Determination of different arsenic species in food‐grade spirulina powder by ion chromatography combined with inductively coupled plasma mass spectrometry

A “two‐step” pressurized microwave‐assisted extraction method coupled with ion chromatography with inductively coupled plasma mass spectrometry for the determination of different arsenic species in spirulina samples was developed. The extraction method used H₂O₂/H₂O (1:5, v/v) as solvent to extract all arsenic species except arsenite, which was extracted by using water as solvent. The extraction method had a satisfactory recovery (>96%) and took a short time (20.0 min). With our method, all arsenic species in spirulina samples were completely separated and determined with recoveries of 84–105% and relative standard deviations of 2–4%. Food‐grade spirulina powder samples from seven provinces (Inner Mongolia, Zhejiang, Fujian, Hainan, Yunnan, Jiangsu, and Guangxi) in China were analyzed using the optimized protocol. Arsenate was detected at the concentration range of 170–394 ng/g in all the spirulina samples. Dimethylarsinic acid was detected at the concentration range of 32–839 ng/g in spirulina from above‐six provinces except Guangxi. Monomethylarsonic acid (67 ± 3 ng/g) was detected only in spirulina from Yunnan province. Arsenite was detected at the concentration range of 28–147 ng/g in spirulina from above five provinces except Hainan and Guangxi. Five unknown organic arsenic species were found in spirulina from above six provinces except Guangxi.     

Electrical relaxation studies of olivine type nanocrystalline LiMPO4 (M=Ni,Mn and Co) materials

The olivine type LiMPO₄ (M=Ni, Mn and Co) materials were synthesized by solution combustion technique using glycine as fuel. The structural characterizations were explored to confirm the phase formation of materials. The scanning electron microscope was used to identify the morphology of olivine materials. The local structure and chemical bonding between MO₆ octahedral and (PO₄)^3- tetrahedral groups were probed by Raman spectroscopy. Grain and grain boundaries were contributed for ion relaxation and dc conduction in olivine materials. Two orders of enhancement in ionic conductivity was observed in these olivine materials than the reported value. Among all the explored olivine samples, LiMnPO₄ showed highest enhancement in conductivity due to weak Li–O bonding and largest unit cell volume.     

Silver-coated LiVPO4F composite with improved electrochemical performance as cathode material for lithium-ion batteries

Nano-structured LiVPO₄F/Ag composite cathode material has been successfully synthesized via a sol–gel route. The structural and physical properties, as well as the electrochemical performance of the material are compared with those of the pristine LiVPO₄F. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that Ag particles are uniformly dispersed on the surface of LiVPO₄F without destroying the crystal structure of the bulk material. An analysis of the electrochemical measurements show that the Ag-modified LiVPO₄F material exhibits high discharge capacity, good cycle performance (108.5 mAh g⁻¹ after 50th cycles at 0.1 C, 93% of initial discharge capacity) and excellent rate behavior (81.8 mAh g⁻¹ for initial discharge capacity at 5 C). The electrochemical impedance spectroscopy (EIS) results reveal that the adding of Ag decreases the charge-transfer resistance (R_ct) of LiVPO₄F cathode. This study demonstrates that Ag-coating is a promising way to improve the electrochemical performance of the pristine LiVPO₄F for lithium-ion batteries cathode material.     

Study of Microwave Irradiation Polymerization in the Presence of Different Carriers

ABSTRACT

The influence of the presence of an inorganic carrier in the polymerization systems was investigated in this paper. Ten polymerization systems that contained different inorganic carriers such as Al₂O₃, SiO₂ were studied. The ten polymerization systems are dibutyltin Maleate (DBTM) and allyl thiourea (AT), DBTM and stearic acid vinyl ester (SAVE), SAVE and maleic anhydride (MH), SAVE and acrylamide (AM), itaconic acid (IA) and AM, SAVE and IA, AM and MH, IA, sodium acrylate (AANa), AM. It was found that the activity of monomer can be changed in the presence of a carrier and furthermore, the different species of carrier influence the activity of same monomer differently in the polymerization.     

