Microwave promoted methylation of plant polysaccharides

O-Methylation is of outstanding importance in structural polysaccharide chemistry. A novel method for the methylation of polysaccharides using microwave (MW) irradiation is described. Seed gum from Cyamopsis tetragonolobus (Guar) was fully methylated with dimethyl sulphate and sodium hydroxide using 100% microwave power for 4 min in 68% yield. The completely methylated seed gum thus obtained was hydrolyzed by 70% formic acid followed by 0.5N H₂SO₄ under full microwave power for 1.16 and 1.66 min, respectively. The partially methylated monosaccharides were separated and identified.     

Synthesis and characterization of guar gum‐graft‐polyacrylonitrile

Cerium(IV) mediated grafting of polyacrylonitrile on to guar gum was studied. Grafting parameters were studied gravimetrically, as a function of temperature, initiator concentration and Guar to acrylonitrile ratio. Higher temperatures resulted in higher monomer conversion and homopolymer formation. Both monomer conversion and extent of grafting increased with increase in cerium ion concentration in the range studied (0.91–9.12 mmol/l). Similar results were obtained with increase in monomer to guar gum ratio from 1 to 5. Grafting with this initiator was found to be generally good with high grafting efficiencies and low homopolymer formation for most experiments. The copolymers obtained were subjected to alkaline hydrolysis to convert nitrile groups in to carboxylic acid groups and the water absorbency of the resulting anionic guar gum was studied. Materials with water absorption up to 300 g/g could be obtained from this study. Copyright © 2003 John Wiley & Sons, Ltd.     

超高灵敏显色反应测定痕量锑──锑（Ⅲ）─罗丹明B─碘化钾体系

本文研究结果表明，水溶性大分子化合物阿拉伯胶和非离子表面活性剂ＴｒｉｔｏｎＸ－１００共同存在下，锑碘配阴离子和罗丹明Ｂ的显色反应具有很高的灵敏度。缔合物的最大吸收在５ｇ０ｎｍ，摩尔吸光系数ε＝６．１×１０￣５Ｌ·ｍｏｌ－１·ｃｍ－１。用巯基棉富集锑，分离干扰离子。本法可应用于有色金属中痕量锑的测定。     

两性田菁胶在处理生活污水中的助凝作用

研究了以聚合硫酸铁为主凝剂、两性田菁胶(ASG)为助凝剂处理城市生活废水的各种影响因素.实验结果表明:聚合硫酸铁和两性田菁胶分别以200mg/L和10mg/L的复配浓度、pH值接近7时混凝效果最佳,CODCr去除率达到近80%,处理后废水CODCr达到国家排放标准.     

Improvement of the electrophoretic protein profiles of Leguminosae gums extracts using gamanase and application to the evaluation of carob-guar mixtures

A quantitative assay for guar gum in carob gum, based on the extraction of proteins in acetonitrile-water (7:3), separation by capillary electrophoresis and multiple linear regression (MLR) using the areas of nine selected peaks as predictors, was improved by performing the extraction in the presence of gamanase. In the absence of the enzyme, peak migration times and areas depended on the guar content, which complicated peak identification and evaluation. Manual correction of the migration times by comparison with standard electropherograms obtained with pure carob and carob-guar mixtures was required; however, when the proteins were extracted under sonication at 60 °C for 30 min in the presence of gamanase, the migration times and peak areas did not vary with the composition of the carob-guar mixtures, and its reproducibility improved largely. These effects were attributed to the reduction of the viscosity of the extracts and the removal of the galactomannose interactions with the proteins and the capillary walls. Peak identification and evaluation were easily and directly performed on these electropherograms without further processing. An MLR model constructed with 36 carob-guar mixtures containing up to 20% guar, and by measuring the areas of 12 selected peaks and using eight of them as predictors, yielded a detection limit of 2.8% guar (α=β=0.05 criterion). A model of similar quality was obtained by partial least-squares (PLS) regression.     

