Determination of thiabendazole residues in potatoes using high pressure liquid chromatography

Summary This paper describes a method for the extraction, purification and quantification by high pressure liquid chromatography using fluorimetric detection, of thiabendazole residues from potatoes. Bonded silica sorbent extraction columns (diol phase) are used for sample clean up, resulting in a rapid and accurate analysis. The average recovery was 93.8%±2.1%. Levels of about 0.0004μg of TBZ, equivalent to 0.033 mg kg⁻¹ in potatoes (on fresh weight basis), were readily detected from deliberately contaminted potatoes.     

Ultra-fast separation of wheat glutenin subunits by reversed-phase HPLC using a superficially porous silica-based column

A relatively new, unique column packing material for reversed-phase high-performance liquid chromatography (RP-HPLC) was evaluated for rapid separation of wheat glutenin protein subunits. The product named “Poroshell” by the manufacturer consists of a solid core and a porous coat instead of solid silica spheres used in conventional RP-HPLC column packing. This architecture favours rapid mass transfer, facilitating faster reversed-phase separations of biomolecules compared to conventional silica columns. The main objective of this study was to evaluate the quality of separations of glutenin subunits (GS), as well as to optimize conditions to produce the fastest possible run times without sacrificing resolution using a Poroshell 300SB-C₈ 2.1×75 mm column. The stability of GS separations over time was also assessed. Two different bread wheat genotypes were used for optimization of separation conditions and six more common and durum wheat genotypes possessing different subunit combinations were used for further evaluation. Glutenin protein was extracted with 0.08 M Tris–HCl buffer (pH 7.5) containing 50% 1-propanol under reducing conditions after pre-extraction of soluble proteins with 50% 1-propanol. Optimization of GS resolution and sample throughput by RP-HPLC was assessed in response to variation in eluent flow rate, acetonitrile (ACN) gradient, and column temperature. The best resolution of both HMW- and LMW-GS was obtained in 13 min using a 23–44% ACN gradient with a flow rate of 0.7 mL/min at 65 °C. Subunit elution times and integrated areas were highly repeatable even after several hundred injections. Highly satisfactory separation of HMW-GS and quantification of ratio of HMW- to LMW-GS were achieved in less than 4 min per sample using a modified HPLC gradient. Ratio of HMW- to LMW-GS was unaffected by the speed of the separations. As well, the elution order of HMW- and LMW-GS was unaffected by the rapid analysis, compared to conventional RP-HPLC separations, so no new learning was required for interpreting chromatograms and classification of subunits. The rapid RP-HPLC method using the Poroshell column appears to be very well suited for routine quantification of HMW-GS and LMW-GS especially for purposes of wheat quality screening and wheat cultivar development activities where large numbers of samples are typically encountered.     

SILICON ACCUMULATION AND ITS INFLUENCE ON SOME OF THE LEAF CHARACTERISTICS,MEMBRANE STABILITY AND YIELD IN RICE HYBRIDS AND VARIETIES GROWN UNDER AEROBIC CONDITIONS

Efforts to minimize water use in rice cultivation and stress tolerance are important in the present climate change scenario. Silica solubilizers might help in understanding the tolerance of plants to water deficit conditions or aerobic conditions. Rice cultivation in combination with silica was applied in the form of fertilizers (sodium silicate) and solubilizers (Imidazole and glycine) was studied in experimental farm and also in farmer's field. The varieties used were ‘KrishnaHamsa' (KH), ‘Rasi', ‘Jaya', hybrids ‘PA-6201' and ‘PHB-71' under aerobic conditions both in wet (Kharif) and dry (rabi) seasons. Transmission electron microscopy in this study provided evidence that silicon was deposited in the epidermal cell wall and the intercellular space of the silicon-treated rice leaves. The epidermal cell wall accumulation was absent in the control plants. Genotypic variation and treatment influences were observed for relative water content and cell membrane stability. Among the different rice cultivars ‘Rasi' followed by ‘PHB-71' and PA- 6201, were able to maintain cell membrane stability and chlorophyll content. Leaf rolling, chlorophyll, relative water contents, and dark adapted chlorophyll fluorescence were superior under aerobic conditions with application of solubilizers. However, significant differences in stomatal conductance were seen between seasons and genotypes. The silicon treated plants were able to maintain similar yields under aerobic conditions also as that of irrigated controls.     

Silicon uptake by wheat: Effects of Si pools and pH

Silicon (Si), although not considered essential, has beneficial effects on plant growth which are mostly associated with the ability to accumulate amorphous (phytogenic) Si, e.g., as phytoliths. Phytogenic Si is the most active Si pool in the soil–plant system because of its great surface‐to‐volume ratio, amorphous structure, and high water solubility. Despite the high abundance of Si in terrestrial biogeosystems and its importance, e.g., for the global C cycle, little is known about Si fluxes between soil and plants and Si pools used by plants. This study aims at elucidating the contribution of various soil Si pools to Si uptake by wheat. As pH affects dissolution of Si pools and Si uptake by plants, the effect of pH (4.5 and 7) was evaluated. Wheat was grown on Si‐free pellets mixed with one of the following Si pools: quartz sand (crystalline), anorthite powder (crystalline), or silica gel (amorphous). Silicon content was measured in aboveground biomass, roots, and soil solution 4 times in intervals of 7 d. At pH 4.5, plants grew best on anorthite, but pH did not significantly affect Si‐uptake rates. Total Si contents in plant biomass were significantly higher in the silica‐gel treatment compared to all other treatments, with up to 26 mg g^–1 in aboveground biomass and up to 17 mg g^–1 in roots. Thus, Si uptake depends on the conversion of Si into plant‐available silicic acid. This conversion occurs too slowly for crystalline Si phases, therefore Si uptake from treatments with quartz sand and anorthite did not differ from the control. For plants grown on silica gel, real Si‐uptake rates were higher than the theoretical value calculated based on water transpiration. This implies that Si uptake by wheat is driven not only by passive water flux but also by active transporters, depending on Si concentration in the aqueous phase, thus on type of Si pool. These results show that Si uptake by plants as well as plant growth are significantly affected by the type of Si pool and factors controlling its solubility.     

