中性氧化铝柱净化-UPLC-MS/MS法测定乳和乳制品中黄曲霉毒素M_1

建立了中性氧化铝固相萃取柱净化,超高效液相色谱-串联质谱法(UPLC-MS/MS)测定乳和乳制品中黄曲霉毒素M1的分析方法。样品经乙腈提取,乙酸锌辅助沉淀蛋白,中性氧化铝SPE柱净化,以乙腈和0.1%甲酸水溶液作为流动相进行梯度洗脱,以电喷雾离子源(ESI)在正离子多反应监测(MRM)模式下进行测定,外标法定量。结果表明,黄曲霉毒素M1在0.1~50μg/L浓度范围内呈良好的线性关系,相关系数(r2)大于0.99;空白样品加标回收率在70.8%~79.2%之间,相对标准偏差小于8%。方法检出限为0.02μg/kg,定量限为0.05μg/kg。该方法实用、准确、灵敏,适用于乳和乳制品中黄曲霉毒素M1的测定。     

高效液相色谱-串联质谱法测定水产品中黄曲霉毒素G2、G1、B2、B1

建立了用高效液相色谱-串联质谱法（HPLC-MS/MS）测定水产品中黄曲霉毒素G2、G1、B2、B1残留量的方法。84%甲醇水溶液提取水产品中4种黄曲霉毒素,正己烷脱脂,HLB固相萃取柱净化。采用电喷雾电离,正离子扫描,选择多反应检测模式（MRM）监测,外标法定量。该法对4种黄曲霉毒素标准曲线的线性回归系数均在0.99以上,黄曲霉毒素G1、B1方法定量限为0.5μg/kg,G2、B2方法定量限为0.3μg/kg。4种黄曲霉毒素的回收率为56%～80%,相对标准偏差1.58%～14.4%。该法灵敏,结果可靠,可用于水产品中黄曲霉毒素的测定。     

婴幼儿谷类辅助食品中黄曲霉毒素B1和M1残留量的测定

建立用MycoSepTM净化柱和高效液相色谱法测定婴幼儿谷类辅助食品中黄曲霉毒素B1和M1残留量。样品经乙腈∶水(体积比84∶16)提取,提取液通过MycoSepTM226柱净化、浓缩,三氟乙酸和正己烷进行衍生化,C18色谱柱分离,荧光检测器检测,外标法定量。实验表明,黄曲霉毒素在1.25~12.5 ng/mL线性关系良好(r≥0.999),在有机燕麦粉和有机多种谷粉中分别添加1.0μg/kg和2.0μg/kg进行加标回收试验,回收率为84.6%~103.9%,相对标准偏差为1.0%~6.0%,黄曲霉毒素B1、M1最低检测限均为0.05μg/kg和0.08μg/kg。此方法不仅定量准确,精密度高且操作方便,同时也适合黄曲霉毒素G1、B2、G2、M2的测定。     

蔬菜和水果中59种农药残留同时检测-超高效液相色谱串联质谱法

建立了一种同时测定蔬菜和水果中59种农药残留的超高效液相色谱串联质谱检测方法。样品经1%醋酸乙腈溶液提取,震荡离心后经Qu ECh ERS试剂盒净化,UPLC-MS/MS法同时定性、定量测定蔬菜和水果中59种农药残留。59种农药在5~500 ng/m L范围内线性关系良好,相关系数(r)均大于0.99;以5,10,50μg/kg 3个浓度水平进行添加回收实验,59种农药的平均回收率在60.5%~109.7%之间,相对标准偏差为2.6%~17.1%,方法的检出限为0.01~0.80μg/kg。方法重现性、灵敏度高、分析时间短、确证能力强,适用于蔬菜和水果中59种农药残留的同时检测。     

QuEChERS-超高效液相色谱-串联质谱法测定化妆品中禁用物质多菌灵的含量

建立了化妆品中禁用物质多菌灵的QuEChERS-超高效液相色谱-串联质谱(UPLC-MS/MS)的检测方法。样品中的多菌灵经体积分数1%乙酸-乙腈溶液提取和Qu Ech ERS法净化后,C18色谱柱分离,采用UPLC-MS/MS电喷雾电离(ESI)、正离子、多反应监测(MRM)模式检测,外标法定量。多菌灵的测定线性范围为10~100 ng/m L,线性相关系数r大于0.99,方法检出限为10μg/kg,在不同添加浓度下的回收率范围为83.1%~102.7%,相对标准偏差(n=6)小于10%。     

