线性电位滴定法测定壳聚糖的脱乙酰度

采用线性电位滴定法测定壳聚糖的脱乙酰度,并与酸碱指示剂滴定法测定的结果进行比较,结果表明线性电位滴定法测定比较适合粘度高的样品,且分析速度快,操作简单,精密度高。     

壳聚糖脱乙酰度测定方法的比较

比较并分析壳聚糖脱乙酰度的两种测定方法。通过一组正交试验来制备不同脱乙酰度的壳聚糖,同时采用碱量法和紫外分光光度法进行脱乙酰的测定。分别从测定的原理和影响因素进行比较分析并进行测定结果的t检验。碱量法操作简便,但干扰因素多,结果重现性差;紫外分光光度法干扰因素少,客观、准确,结果重现性好。两种方法测定的结果存在一定差异。     

红外光谱法测定壳聚糖脱乙酰度

以碱量法为对比方法,考察了基于A1655／A3450和A1320／A1420的2种红外光谱计算壳聚糖脱乙酰度方法的准确性。结果表明,红外光谱法虽精密度低于碱量法,但基于A1655／A3450的红外测试结果与碱量法基本相吻合;基于A1320／A1420加的红外光谱计算结果略高于碱量法,与商家标注值相吻合,且不受样品含少量水、残酸或残碱的影响。红外光谱法是一种较为理想的壳聚糖脱乙酰度测定方法,同时采用A1655／A3450和A1320／A1420计算更利于得到准确的测定结果。     

直接测定壳聚糖脱乙酰度分析方法的比较

分别采用差示扫描量热法与红外吸收光谱法直接测定壳聚糖脱乙酰度,试验表明选择差示扫描量热曲线295℃处放热分解峰峰面积作为计算参数的结果与红外吸收光谱中A1320/A1420计算结果无统计学显著性差异,同时两种分析方法操作简便,分析时间短,故可满足相关工业生产实时分析要求。     

双突跃电位滴定法测定壳聚糖脱乙酰度

用 Microsoft Excel研究了电位滴定法测定壳聚糖的脱乙酰度的滴定曲线 ,利用两个突跃之间的氢氧化钠的用量计算了脱乙酰度。该方法具有准确可靠 ,重复性好等优点 ,相对标准偏差小于 0 .9%。     

壳聚糖脱乙酰度的测定方法比较

通过比较酸碱滴定法,电位滴定法和紫外光谱法对壳聚糖脱乙酰度的测定结果,发现三种方法中的精确度为紫外光谱法电位滴定法酸碱滴定法,其中紫外光谱法因其准确性高且所需仪器简单,比其它方法更具优越性。     

高脱乙酰度壳聚糖的制备

以甲壳素为原料,以异丁醇为溶剂,氢氧化钠为亲核试剂,探讨了一种制备高脱乙酰度壳聚糖的新方法.研究了投料比、反应温度、反应时间、反应方法等对脱乙酰度的影响.结果表明,在反应温度为110℃,反应时间2.5h,壳聚糖∶NaOH∶醇=1∶5∶12(质量比)条件下制得脱乙酰度为93.2%的壳聚糖,而传统水溶剂脱乙酰度小于50%.另外间歇法处理样品可以在较短的时间里制备出脱乙酰度较高的壳聚糖,并用红外谱图对壳聚糖进行了表征.     

壳聚糖脱乙酰度测定方法研究新进展

主要介绍近年来壳聚糖脱乙酰度测定方法研究新进展,概述了双突跃电位滴定法——加酶预处理、光纤折射传感法、拉曼光谱法、库仑滴定法等测定原理与特点,并作出比较,为相关科学研究和工业生产测定方法的选择提供理论参考。     

壳聚糖脱乙酰度测定方法研究新进展

主要介绍近年来壳聚糖脱乙酰度测定方法研究新进展,概述了双突跃电位滴定法——加酶预处理、光纤折射传感法、拉曼光谱法、库仑滴定法等测定原理与特点,并作出比较,为相关科学研究和工业生产测定方法的选择提供理论参考。     

甲壳质制壳聚糖脱乙酰度条件研究

研究了甲壳质分步脱乙酰制壳聚糖反应的温度、时间、NaOH含量和预浸泡时间对脱乙酰度的影响.结果表明,最佳的反应温度为110℃,反应时间为4 h,NaOH的质量分数为47%,预浸泡时间为48 h.在此条件下,可以得到脱乙酰度90%以上的壳聚糖产品.     

Effect of degree of deacetylation of chitosan on the kinetics of ultrasonic degradation of chitosan

The objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003     

壳聚糖脱乙酰度测定方法的总结与比较

测定壳聚糖脱乙酰度(DD)的方法主要分为三类:①光谱法:紫外、红外光谱和核磁法;②破坏样品法:色谱法、差示扫描量热和元素分析法;③滴定法:酸碱、电位和胶体滴定等方法。对壳聚糖脱乙酰度测定方法进行总结与比较,为研究者选择最佳的壳聚糖脱乙酰度测定方法提供理论依据。     

Effects of the molecular weight and the degree of deacetylation of chitosan oligosaccharides on antitumor activity

