30 columns, arsenic species in the eluate are subject to gradient hydride generation with detection by QFAAS. On the other hand, cellulose fibre selectively adsorbs the chelating complex between As(III) and ammonium pyrrolidine dithiocarbamate (APDC). After elution with HNO3, As(III) in the original sample is quantified by graphite furnace atomic absorption spectrometry (GFAAS), and the amount of As(V) is obtained by subtraction. A sample volume of 2.0 mL derives enrichment factors of 14.0–19.2 for the arsenic species. By injecting 20 μL of eluate into the LC system (the eluate of As(III)-PDC complex is injected into the GFAAS), detection limits of 0.019, 0.33, 0.39, 0.62 μg L−1 are obtained for As(III), As(V), MMA and DMA respectively. RSDs of less than 4.2% are achieved at the level of 2 μg L−1 for As(V), MMA, DMA and 1 μg L−1 for As(III). The procedure is evaluated by speciating arsenic in snow water and Hijiki samples.

Cadmium preconcentration with bean-coat as a green adsorbent with detection by electrothermal atomic absorption spectrometry

A novel green/biodegradable adsorbent, mungbean-coat, has been investigated for the adsorption of ultra-trace amounts of cadmium. Carboxylic groups on the bean-coat effectively retain the cadmium ions via coordinative interactions. This well facilitates the adsorption of cadmium ions which can readily be recovered by acid elution. In practice, bean-coat is used to pack a mini-column for on-line adsorption and preconcentration of cadmium from environmental samples with detection by electrothermal atomic absorption spectrometry. By using a sample loading volume of 1.4 mL and an eluent volume of 70 μL, an enrichment factor of 19.8 along with a detection limit of 1.4 ng L−1 are achieved. A precision of 2.4% RSD at the level of 0.05 μg L−1 is derived. The present procedure has been applied for the determination of cadmium in certified reference materials (GBW08608 Trace Elements in Water and CRM 176 Trace Elements in a City Waste Incineration Ash) and a snow water sample. Fair agreements are reached between the certified values and the experimental results, in addition to a satisfactory spiking recovery for the snow water sample. In the present work, the use of green and biodegradable adsorbent as well as the elimination of use of organic solvent/eluent facilitates the development of a green analytical protocol.

Reactive extractive electrospray ionization tandem mass spectrometry for sensitive detection of tetrabromobisphenol A derivatives

Sensitive detection of tetrabromobisphenol A (TBBPA) and its derivatives, a group of emerging toxic contaminants, is highly necessitated in environmental investigation. Herein a novel analytical strategy based on reactive extractive electrospray ionization (EESI) tandem mass spectrometry for detection of tetrabromobisphenol A bis(2-hydroxyethyl ether) (TBBPA-BHEE), tetrabromobisphenol A bis(glycidyl ether) (TBBPA-BGE), tetrabromobisphenol A bis(allylether) (TBBPA-BAE), and tetrabromobisphenol S bis(allylether) (TBBPS-BAE) in industrial waste water samples was developed. Active silver cations (Ag(+)), generated by electrospraying a silver nitrate methanol solution (10 mg L(-1)), collides the neutral TBBPA derivatives molecules in the EESI source to form [M+Ag](+) complexes of the analytes under the ambient conditions. Upon collision-induced dissociation (CID), characteristic fragments of the [M+Ag](+) complexes were identified for confident and sensitive detection of the four TBBPA derivatives. Under the optimized experimental conditions, the instrumental limits of detection (LODs) of TBBPA-BHEE, TBBPA-BGE, TBBPA-BAE and TBBPS-BAE were 0.37, 0.050, 0.76, and 4.6 μg L(-1), respectively. The linear ranges extended to 1000 μg L(-1) (R(2)≥0.9919), and the relative standard deviations (RSDs), inter-day variation and intra-day variation were less than 7.8% (n=9), 10.0% (n=5), and 14.8% (n=1 per day for 5 days) for all derivatives. TBBPA derivative manufacturing industrial waste water, river water and tap water samples were fast analyzed with the proposed method. The contents of TBBPA derivatives were various in the collected samples, with the highest 19.9±0.3 μg L(-1) of TBBPA-BAE in the waste water samples.

Integrating preconcentration, tetrahydroborate immobilization, elution and chemical vapor generation onto a cellulose surface for the determination of cadmium with atomic fluorescence spectrometry

A cellulose fibre packed micro-column was used for sorption preconcentration of ultra-trace cadmium and successive coating of a thin layer of sodium tetrahydroborate solution. The retained cadmium was stripped with hydrochloric acid and in-situ vapor generation on the cellulose surface was initiated by reaction with the coated layer of reducing reagent. The vapor was detected by atomic fluorescence spectrometry (AFS). The integration of preconcentration, reducing reagent immobilization, elution and in-situ vapor generation onto the cellulose surface significantly simplifies the entire operation, where a single syringe pump suffices fluids delivery, providing sufficient stability and long-term reliability indicated by an intra-day RSD <5%. In addition, the detection limit and precision were significantly improved with respect to those obtained by a conventional elution approach. With a sampling volume of 1.0 mL, a quantitative retention of cadmium was obtained within a linear range of 0.01–1.0 μg L−1, along with an enrichment factor of 19.5 and a sampling frequency of 12 h−1. A precision of 1.9% at 0.2 μg L−1 was obtained and a detection limit of 3 ng L−1 was derived. The procedure was validated by analyzing certified reference materials of Riverine Water (SLRS-4), and Trace Elements in Water (GBW 08608), in addition to spiking recovery in a coastal sea water.