液相色谱-串联质谱法测定卷烟中的黄曲霉素

建立了高效液相色谱-串联质谱(LC-MS/MS)同时检测烟草中黄曲霉毒素B1、B2、G1、G2的方法,优化了液相色谱条件和质谱的相关参数。待测样品经研磨成粉末后,直接经三氯甲烷提取,SPE固相萃取柱净化,用乙酸铵-甲醇(10mmol/L乙酸铵)梯度洗脱,选择电喷雾离子源(ESI),正离子扫描多反应监测(MRM)模式,外标法定量。结果表明,4种黄曲霉素的定量限均低于0.04μg/kg,加标回收率在66.3%~93.3%,相对标准偏差(RSD)为5.8%~15.5%。方法快速简便,适合烟草中黄曲霉素的准确测定。     

高效液相色谱柱后衍生法测定中药材中的黄曲霉毒素

检测普洱城区僵蚕、陈皮、桃仁、胖大海4种中药材的黄曲霉毒素,了解其污染状况。样品经70%甲醇提取、免疫亲和柱净化后,用HPLC-柱后衍生-荧光检测器进行分析测定药材中的黄曲霉毒素(G2、G1、B2、B1)含量。检测的80个样品中,共有7个样品检出黄曲霉毒素,黄曲霉毒素B1的含量最高为1.89μg/kg,黄曲霉毒素总量最高为3.57μg/kg。尽管未超出国家药典规定范围,但是普洱城区4种中药材存在一定的黄曲霉毒素污染的风险。     

UPLC-MS/MS法测定牛奶中普鲁卡因青霉素G残留量

建立一种UPLC-MS/MS法(超高压液相色谱-串联质谱法)测定牛奶中普鲁卡因青霉素G的快速方法。采用正离子电离模式和MRM扫描模式。设置1.0,3.0,5.0μg/kg 3个加标水平,测定加标回收率。结果表明利用UPLC-MS/MS检测的普鲁卡因青霉素G在1.0~20.0 ng/m L的浓度范围内呈良好线性关系。3个加标水平的加标回收率为94.6~101.1%,相对标准偏差为1.3%~2.1%,检出限为1.0μg/kg。该方法快速,灵敏,准确,可满足普鲁卡因青霉素G残留量的测定。     

桑葚中烯酰吗啉残留量测定

建立了检测桑葚中烯酰吗啉残留量的超高效液相色谱-串联质谱(UPLC-MS/MS)方法。桑葚样品经乙腈提取,石墨化炭黑/氨基复合柱(Carbon/NH_2)净化,以0.1%甲酸甲醇溶液+0.1%甲酸水溶液+0.1%甲酸乙腈溶液为流动相进行梯度洗脱,采用电喷雾正离子模式,多反应监测方式进行采集,外标法定量。烯酰吗啉在桑葚中的检测限为0.25μg/kg,定量限为1.00μg/kg。在1.00~50.00μg/L质量浓度范围内,方法线性关系良好,相关系数(R~2)为0.999;方法的回收率(92.18%~104.39%)和精密度(3.48%~5.13%)均满足定量分析要求。该方法适用于桑葚中烯酰吗啉残留量的测定。     

超高效液相色谱串联质谱法测定鸡肉中噻节因残留

建立鸡肉中噻节因的超高效液相色谱串联质谱(UPLC-MS/MS)残留测定方法。鸡肉样品选用乙腈提取,采用UPLC-MS/MS多反应模式(MRM)进行分析测定。噻节因添加质量在0.2~10μg范围内,方法平均回收率为87.6%~101.6%,相对标准偏差为2.44%~5.90%。方法的最小检出量为0.005 mg/L,最低检测浓度为0.01 mg/kg。该方法简单、准确,重复性较好,适用于禽蛋中噻节因的残留检测。     

Polymorphism of LiGa5O8 and of LiGa5O8-MgGa2O4Solid Solutions

High-temperature X-ray diffraction and differential thermal analyses showed that LiGa₅O₈ exists in two polymorphs related by the first-order transition at 1138°±3°C of the low-temperature simple-cubic form, space group (probably) O⁷, to the high-temperature spinel (fcc) form, space group O _h ⁷. The transition is rapid, and the high-temperature form in pure LiGa₅O₈ could not be quenched to room temperature under the conditions used. However, the high-temperature polymorph can be quenched under equilibrium conditions when 40 mol% or more MgGa₂O₄ is present. The subsolidus equilibrium relations in the system MgGa₂O₄-LiGa₅O₈ are discussed.     

