食品中脱氢乙酸测定的快速前处理方法

本文建立了一种适用于食品中脱氢乙酸等常见防腐剂的简便快速的前处理方法。样品采用乙酸乙酯为提取液,通过加速的溶剂萃取仪(ASE)萃取,萃取液通过凝胶渗透色谱仪(GPC)后,进GC-FID检测。脱氢乙酸在1.0～200.0mg/kg范围内呈现良好的线性关系,检出限为1.0mg/kg(S/N≥3),添加平均回收率为89%～102%,RSD1O%。该方法同时结合了筛选和确证两个过程,选择性好,回收率高,可靠性强,简单快捷,符合分析要求。     

UPLC-MS/MS法同时测定外卖食品接触材料中7种抗氧化剂的迁移量

采用UPLC-MS/MS法，建立同时测定外卖食品接触材料中7种抗氧化剂迁移量的定量分析方法。结果表明：7种目标化合物在0.05～1.0 mg/L及0.5～10 mg/L范围内具有较好的线性关系，相关系数R2≥0.99；方法检出限为0.02～0.2mg/kg，定量限为0.05～0.5 mg/kg；方法的回收率为81.4%～116.1%，相对标准偏差为1.1%～9.8%。该方法前处理简单，灵敏度高，适用于外卖食品接触材料中抗氧化剂迁移量的定量分析。     

气相色谱-质谱法测定土壤中苯胺的方法确认研究

研究了气相色谱-质谱法测定土壤中苯胺的非标方法确认过程。通过三家实验室间的比对得出:苯胺的检出限为0.02mg/kg～0.03mg/kg,测定下限为0.08mg/kg～0.12mg/kg,三家实验室分别对加标浓度为0.25mg/kg、0.50mg/kg和1.0mg/kg的样品进行测定,实验室内相对标准偏差为2.5%～9.2%、1.0%～6.0%、2.0%～7.2%,重复性限为0.021mg/kg、0.038mg/kg、0.083mg/kg,再现性限为0.089mg/kg、0.091mg/kg、0.174mg/kg,加标回收率最终值为(66.6±10.0)%、(64.2±8.6)%、(63.0±7.2)%,各项指标均达到预期要求,满足土壤中苯胺的测定。     

凝胶渗透色谱-高效液相色谱法测定食品中酚类抗氧化剂

本文采用凝胶渗透色谱对食品进行脱油脂前处理,高效液相色谱仪(DAD检测器)对酚类抗氧化剂进行定性定量分析。该方法在实际样品检测中加标回收率在86.3%-105.3%间,相对标准偏差小于9.6%,最低检测限为1μg/mL。与国家标准方法相比,该方法可同时检测4种酚类抗氧化剂,具有较高的准确性与灵敏度,适用于食品中PG、TBHQ、BHA与BHT的检测。     

气相色谱法测定果蔬汁饮料中6种防腐剂

采用气相色谱仪(Agilent 6890N)配备火焰离子化检测器(FID)测定果蔬汁饮料中山梨酸、苯甲酸、脱氢乙酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯和对羟基苯甲酸丙酯6种防腐剂的含量.试样在酸性条件下,经乙醚一次提取后,采用稀释倍数法,移取少量提取液,浓缩近干,最后用丙酮定容.在10,30,50,70,100mg/kg5个加标水平下,6种防腐剂的回收率为87.8%～105.5%,相对标准偏差为0.8%～3.1%,检出限为0.4～1.0mg/kg.实验表明该方法样品前处理简便、快速,分析结果可靠.     