基于亚甲基蓝二氧化硅纳米颗粒的细胞与活体成像

采用反相微乳液法,制备了以亚甲基蓝为内核材料的亚甲基蓝二氧化硅纳米颗粒,通过优化亚甲基蓝的包裹浓度获得荧光信号较强的纳米颗粒,并初步考察了其用于Hela细胞标记与体内示踪的可行性.通过MTT实验考察了颗粒对细胞的毒性影响以及较为适宜的标记细胞的浓度,结果表明:当颗粒浓度为1 mg/mL时,细胞的存活率仍有80%左右.利用激光共聚焦显微镜考察了Hela细胞对颗粒的吞噬情况以及颗粒在细胞内的分布情况,结果表明,该颗粒能被Hela细胞吞噬且主要分布在溶酶体内.活体荧光成像结果显示,尾静脉注射该颗粒后,裸鼠全身都发射出近红外荧光信号,随着血液的循环,颗粒慢慢聚集在肝脏等器官中.以上结果表明,包裹亚甲基蓝的二氧化硅纳米颗粒可以用于细胞的标记和体内示踪成像.     

中空介孔二氧化硅微球的制备及表征分析

以二氯化-N,N'-二(3-氢化松香酰氧-2-羟丙基)四甲基乙二胺(DHRT)为模板剂,正硅酸乙酯为硅源,采用溶胶-凝胶和水热合成的方法,分别制备了中空介孔二氧化硅微球SiO2-1和SiO2-2.利用SEM、TEM、FT-IR、XRD和氮气吸附-脱附对SiO2-1和SiO2-2进行表征分析,结果表明:两种方法均已成功制...     

钴离子改性的介孔TiO_2抗菌性能研究

[目的]开发不需要人造光源和太阳光直射激发的,以及改性离子不易泄漏的新型无机抑菌材料。[方法]合成金属离子Co改性的锐钛矿型二氧化钛介孔材料,并用N2解析付仪、XRD进行表征,确认其结构。在无紫外光和人造光源直射的条件下,对材料进行抑菌性能以及细菌吸附研究。[结果]抑菌试验表明这种材料在无紫外光和人造光源直射条件下对大肠杆菌有一定抑制作用和吸附作用。[结论]该研究对其他金属离子改性的抑菌介孔材料的研究有一定的借鉴作用。     

功能化二氧化硅固载七钼酸盐催化葡萄糖差向异构反应

采用硅烷偶联剂改性硅载体锚链Mo7O2-4的方法制备了8种固载型催化剂,以D-葡萄糖水相差向异构化制备D-甘露糖反应,评价了催化剂的催化性能,并通过ICP和UV-vis对催化剂的稳定性进行了表征。结果表明,正辛基及十二烷基硅烷修饰的SiO2催化剂（C4、C8）具有较高的催化活性和稳定性,在反应温度80℃、初始pH 4~5的条件下反应6 h,D-甘露糖质量收率分别为28.0%和27.2%。     

仿生物矿化制备硅纳米材料

利用正硅酸乙酯和人工合成的多肽,在比较温和的条件下快速合成了硅纳米材料,并研究了制备过程中的多种因素对产物形貌的影响,研究发现：在pH值=8．0的磷酸盐缓冲液中,当R5肽的浓度为10mg／mL,正硅酸乙酯的浓度0．1mol／L,反应15min时,可得到规则的球状颗粒。X射线能谱分析证明产物为硅和多肽的复合物。     

木纤维/气相SiO2复合真空绝热板的制备与表征

【目的】分析木纤维用量对木纤维/气相SiO_2复合真空绝热板(vacuum insulation panel,VIP)性能的影响,为复合VIP的制备提供支持。【方法】采用中密度纤维板生产过程中所使用的木纤维与气相SiO_2进行复合,通过模压成型法制成木纤维/气相SiO_2多尺度结构复合芯材,并将其真空封装制备木纤维/气相SiO_2复合真空绝热板(VIP)。通过场发射扫描电子显微镜(SEM)、压汞仪和傅里叶红外光谱分析仪(FTIR),研究不同木纤维用量对复合VIP芯材的微观形貌、孔隙结构和辐射导热的影响,并利用热流法导热仪测试了复合VIP在不同环境温度下的导热系数。【结果】大部分的木纤维空隙、纹孔内都填充满了气相SiO_2纳米级粉末,并且搭建起由木纤维和SiO_2构建的三维空间结构网络;当木纤维质量分数为40%时,VIP的总孔体积为4.61 cm~3/g,孔隙率为60.6%,平均孔径为0.13μm;当环境温度为25℃时,VIP辐射导热系数为0.60 mW/(m·K),总导热系数为6.58 mW/(m·K),而当环境温度升至55℃时,总导热系数为7.21 mW/(m·K),相比于未添加木纤维的气相SiO_2芯材,综合性能成本降低了28.7%。【结论】利用木纤维替代部分气相SiO_2制备复合VIP能够大大降低芯材成本,并且还能保持良好的隔热性能,具有十分广泛的应用前景。