高精度散射光度滴定法测定苯妥英钠

用高精度散射光度滴定法测定苯妥英钠的含量。以 2 %糊精溶液作为胶体保护剂 ,用硝酸银标准溶液滴定苯妥英钠 ,生成沉淀的溶度积常数小 (Ksp=3× 10 -10 ) ,滴定曲线尖锐 ,可以准确判断滴定终点。高精度散射光度滴定法、重量法和电位滴定法测得苯妥英钠的含量分别为 98.82 %、98.72 %和 98.75 %。F检验和t检验结果显示高精度散射光度滴定法测定苯妥英钠 ,在精密度和准确度方面与重量法、电位滴定法测定结果均无显著差异 (α >0 .0 5 )。     

醋酸酯淀粉高取代度的测定

淀粉的乙酰化改性是扩大其应用的一个重要手段。测定醋酸酯淀粉取代度 (DegreeofSubstitution ,简称DS)的方法通常有酸碱滴定法、紫外法、核磁共振法及衰减全反射法[1 ] 等 ,后 3种方法需建立标准曲线 ,要求有一系列取代度的样品 ,实验操作较困难。所以实验室更多采用酸碱滴定法。实验室多采用乙醇为溶剂进行醋酸酯淀粉高取代度的测定[1～3] 。这种方法的缺点是皂化时间需 48～ 72h ,并且高取代度醋酸酯淀粉的溶解性不理想。本文对酸碱滴定法测定醋酸酯淀粉高取代度溶剂选择进行了探讨 ,以期建立一种快速、准确地测定醋酸酯淀粉高取代度的…     

可见光光谱滴定法测定水中总硬度北大核心CSCD

提出了可见光光谱滴定法测定水中总硬度的方法。在整个滴定过程采用颜色真实测量体系替代人的感官判定,建立了光谱计量参数与试剂量的色变滴定曲线,用曲线上的突变峰标识滴定终点或结构变化点。可见光光谱滴定法可以克服感官滴定存在色评价条件不统一、操作人员个体生理条件不一致、无法量值溯源等困难,能实现测定的自动化。上述方法用于测定水质总硬度标准样品,结果显示测定值均在标准样品认定值的不确定度范围内。按照标准加入法对实际样品进行回收试验,回收率为99.7%~101%。分别采用可见光光谱滴定法和目视滴定法[即乙二胺四乙酸(EDTA)络合滴定法]测定8种水体样品的总硬度,配对t检验结果表明两种方法的测定结果无显著性差异。     

极弱酸碱的pH滴定法研究

ｐＨ滴定法是指酸碱滴定至某一指定ｐＨ值时，即可根据滴定剂浓度，用量及有关公式，计算被测物浓度或含量的方法。本文深入讨论了测定原理，方法和应用，对１０种不同极弱酸碱进行了大量测定，测定结果相对误差一般在０．２％左右，相对标准偏差在０．３％左右，达到化不。ｐＨ滴定法具有简便，价廉，快速和通用的优点，为直接滴定极弱酸碱和化学分析仪化开辟了新的途径。     

国家标准方法测定锌精矿中锌的不确定度评定

对沉淀分离EDTA滴定法测定锌精矿中锌含量的测量不确定度来源进行了分析,并对EDTA标准溶液的滴定度、试样的质量、滴定体积、测定过程随机误差等不确定度分量进行了分析和量化,合成标准不确定度和扩展不确定度分别为0.20%和0.40%。     

表面活性剂碱度测定方法的改进和验证

表面活性剂碱度的检测主要依照国标GB/T 7378-1996中的方法,使用手动滴定、依据指示剂来判断滴定终点.本文基于全自动电位滴定仪对国标方法进行了改进和验证,建立了表面活性剂碱度测定的光度滴定法和电位滴定法,并对两种改进方法进行了验证.改进后的方法分别根据光度电极和电位电极的突跃点来判断滴定终点,判断更准确,与国标方法的结果相一致,重复性RSD≤3.0％.在国标方法基础上改进的光度滴定法和电位滴定法,滴定体积控制精确、自动化程度高、重复性和准确性好,可作为国标方法的改进方法用于实际检测.     