Superoxes,high temperature universal phases in (GC)2

Most of the common classes of organic compounds chromatograph normally on Superoxes. There is no tailing or adverse effect from excessively different activity different activity coefficients. Superoxes are therefore universal phases for gas chromatography. This is also expressed by a wide useful temperature range from ～50° to ～300°. High MW Superox-4 has a MAOT about 20° higher than the lower MW Superox-0.1. Several applications illustrating the versatility of Superox phases in (GC)² are presented.     

Graft copolymerisation of acrylamide onto cashew gum

The synthesis of cashew gum-g-polyacrylamide was carried out at 60 °C by a radical polymerisation using potassium persulphate as the redox initiator under N₂ atmosphere. A series of graft copolymers, varying in acrylamide concentration and keeping the concentration of the initiator and polysaccharide constant, was prepared. These graft copolymers were characterised by elemental analysis, infrared and ¹³C NMR spectroscopy, rheological studies, differential scanning calorimetry and thermogravimetric analysis. Comparisons amongst grafting parameters of the reaction of various natural polysaccharides with polyacrylamide (PAM) were carried out. High percentages of acrylamide conversion (%C) and grafting efficiency (%E) were obtained for cashew gum (CG), even with a low acrylamide/gum ratio. All copolymers had intrinsic viscosity and thus the hydrodynamic volume much higher than the CG value and closer to the PAM. The CG-g-PAM solution had an absolute viscosity at 2.5% concentration (wt./vol.) up to 33 and 3.3 times the CG and PAM values, respectively. Grafting of PAM chains onto the polysaccharide enhances its thermal stability.     

Effect of environmental factors and carbohydrate on gellan gum production

Submerged culture fermentation studies were carried out in batch mode for optimizing the environmental parameters and carbon source requirement by Pseudomonas elodea for the production of gellan gum. The maximum production of gellan gum was obtained with 16-h-old culture and 8% inoculum at 30°C and pH 7.0 after 52 h of incubation (6.0 g/L). Of the various carbon sources tested, 2% sucrose, glucose, and soluble starch yielded considerably high amounts of gellan. Studies on the concentration of various carbohydrates on gellan gum production indicated that the optimum concentration of glucose and starch was 3%, whereas for sucrose it was 4%. The addition of glucose in the medium above 3% had a detrimental effect on gellan yield. The investigation of intermediate two-step addition of glucose under identical conditions of fermentation showed an enhanced production of gellan (8.12 g/L) as compared with the control (6.0 g/L). To optimize the recovery of gellan from fermented broth, different solvents were tested for precipitation of gellan gum. Among the various solvents tested, tetrahydrofuran gave better recovery of gellan (82%) as compared with the conventional solvent isopropanol (49%).     

季铵盐水处理剂对A_3钢在模拟油田废水中的缓蚀行为

以一种植物胶与喹啉和吖啶进行反应,试制得具有缓蚀-杀菌功能的阳离子型水处理剂FQ-C、FA-C.这类聚氮杂环季铵盐因含π电子,一方面能在铁表面引起π电子吸附,形成化学吸附膜,起到缓蚀作用;另一方面因含季铵基因而具有杀灭硫酸盐还原菌(SRB)的功能.通过测定这类季铵盐对A_3钢在模拟油田废水中的缓蚀效果,并用X射线衍射等研究方法,证明了试制药剂能有效抑制SRB引起的腐蚀,且药的缓蚀性能与杀菌性能之间有协同作用.     

用均匀设计法优化瓜尔豆愈伤组织诱导的研究

以瓜尔豆子叶和下胚轴为外植体，采用均匀设计法，研究了基本培养基、激素水平、蔗糖浓度和活性炭对愈伤组织形成的影响。通过建立模型表明，瓜尔豆子叶形成愈伤组织的能力高于下胚轴；2，4-D和蔗糖浓度在一定范围内对愈伤组织的形成呈正相关性作用，且外植体、2，4-D和KT浓度三者之间存在很强的交互作用；而活性炭对愈伤组织形成未表现出明显作用。