[Simultaneous determination of multi-organotin compounds in seawater by liquid-liquid extraction-high performance liquid chromatography-inductively coupled plasma mass spectrometry].

The hyphenated technique of high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was applied to the simultaneous determination of five organotin compounds (trimethyltin, dibutyltin, tributyltin, diphenyltin and triphenyltin) in seawater samples. Agilent TC-C18 column was used for the separation, the mobile phase of HPLC was CH3CN : H2O : CH3COOH = 65 : 23 : 12 (phi3), 0.05% TEA, and pH value was adjusted to 3.0 by diluent ammonia. The flow rate was 0.6 mL x min(-1). Five mixed organotin compounds in a mix standard solution from 100 to 0.5 microg x L(-1) were applied for the method assessment. The experimental results indicate that the correlation coefficient of calibration curves (R2) for each organotin compound was over 0.998 and the detection limits of the five organotin compounds were lower than 3 ng x L(-1). Different mixed organic solvents including dichloromethane or toluene were used for extraction of organotin and the extraction condition of organotin from seawater was optimized. The 100 mL seawater acidized by hydrochloric acid was extracted by 10 mL carbon dichloride (CH2 Cl2) with 2% tropolone for 10 min twice. Extracted organic solvents were mixed and blown to one drop by nitrogen with the rate of 1.7 mL x min(-1), then 1 mL acetonitrile was added to the drop for redissolving the organotin compounds. Finally, the mixed redissolution was filtered by 0.22 microm organic filter membrane before analysis. It was found that the only organotin compound in seawater was triphenyltin (TPHT) and the content was 53.2 ng x L(-1). The recoveries test from the standard addition for diphenyltin (DPHT), dibutyltin (DBT), tributyltin (TBT) and triphenyltin (TPHT) were over 80%. However, the recovery for trimethyltin (TMT) was relatively low and the value was 50%. The reason might be attributed to the decomposition or adsorption of those compounds during the extraction procedure. Further study on this subject is in progress.

Photo-enhanced gas sensing of SnS2 with nanoscale defects.

Recently a SnS2 based NO2 gas sensor with a 30 ppb detection limit was demonstrated but this required high operation temperatures. Concurrently, SnS2 grown by chemical vapor deposition is known to naturally contain nanoscale defects, which could be exploited. Here, we significantly enhance the performance of a NO2 gas sensor based on SnS2 with nanoscale defects by photon illumination, and a detection limit of 2.5 ppb is achieved at room temperature. Using a classical Langmuir model and density functional theory simulations, we show S vacancies work as additional adsorption sites with fast adsorption times, higher adsorption energies, and an order of magnitude higher resistance change compared with pristine SnS2. More interestingly, when electron-hole pairs are excited by photon illumination, the average adsorption time first increases and then decreases with NO2 concentration, while the average desorption time always decreases with NO2 concentration. Our results give a deep understanding of photo-enhanced gas sensing of SnS2 with nanoscale defects, and thus open an interesting window for the design of high performance gas sensing devices based on 2D materials.

[ICP-MS with octopole reaction system applied to isotopic analysis of iron in human fecal samples].

OBJECTIVE: The study was aimed to evaluate the application of the quadrupole inductively coupled plasma mass spectrometer (ICP-MS) with collision/reaction cell octopole reaction system (ORS) to determine the iron stable isotope ratio in human fecal samples. METHODS: In a field trial on human metabolism, 3.0 mg per subject of iron with 57Fe enriched was orally administrated, and feces were collected by fecal monitoring. The isotope ratio of 57Fe to 56Fe in the prepared fecal sample was detected with the ORS-ICP-MS. RESULTS: With the application of ORS-ICP-MS, interferences from the Ar plasma and the calcium-contained polyatomic ions could be eliminated. When the sample solution properly diluted, interferences from the matrix were too little to be noted. The relative stand deviation (RSD) of the long-term and short-term precision was < 0.3 %. From the changes of 57 Fe/56 Fe in the daily samples, a regularity of fecal iron outputs was presented, and the fractional iron absorption could be evaluated. CONCLUSION: The ratio of 57 Fe to 56 Fe in the fecal sample could be accurately determined by the quadrupole ICP-MS with ORS, based on which the dietary iron absorption could be evaluated and the metabolism of iron in the human body could also be traced.

[Determination of As and Se in animal and plant samples by the normal ICP-MS with and without octupole reaction system and the ICP-MS with ORS].

Scme certified reference materials (CRMs) were digested and the elemental concentrations were determined by ICP-MS instrument, and the results include not only the trace key elements such as As, Pb, Hg and Cd but also the major components such as Ca, Fe, K, Na etc. The digestion method, the recoveries, and the detection limits are discussed to piove the reliability of ICP-MS and EPA200.8 method for the determination of the elements in fcxxl and plant samples. The ICP-MS instrument with ORS (octupole reaction system) was applied to the determination of As, Se etc, and the results are compared with those from the normal ICP-MS without ORS. The removal of ArCl and ArAr interference is discussed, and the advantage of ORS is proved by measuring the As and Se in some CRMs.

Transfer of metals from soil to vegetables in an area near a smelter in Nanning, China.

A field survey was conducted to investigate the metal contamination in soils and vegetables, and to evaluate the possible health risks to local population through foodchain transfer near a smelter in Nanning, southern China. Contamination levels in soils and vegetables with cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) were measured, and transfer factors (TF) from soils to vegetable plants and its health risk (risk index, RI) were calculated accordingly. Results showed that both soils and vegetables from villages 1 and 2 (V1 and V2, 1500 m and 500 m from the smelter) were heavily contaminated, compared to a village 50 km from the smelter. Geometric mean of Cd and Pb concentrations in vegetables for V1 and V2, respectively, were 0.15 and 0.24 mg Cd kg(-1) and 0.45 and 0.38 mg Pb kg(-1) (on fresh weight basis). Oral intake of Cd and Pb through vegetables poses high health risk to local residents. Risk indices for V1 and V2, respectively, were 3.87 and 7.42 for Cd, and 1.44 and 13.5 for Pb. The complexity of metal contamination and their health risks are also discussed.