直接测定法测定葡萄酒中糖含量操作条件的探讨

通过分析滴定温度、滴定碱度、热源温度、沸腾时间和滴定速度等操作条件，探讨了操作条件对直接滴定法测定葡萄酒中糖含量的影响，确定了最佳操作条件，提高了测定结果的准确度。     

酸碱滴定法测定锂硼合金中硼的不确定度评定

评定了酸碱滴定法测定锂硼合金中硼的测量不确定度。分析并确定了不确定度来源,对各不确定度分量进行了合理评估。结果表明,影响硼测量不确定度主要因素是测量的重复性、NaOH标准滴定溶液的浓度以及滴定试液时的体积。     

自动电位滴定法测定高纯氯化铵的纯度

建立自动电位滴定法测定高纯试剂氯化铵纯度的方法。以硝酸银标准滴定溶液作滴定剂,采用自动电位滴定仪测定高纯氯化铵的含量。测定结果的相对标准偏差为0.03%(n=6)。采用该法与化学滴定法对高纯氯化铵样品进行测定,两种方法的测定结果无显著性差异。该方法操作简便、快捷,自动化程度高,滴定终点判断敏锐,测定结果准确可靠。     

工业氰基乙酸乙酯酸度测定方法的对比

碱滴定法测定工业氰基乙酸乙酯的方法通常有3种方法的变化,其一滴定中用指示剂目测滴定终点;其二,用电位法指示滴定终点,滴定中采用自动电位滴定仪;其三,先用水或饱和氯化钠水溶液将试样中的酸萃取入水相中,然后用碱滴定法在水溶液中测定其酸度。对此3种方法的变化作了对比试验,结果表明,在第一种变化中,在所试验的10种指示剂中只有甲基红在终点时有明显的颜色变化,但作为整个方法,测定结果的误差较大;对第二种方法变化,即采用电位滴定法,在终点到达时其滴定曲线中产生明显的突跃,而且按此方法所测得结果精密度和准确度都很好,方法操作方便而快速;对第三种方法变化,经试验用饱和氯化钠溶液作萃取剂的效果较好。经分离后的测定结果与电位滴定法的结果基本吻合,但此方法操作过程长而繁琐。     

超声波辐射制备羧甲基壳聚糖

应用超声波辐射方法制备水溶性的羧甲基壳聚糖,利用胶体滴定法测定产物中羧基含量,探讨超声波作用下,反应时间、反应温度及反应物投料比对羧甲基化程度的影响。结果表明,在其它反应条件相同时,使用超声波辐射比使用机械搅拌提高羧甲基取代程度,反应时间缩短５ｈ。     

羟丙基三甲基氯化铵壳聚糖的制备及其吸湿、保湿性能

抑菌活性;羟丙基三甲基氯化铵壳聚糖的制备及其吸湿、保湿性能     

羧甲基壳聚糖制备中的溶剂影响及精制方法研究

研究了有机溶剂中两步法制取羧甲基壳聚糖的反应过程.采用有机溶剂溶胀、氢氧化钠碱化、氯乙酸改性、乙醇溶析等步骤制备了高取代度羧甲基壳聚糖.考察了碱用量、氯乙酸用量和有机溶剂类型三个因素对羧甲基壳聚糖取代度的影响.通过比较二甲基亚砜、异丙醇、丙酮和乙醇四种有机溶剂中壳聚糖羧甲基化取代度变化规律,分析了羧甲基化的机理.实验结...     

羧甲基壳聚糖对铅离子的吸附性能研究

本文研究羧甲基壳聚糖对Pb^2 的吸附作用,探讨反应时间,离子强度,溶液的PH值、羧甲基取代度,温度等因素对吸附性能的影响,结果表明羧基是吸附Pb^2 的主要活性基团,羧甲基壳聚糖对Pb^2 的饱和吸附量为3．1083mmol/g,吸附Pb^2 的能力比壳聚糖,水溶性低聚壳聚糖强。     

Synthesis,Characterization and Antioxidant Activity of Quaternized Carboxymethyl Chitosan Oligosaccharides

In order to determine the effect of quaternary ammonium groups and carboxymethyl groups of chitosan on antioxidant activity, nine quaternized carboxymethyl chitosan oligosaccharides (QCMCOs) were prepared from chitosan with chloroacetic acid and 2,3-epoxypropyltrimethyl ammoniumchloride as the modifying agent under microwave irradiation. The structures of QCMCOs were characterized by FT-IR, NMR, XRD and their Mw were detected by gel permeation chromatography (GPC). The thermal stability was evaluated by thermal gravimetric analysis (TGA), and their antioxidant activities were investigated including scavenging activity of superoxide and hydroxyl radical, reducing power and metal chelating ability. The results revealed that the introduction of quaternary ammonium groups and carboxymethyl groups decreased the crystallinity and the thermal stability of chitosan oligosaccharide (COS), and their antioxidant activities were closely related to the degree of substitution of quaternary ammonium groups and the carboxymethyl groups. This study provides important guidelines for developing new antioxidant agents.     