方便面中砷元素的形态分析

建立了硝酸提取,高效液相色谱一原子荧光联用技术测定方便面中不同砷形态的分析方法。样品经0．15mol／L盐酸溶液超声提取后离心过滤,上机测试。实验表明：砷的4种形态亚砷酸[As（Ⅲ）]、砷酸[As（V）]、一甲基胂酸（MMA）和二甲基胂酸（DMA）的线性范围为0-50μg／L,相关系数（r）均优于0．9990,检出限在2～8μg／L之间,砷各形态的测量重复性（以RSD表示）均小于5％,样品的加标回收率为78％-118％。同时用原子荧光光度计检测了样品中总砷,并将两种方法测定结果进行了对比,结果符合理论以及文献报道。该方法操作简单快速、结果准确可靠,适用于方便面中砷形态的分析测定。     

氢化物发生-原子荧光光谱法同时测定水中砷和锑

建立在硝酸介质中用氢化物发生-原子荧光光谱法同时测定水中砷和锑的方法。优化了仪器工作条件、酸度、硼氢化钾及还原剂浓度。砷、锑的线性范围为0～10．0μg／L;检出限分别为0．02,0．01μg／L;测定结果的相对标准偏差分别为1．77％～3．72％,2．95％～4．87％（n=6）;加标回收率分别为98％106％,96％105％。该法操作简便,灵敏度高,快速,便于推广,适用于水中砷和锑的同时测定。     

微波消解–原子荧光法同时测定PM2.5中砷、汞含量

采用微波消解–原子荧光法测定PM2.5中砷、汞含量。实验结果表明,当还原剂硼氢化钾的质量分数为2%、溶液介质酸度为4%(体积分数)盐酸时,同时测定砷、汞可获得最佳的荧光值。砷、汞测定的检出限分别为0.027,0.006μg/L,空白滤膜的加标回收率分别为95.3%~101.7%,96.0%~106.0%,样品的加标回收率分别为95.0%~103.5%,93.3%~110.0%。该法检出限低,准确度高,适用于环境空气PM2.5中砷、汞含量的测定。     

Effects of Inorganic Salts on Micellization and Solubilization in an Aqueous Solution of Poly(ethylene oxide)/Poly(propylene oxide)/Poly(ethylene oxide) Triblock Copolymer

The effects of inorganic salts on micellization and solubilization of prednisolone in aqueous solution of poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) triblock copolymer (Pluronic P85) were studied. The effect of inorganic salts on decrease in the cloud point and the critical micelle concentration (cmc) of Pluronic P85 was the order of Na₂HPO₄ > NaH₂PO₄ > NaCl > NaBr. Moreover, it was found that Pluronic P85 forms two kinds of micelles: monomolecular micelles and polymolecular micelles. The polymolecular micelle increased with increasing amount of added inorganic salts. Moreover, solubilization behavior is explained from the standpoint of salting out for prednisolone and association characteristics of Pluronic P85.     

Catalytic solid substrate-room temperature phosphorimetry for the determination of trace As(V) based on oxidising reaction between hydrogen peroxide and fullerenol using tween-80 as sensitizer

A new catalytic solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace arsenic(V) has been established. It is based on the fact that fullerenol (F-ol) emitted strong and stable room temperature phosphorescence (RTP) on nitric acid cellulose membrane (NCM) substrate. H₂O₂ could oxidise F-ol to cause the quenching of RTP. As(V) could catalyse H₂O₂ to oxidise F-ol and decrease the RTP signal of F-ol sharply. After adding tween-80 in the system, its ΔI _p enhanced 7.7 times compared with the without-tween-80 levels. Under the optimum conditions, the linear dynamic range of this method was 0.016?11.2 ag spot^?1 with a detection limit (LD) of 9.3 zg spot^?1 (corresponding concentration: 2.3 × 10^?17 g mL^?1). This sensitive, simple and selective method has been successfully applied to the determination of trace As(V) in human hair and tea samples. The reaction mechanism for SS-RTP is also discussed.