QuEChERS-高效液相色谱-串联质谱法测定干红菇中8种农药残留

本文旨在建立一种基于QuEChERS前处理与高效液相色谱-串联质谱(high performance liquid chromatog-raphy-tandem mass spectrometry,HPLC-MS/MS)联用测定干红菇中8种农药(多菌灵、甲基硫菌灵、精甲霜灵、戊唑醇、苯醚甲环唑、肟菌酯、吡虫啉、克百威)残留量的分析方法。样品采用乙腈/水经QuEChERS方法提取净化,在HPLCMS/MS系统的多反应监测模式(multiple reaction monitoring,MRM)下进行8种农药的定量和定性分析。8种农药在1.0～250.0μg/L的范围内呈现良好线性关系,相关系数r2均大于0.998;方法的检出限和定量限分别为0.4～2.0μg/kg和1.3～6.5μg/kg;在3个加标水平下(0.005、0.10、0.50 mg/kg),加标回收率为81.2%～95.3%,相对标准偏差(relative standard deviation,RSD)为1.08%～6.13%。本方法的重复性和回收率满足实验要求,适用干红菇中部分农药残留的快速分析检测。     

QuEChERS/高效液相色谱测定食品中15种多环芳烃

建立了检测食品中15种多环芳烃(PAHs)的QuEChERS/高效液相色谱分析方法。样品经正己烷超声萃取,浓缩后用乙腈溶解,采用含100 mg PSA和100 mg C18填料粉进行净化。净化后,采用高效液相色谱-荧光检测器进行分析测定。在最优化色谱条件下,15种PAHs在1.0~100μg/L范围内,线性关系良好,方法检出限(S/N=3)为0.1~0.9μg/kg,方法的定量限(S/N=10)为0.3~3.0μg/kg。回收率在65~120%,相对标准偏差(RSD)小于15%。该方法具有数据可靠、简便快速,灵敏度高,适合于食品中多环芳烃的测定。     

加速溶剂萃取气相色谱-质谱法检测土壤中双酚A

建立加速溶剂萃取后利用气相色谱-质谱法测定土壤中双酚A的检测方法。样品前处理采用加速溶剂萃取,经硅胶柱净化,以HP-5MS色谱柱,采用气相色谱-质谱联用全扫描和选择离子扫描进行分析。结果表明:双酚A在0.1~10.0 mg/L的质量浓度范围内,线性良好,相关系数为0.999 3;方法检出限为0.01 mg/kg(S/N=3)。在0.1,1.0,10 mg/kg这3个加标水平下,样品的平均回收率为82.5%~101.7%,相对标准偏差(RSD)≤3.3%。该方法简便快速,灵敏度及准确度高,可用于土壤中双酚A的分析测定。     

文具产品中6种邻苯二甲酸酯的测试

提出气相色谱-质谱联用仪同时测定文具中6种邻苯二甲酸酯类增塑剂的方法,以正己烷为溶剂,采用索氏提取法提取文具中6种邻苯二甲酸酯类增塑剂,采用外标法进行定量。该方法平均回收率为87.6%¹03.1%,相对标准偏差为0.45%103.1%,相对标准偏差为0.45%⁴.17%,检出限分别为0.5mg/kg(邻苯二甲酸二丁酯DBP),0.75mg/kg(邻苯二甲酸丁苄酯BBP),0.75 mg/kg[邻苯二甲酸二(2-乙基)己酯DEHP],1.0 mg/kg(邻苯二甲酸二正辛酯DNOP),5.0 mg/kg(邻苯二甲酸二异壬酯DINP),5.0mg/kg(邻苯二甲酸二异癸酯DIDP)。     

火焰原子吸收法测定海沙中锌、铜、铅

本文比较了三种不同酸消化处理海沙样品及不同酸度溶解残渣后用火焰原子吸收测定海沙中锌、铜、铅的方法,实验结果表明:前处理选择硝酸-高氯酸-氢氟酸法消化样品,用5%盐酸溶解残渣后测定,结果满意,方法检出限Zn0.52mg/kg,Cu0.075mg/kg,Pb1.9mg/kg,相对标准偏差(RSD)为1.3%～1.9%,加标回收率为99%～105%,该方法适用于海沙中重金属的测定。     

Mechanochemical fabrication of C (matrix) + Cu + Si + W + Mo nanocomposites

Using magnesiothermic reduction of WO₃, MoO₃, SiO₂, and CuO through mechanochemical activation, we prepared high-purity (∼99.3%) nanopowders with a particle size from 9 to 350 nm for the fabrication of functional materials and nanocomposite systems for anode electrodes of lithium ion (polymeric) batteries.     