Effects of the degree of deacetylation (DDA) and the molecular mass of chitosan oligosaccharides (CTS-OS), obtained from the enzymatic hydrolysis of high molecular weight chitosan (HMWC), on antitumor activity was explored. The DDA and molecular weights of CTS-OS were determined by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-TOF MS) analysis. The CTS-OS were found to be a mixture of mainly dimers (18.8%), trimers (24.8%), tetramers (24.9%), pentamers (17.7%), hexamers (7.1%), heptamers (3.3%), and octamers (3.4%). The CTS-OS were further fractionated by gel-filtration chromatography into two major fractions: (1) COS, consisting of glucosamine (GlcN)(n), n = 3-5 with DDA 100%; and (2) HOS, consisting of (GlcN)(5) as the minimum residues and varying number of N-acetylglucosamine (GlcNAc)(n), n = 1-2 with DDA about 87.5% in random order. The cytotoxicities, expressed as the concentration needed for 50% cell death (CC(50)), of CTS-OS, COS, and HOS against PC3 (prostate cancer cell), A549 (lung cancer cell), and HepG2 (hepatoma cell), were determined to be 25 μg·mL(-1), 25 μg·mL(-1), and 50 μg·mL(-1), respectively. The HMWC was approximately 50% less effective than both CTS-OS and COS. These results demonstrate that the molecular weight and DDA of chitosan oligosaccharides are important factors for suppressing cancer cell growth.     

The effect of reaction time and temperature during heterogenous alkali deacetylation on degree of deacetylation and molecular weight of resulting chitosan

The objective of the study is to elucidate the effect of reaction time and temperature during heterogenous alkali reaction on degree of deacetylation (DD) and molecular weight (MW) of the resulting chitosans, and to establish the reaction conditions to obtain desired DD and MW chitosan products. Chitin was extracted from red shrimp process waste. DDs and MWs were determined by infrared spectroscopy (IR) and static light scattering, respectively. The results are as follow: The DD and MW of chitin obtained were 31.9% and 5637 kDa, respectively. The DD of the resulting chitosan increased along with reaction time and/or reaction temperature. The DDs of the resulting chitosan that were obtained from 140°C were higher than those reacted at 99°C. The highest DD of the resulting chitosans after alkali deacetylation at 99 and 140°C were 92.2 and 95.1%, respectively. The DDs of chitosans increased fast at the beginning of reaction process then slowed over time. The reaction rate and rate constant of the deacetylation reaction decreased with increasing DD of the reactant. The MWs of chitosans decreased along with the deacetylation time. MW of those chitosans reacted at 140°C are smaller than those at 99°C. The rate of chitosan degradation was above 43.6%/h in the initial stage, then decreased to about 20%/h. The degradation rate constants raised substantially in the late stage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2917–2923, 2003     

Influence of degree of deacetylation on critical concentration of chitosan/dichloroacetic acid liquid‐crystalline solution

We prepared chitosans with various degrees of deacetylation (DDAs) by mixing completely deacetylated chitosan and acetic anhydride at room temperature without serious degradation and O‐substitution. We obtained a standard curve to measure DDA by plotting the IR absorbance ratio of A₁₅₆₀/A₂₈₈₀ against the known DDAs (from 1–100%) of 10 specimens. The effect of DDA on the critical concentration (C*) of chitosan/dichloroacetic acid solutions required to form mesophase was investigated by optical methods. A maximum C* value of 23 wt % appeared at a relative medium DDA (～20%). The effect was explained by the disordering of chains with medium composition ratios of the copolymer of glucosamine and N‐acetyl glucosamine. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1204–1208, 2002     

常压和加压浸渍法制备壳聚糖性能对比

研究了常压和加压条件下碱液浓度和反应时间对壳聚糖性能的影响。与传统工艺相比,在不改变壳聚糖化学结构、晶型结构的条件下,压力浸渍法反应时间由6 h降到1 h,耗碱量降低了65%。结果表明,压力浸渍法可得到更高脱乙酰度和更高分子量的壳聚糖产品。     

Investigation of different natural sources of chitin: influence of the source and deacetylation process on the physicochemical characteristics of chitosan

Several sea sources for chitin have been investigated, and the chitin content and crystallographic polymorph of the extracted chitin determined. Deacetylation of the chitin was carried out and the physicochemical characteristics of the resulting chitosan studied. The influence of the reaction parameters (reaction duration, temperature, nature of alkaline reagent, etc) was followed. Thus it became possible to determine adequate reaction conditions for obtaining chitosans with the required properties. The physicochemical characteristics of the obtained chitosan are closely related to the taxonomy of the source. New sea sources for chitin have been investigated and considered for industrial purposes. © 2000 Society of Chemical Industry     

紫外分光光度法测定鞣花酸含量的研究

研究了用紫外分光光度法测定鞣花酸含量的一种新方法。其技术关键是将鞣花酸试样溶于适量稀碱配制分析试液,从而解决了鞣花酸不溶于水和难溶于多数有机溶剂的难题。确定了鞣花酸的紫外特征吸收峰的测定波长为 357 nm;验证了新方法在测定条件下试液浓度与吸光度之间的线性关系,并测算了测量误差;进行了新方法测定值的稳定性试验。研究结果表明,该方法具有操作较为简便、耗用溶剂少、分析成本较低、测定结果误差小等特点,适用于鞣花酸工业生产质量监控的产品含量分析。