Magnetoresistance of CuxCo1-xFe2O4 Ferrites

Magnetoresistance measurements (Δ/R) were carried out on Cu _x Co_{1- x} Fe₂O₄ samples with x =1, 0.75, 0.50, 0.25 and cobalt ferrite in the range of magnetic intensity (H) from 1.0 to 4.5 kG. Linear plots were obtained between log (Δ/R) and log H for all compositions except that of cobalt ferrite. The values of n at x =0.5 do not agree with the results of some authors. The discrepancy may be attributed to the value of magnetic field intensity at which such measurements were carried out. The similarity of features of n and μ_D with composition leads us to believe that the magnetoresistance may arise from the scattering of conduction electrons by localized electrons involving the s-d exchange interaction.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Expansive properties of the mixture C4ASH12 − 2CS III. Effects of temperature and restraint

The effects of temperature and restraint upon the hydration and the expansion of $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}\text{? 2}\text{C}\text{S}$ mixture compacts in different contact solutions have been investigated. Temperatures above 20°C do apparently hinder the formation of an impervious felt-like layer of ettringite around the $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}$ particles, thus greatly reducing the retarding effect of the lime. An uniaxial restraint of 1 Kg/cm² is enough to reduce sensibly the expansions which remain however high (about 100%). The results can be satisfactorily interpreted by the reaction and expansion mechanism hypothesized in our previous papers.     

Raman Study of Glasses of Ba2TiSi2O8 and Ba2TiGe2O8

Raman spectra are reported for fresnoite (Ba₂Ti(Si,Ge)₂O₈ glasses, and comparison is made between the Raman spectra of the corresponding crystalline powders and glasses of Ba₂TiSi₂O₈ and Ba₂TiGe₂O₈. The Ba₂TiGe₂O₈ glass spectra show correspondence with the Ba₂TiGe₂O₈ crystalline Raman spectra; the v _s(Ge–O–Ge) mode occurs at 518 cm⁻¹ in the glass and at 521 cm⁻¹ in the crystalline material. Five-fold coordinated titanium is the majority species present in the Ba₂TiGe₂O₈ glass as revealed by a strong band at 824 cm⁻¹ in the I glass spectrum. The Ba₂TiSi₂O₈ glass spectra are similar to the Ba₂TiSi₂O₈ crystalline spectrum; the strongest band is found at 836 cm⁻¹ in the I glass spectrum. Through comparison with the previous Raman data of other titania silicate glasses, we conclude that the Ba₂TiSi₂O₈ glass has a structure similar to the crystalline phase.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Effects of metal-support interactions on the hydrogenation of CO over PdSiO2 and PdLa2O3

A study of CO hydrogenation over $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$ has been carried out for the purpose of identifying the effects of Pd dispersion, Pd morphology, and support composition on the catalytic activity of supported Pd. The specific activity of each catalyst for methanol and methane synthesis was determined from microreactor studies carried out at a fixed set of reaction conditions. Palladium dispersion was measured by H₂O₂ titration, and the morphology of the Pd crystallites, as expressed by the distribution of Pd(100) and Pd(111) planes, was determined from in situ infrared spectra of adsorbed CO. The crystallite morphology of the $\text{Pd}\text{SiO}{}_2$ catalysts is the same, independent of Pd weight loading: 90% of the surface is comprised of Pd(100) planes and 10% of the surface is comprised of Pd(111) planes. By contrast, the crystallite morphology of the $\text{Pd}\text{La}{}_2\text{O}{}_3$ catalysts changes with Pd loading. Primarily Pd(100) planes are exposed at low-weight loadings while Pd(111) planes are exposed at high-weight loadings. The Pd dispersion has little effect on the methanol turnover frequency over both $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$, for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over $\text{Pd}\text{SiO}{}_2$, but increases with decreasing dispersion over $\text{Pd}\text{La}{}_2\text{O}{}_3$. It is further observed that the Pd morphology influences the specific activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ is a factor of 7.5 greater than that of $\text{Pd}\text{SiO}{}_2$.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.