新西兰JAG CREATIVE:品牌、营销与推广

为这个真实世界进行品牌与平面设计创作就是新西兰Jag Creative品牌设计公司的热情。作为一个岛国,新西兰的企业在创新与创造性方面有着令人惊叹的杰出表现。     

高密度发光材料γ-Bi2WO6:Pr3+的发光性质研究

研究了用固相法制备的高密度发光材料γ-Bi2WO6Pr3+的结构、光致发光光谱、激发谱和γ-Bi2WO6的漫反射谱.由实验测得它的晶格参数为a=5.45A,b=16.42A,c=5.43A,密度Dx=9.53g/cm3.它的光致发光光谱主发射峰位于600、608、611、629nm,分别来自于pr3+的1D2→3H4、3P0→3H5、3P0→3H6、3P0→3F2跃迁的发射.其激发谱由位于约225～430nm范围内、最大值约在372nm的主激发带和450nm的激发峰组成;主激发带来自于基质,可能是基质的带间吸收、W-O间电荷迁移吸收和缺陷能级的吸收;450nm的激发峰来自于pr3+的3H4→3P2跃迁吸收.BWOPr3+的最佳掺杂浓度为0.8mol%左右.     

Electrical characterization of Si+ and Si+/P+ implanted N+P+In0.53Ga0.47As junctions

In this communication, we present I–V and admittance spectroscopy measurements of shallow n⁺p junctions into p-InGaAs made by Si⁺ implantation, including a complete study of the conduction mechanisms as a function of temperature. The effect of P⁺ co-implantation is also analysed. The I–V characteristics of both junctions show that recombination in the space-charge zone is the dominant transport mechanism in forward bias, with ideality factors around 1.5 at 300 K that increase with decreasing temperature of measurement. Activation energies of the reverse saturation current are obtained at room temperature, being 0.5 eV and 0.4 eV for Si⁺ and Si⁺P⁺ implanted diodes, respectively, indicating that recombination currents occur through a near midgap center. Reverse current–voltage measurements show a higher conduction in the P⁺ co-implanted junction due to a higher concentration of traps. In both types of junctions, the reverse characteristics can be fitted to a thermally-activated trap-assisted tunneling mechanism at low bias, involving traps at 0.41 eV and 0.44 eV for Si⁺ and P⁺ co-implanted junctions, respectively, whereas different trap-assisted tunneling processes dominate at medium and high bias. The small signal analysis show a clear difference between the two types of junctions. The use of Kramers–Kronig transforms on the admittance spectroscopy data reveals the presence of a defect level at 0.35 eV in both types of junctions, probably assigned to Zn, the native acceptor present in the p-InGaAs. Another trap level at 0.30 eV is detected at the P⁺ co-implanted junctions, not appearing in the Si doped junctions, which could probably be due to damage produced by the co-implantation.     

(Sr2+,Bi3+,Si4+,Ta5+)掺杂的TiO2压敏陶瓷中Ta5+的研究

研究Ta2 O5对 (Sr,Bi,Si,Ta)掺杂的TiO2 基压敏陶瓷压敏特性及电容特性的影响 ,发现按配方TiO2 0 .3%(SrCO3 Bi2 O3 SiO2 ) 0 .1 %Ta2 O5配制的样品具有最低压敏电压 (E1 0mA =1 .2V·mm- 1 )、最大相对介电常数 (εra=2 .0 0 2× 1 0 5)及较小非线性系数 (α =2 .6 )。考虑到材料的低压敏电压和大介电常数的要求 ,Ta2 O5最佳掺杂量在 0 .0 85mol%与 0 .1mol%之间。     

（Sr^2＋，Bia^3＋，Si^4＋，Ta^5＋）掺杂的TiO2压敏陶瓷中Ta^5＋的研究

研究Ta2O5对(Sr,Bi,Si,Ta)掺杂的TiO2基压敏陶瓷压敏特性及电容特性的影响,发现按配方TiO2+0.3%(SrCO3+Bi2O3+SiO2)+0.1%Ta2O5配制的样品具有最低压敏电压(E10mA=1.2V·mm-1)、最大相对介电常数(εra=2.002×105)及较小非线性系数(a=2.6).考虑到材料的低压敏电压和大介电常数的要求,Ta2 O5最佳掺杂量在0.085mol%与0.1mol%之间.     