流动电位/胶体滴定法测定聚电解质电荷密度的研究

探讨了应用粒子电荷测定仪的流动电位判定胶体滴定终点的可行性。结果表明流动电位曲线能在样品浓度大于 0 .6× 1 0 - 5mol· L- 1的溶液中准确指示胶体滴定的终点 ,较常用指示剂邻甲胺兰的使用极限浓度低一个数量级。观察到由阳离子聚电质滴定阴离子聚电质能减少盐干扰的现象。叔胺型阳离子淀粉应在酸性下滴定     

羧甲基壳聚糖在果蔬保鲜中的应用研究进展

综述了羧甲基壳聚糖的特性及其在果蔬的涂膜保鲜中的应用研究进展,讨论了羧甲基壳聚糖的浓度、分子量、pH值、取代度对其特性的影响,介绍了羧甲基壳聚糖对果蔬的涂膜保鲜效果。本文对开发羧甲基壳聚糖在果蔬防腐保鲜方面的应用具有理论指导意义。     

Biodegradable hyaluronic acid/n-carboxyethyl chitosan/protein ternary complexes as implantable carriers for controlled protein release

An ampholytic N-carboxyethyl chitosan (CEC), with various isoelectric points (IPs), was synthesized by grafting acrylic acid on chitosan utilizing Michael's reaction. Compared to native chitosan, CEC has enhanced water solubility and dramatically accelerated enzymatic degradation; the rate of degradation is proportional to the degree of substitution (DS). The results from turbidimetric titration and fluorescence studies revealed that CEC formed complexes with either hyaluronic acid (HA) or bovine serum albumin (BSA) within a certain pH range. The HA/CEC/BSA ternary complexes could be prepared by colloid titration with quantitative yield and BSA entrapment. The rate of BSA release from the complexes was affected by pH, ionic strength, DS of CEC, and the molecular weight (MW) of HA. The endurance of BSA release from the complexes could be extended up to 20 d by formulating them with high-MW HA and CEC with low DS.BSA release profiles from HA/CEC-2/BSA complexes.     

Synthesis and characterization of amphiphatic carboxymethyl-hexanoyl chitosan hydrogel: water-retention ability and drug encapsulation

Carboxymethyl-hexanoyl chitosan (NOCHC) amphiphatic hydrogel with excellent water-absorption and water-retention abilities under neutral conditions was successfully synthesized for the first time and then employed as a carrier for delivering amphiphatic agents. NOCHC is a water-soluble chitosan derivative bearing the carboxymethyl (hydrophilic) group and the hexanoyl (hydrophobic) group, which was synthesized using N,O-carboxymethyl chitosan (NOCC) as the starting precursor. Water-absorption ability (W(c)), water-retention ability, and drug encapsulation efficiency of the NOCHC hydrogel were investigated in terms of the degree of carboxymethyl and hexanoyl substitution. It was found that the amount of moisture uptake was dependent on the relative humidity as well as degree and nature of such substitution. The hexanoyl substitution affected significantly the water-absorption ability by altering the number of water-binding sites and the state of water under low humidity and the fully swollen state, respectively. In addition, the presence of hydrophobic hexanoyl substitution significantly retards water mobility during deswelling, causing better water-retention ability. Moreover, compared with that of pristine chitosan and NOCC, the encapsulation efficiency of ibuprofen (partially hydrophobic agent) was significantly enhanced with the incorporation of the hexanoyl group. These results demonstrate that the newly developed NOCHC amphiphatic hydrogel showed enhanced water-absorption ability, water-retention ability, and amphiphatic drug encapsulation efficiency compared with NOCC and chitosan.     

Determination of cationic polyelectrolytes using a photometric titration with crystal violet as a color indicator

The reaction of the cationic dye, crystal violet (CV) with the anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) results in a decrease of the absorbance of CV at the maximum absorption wavelength (590 nm). This change of the absorption spectra of the CV has been already applied to the determination of anionic polyelectrolytes using flow injection analysis method. In this paper, CV was applied to the indicator for the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by photometric titration, using a PVSK solution as a titrant. The end-point of the titration is detected as the break point of the titration curve. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 0 to 5×10⁻⁵ eq. mol dm⁻³ for Cat-floc, glycol chitosan and methylglycol chitosan. The effects of the concentration of CV and coexisting electrolytes in the sample solution and the effect of pH of the sample solution on the degree of the change of absorbance at the end-point were also examined.