An electrochemical bisphenol A sensor based on one step electrochemical reduction of cuprous oxide wrapped graphene oxide nanoparticles modified electrode

Bisphenol A (BPA), as an important industrial material, has been widespread concerned in recent years as its endocrine disrupting effect. This study reported a novel bisphenol A sensor via a facile one step electrochemical reduction of graphene oxide (rGO) and cuprous oxide (Cu2O) nanocomposite modified glassy carbon electrodes. The characterization of the fabricated sensor was performed by scanning electron microscopy and X-ray spectroscopy. The prepared Cu2O-rGO electrode presented fast response, high sensitivity and low background current. The response of BPA on prepared electrode was 2.15 times higher than reduced graphene modified electrode. Under the optimized experimental parameters, the detection range of the modified electrode was from 1×10-7 to 8×10-5 M and the limit of detection was 5.3×10-8 M (S/N =3). The prepared Cu2O-rGO modified electrode has been successfully used for detecting BPA in environmental water samples.

High-temperature isopiestic studies on the ternary slag PbO-SiO2-B2O3 at 1273 K

An improved high-temperature isopiestic technique has been applied to the ternary slag PbO-SiO2-B2O3 and its binary subsystems PbO-SiO2 and PbO-B2O3 at 1273 K. The isopiestic measurements agree well with the literature data for the two binaries. Each entire isoactivity curve of PbO in the ternary slag was determined by only one experiment. The activities of SiO2 and B2O3 were then calculated analytically. The measured and calculated results for the ternary slag approximately fit a partial ideal solution model proposed previously.

Quantitative detection of nitric oxide in exhaled human breath by extractive electrospray ionization mass spectrometry

Exhaled nitric oxide (eNO) is a useful biomarker of various physiological conditions, including asthma and other pulmonary diseases. Herein a fast and sensitive analytical method has been developed for the quantitative detection of eNO based on extractive electrospray ionization mass spectrometry (EESI-MS). Exhaled NO molecules selectively reacted with 2-phenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) reagent, and eNO concentration was derived based on the EESI-MS response of 1-oxyl-2-phenyl-4, 4, 5, 5-tetramethylimidazoline (PTI) product. The method allowed quantification of eNO below ppb level (~0.02 ppbv) with a relative standard deviation (RSD) of 11.6%. In addition, eNO levels of 20 volunteers were monitored by EESI-MS over the time period of 10 hrs. Long-term eNO response to smoking a cigarette was recorded, and the observed time-dependent profile was discussed. This work extends the application of EESI-MS to small molecules (<30 Da) with low proton affinity and collision-induced dissociation efficiency, which are usually poorly visible by conventional ion trap mass spectrometers. Long-term quantitative profiling of eNO by EESI-MS opens new possibilities for the research of human metabolism and clinical diagnosis.

Silver ion post-column derivatization electrospray ionization mass spectrometry for determination of tetrabromobisphenol A derivatives in water samples

A rapid and sensitive method was developed for the identification and quantitation of tetrabromobisphenol A (TBBPA) derivatives in water samples. Six major TBBPA derivatives, including tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-BHEE), tetrabromobisphenol A bis(glycidyl) ether (TBBPA-BGE), tetrabromobisphenol A bis(allyl) ether (TBBPA-BAE), tetrabromobisphenol A mono(2-hydroxyethyl) ether (TBBPA-MHEE), tetrabromobisphenol A mono(glycidyl) ether (TBBPA-MGE) and tetrabromobisphenol A mono(allyl) ether (TBBPA-MAE), were selected as the target compounds. By applying the silver cation (Ag+) as the post-column derivatization reagent, the TBBPA derivatives formed complexes ([M + Ag]NO3) online, which could be effectively electrosprayed to generate ionic clusters ([M + Ag]+) for sensitive mass analysis. Under the optimized conditions, the 6 TBBPA derivatives were separated and detected within 10 min. The limits of detection (LODs) were between 0.16 and 1.96 μg L−1, and the linear ranges extended to 200 μg L−1 (R2 ≥ 0.9957). The relative standard deviations (RSDs) were less than 7.7% for 10 μg L−1 of the TBBPA derivatives (n = 7). The proposed method was successfully applied in analysis of environmental water samples. The spiked recoveries ranged from 81.3% to 114.9%, suggesting the accuracy and feasibility of the method.