Measurement of solubility and density of water + lithium bromide + lithium chloride and water + lithium bromide + sodium formate systems

Solubility of aqueous solutions containing lithium bromide + lithium chloride and lithium bromide + sodium formate were measured (LiBr/NaHCO₂ = 2 and LiBr/LiCl = 2 by mass ratio) at different temperatures. Visual polythermal method was used in the temperature range of (283.15–340.15) K and mass fraction range of (0.4–0.8). Also density of mentioned systems was reported in the temperature range of (288.15–333.15) K. Each set of experimental measurements were correlated using least-square regression as a function of temperature. Our results indicate that solubility of LiBr + LiCl is higher than LiBr and its density is lower than density of aqueous solution of LiBr.     

Phase Composition of the Products of Fe Oxidation in Fe + C + NaCl + H2O + O2 Exothermic Mixtures

Using thermodynamic analysis of the Fe–C–NaCl–H₂O–O₂ system and experimental studies (x-ray diffraction and Mössbauer spectroscopy) of exothermic mixtures containing Fe metal, activated carbon, water, and NaCl, we identified the state of Fe and determined the phase composition of the reaction products at different stages of oxidation with atmospheric oxygen. The calculation and experimental results are in reasonable agreement. Under the conditions of restricted access for air, the main oxidation product is magnetite, Fe₃O₄. Free access for air leads to the formation of hydrous ferric oxide, Fe₂O₃ · nH₂O. The most stable phase under the conditions of interest is goethite, Fe₂O₃ · H₂O (-FeOOH). Storage of incompletely oxidized samples away from air for 7–14 days leads to partial reduction of iron(III) oxide phases to Fe₃O₄ and -Fe.     

Solubilities, Vapor Pressures, and Heat Capacities of the Water + Lithium Bromide + Lithium Nitrate + Lithium Iodide + Lithium Chloride System

The optimum mole ratio of lithium salts in the H₂O + LiBr + LiNO₃ + LiI + LiCl system was experimentally determined to be LiBr : LiNO₃ : LiI : LiCl = 5 : 1 : 1 : 2. The solubilities were measured at temperatures from 252.02 to 336.75 K. Regression equations on the solubility data were obtained with a least-squares method. Average absolute deviations of the calculated values from the experimental data were 0.15% at temperatures <285.18 K and 0.05% at temperatures 285.18 K. The vapor pressures were measured at concentrations ranging from 50.0 to 70.0 mass% and at temperatures from 330.13 to 434.88 K. The experimental data were correlated with an Antoine-type equation, and the average absolute deviation of the calculated values from the experimental data was 2.25%. The heat capacities were measured at concentrations from 50.0 to 65.0 mass% and temperatures from 298.15 to 328.15 K. The average absolute deviation of the values calculated by the regression equation from the experimental data was 0.24%.     

Ionic conductivity of potassium antimonate tungstates with partial Na+ or Li+ substitution for K+

We have studied the formation of monovalent metal antimonate tungstates by solid-state reactions in the xM₂CO₃ · (y ? x)K₂CO₃ · ySb₂O₃ · 2(2 ? y)WO₃ (M = Na, Li; 0 ≤ x ≤ y; 1.0 ≤ y ≤ 2.0) systems and identified the stability regions of pyrochlore phases at a temperature of 1123 K in the KSbO₃-WO₃-MSbO₃ (M = Na, Li) composition triangles. A model has been proposed for the ion distribution over the sites of the pyrochlore structure (sp. gr. Fd3m). The conductivity of the monovalent metal antimonate tungstates has been measured in the temperature range 500–1000 K, and a relationship between their ionic conductivity and structure has been established.