糠醛的检出及测定

<正> 糠醛与苯胺反应:生成亮红色的化合物,根据这一特征反应便可以检出糠醛。通过实验表明,在紫外光区内,糠醛对一定波长的紫外光选择吸收,且其吸光度与糠醛的浓度成正比,因此可进行定量测定。该方法测定样品时,不必加入任何显色剂和其它试剂进行处理,可直接进行测定。同时,我们应用微型计算机对数据     

紫外光谱定量测定木质纤维预水解液中溶解性木素和糠醛含量

采用紫外光谱探讨了低分子有机酸、糠醛和木质纤维高温预水解液(PHL)的紫外吸收谱图特征。甲酸和乙酸在近205 nm处有显著吸收, 而糠醛在近280 nm处有显著吸收, 以205 nm或280 nm为木素特征吸收位置的传统木素测定方法不适于高温预水解液的溶解性木素测定。研究提出碱性硼氢化钠还原处理预水解液, 消除糠醛的紫外吸收, 进而定量测定溶解性木素含量的方法。结果表明, 硼氢化钠可显著降低近280 nm处吸收值, 预水解条件越高, 还原前后吸收差值降低越多, 说明糠醛类物质含量高。以提取相思木和芦苇木素为标样, 280 nm处吸光度与浓度线性相关系数均达到0.999, 满足定量测定的需要。充分还原前后280 nm吸收差值可用于糠醛的定量, 糠醛标样280 nm处吸光度与浓度线性相关性为0.998, 糠醛测定回收率为98.14%~99.88%, 相对标准偏差为0.17%~0.35%。     

促进剂DOBS纯度测定

本方法是应用紫外分光光度法测定促进剂NOBS的纯度。该促进剂分子中含有可在紫外光区产生吸收的生色基团 ,产生其特征谱线 ,通过测定 2 74nm波长下NOBS的吸光度 ,再参照DM含量对其进行定量分析。     

紫外-可见分光光度法测定吡拉西坦注射液半成品含量

建立测定吡拉西坦注射液半成品含量的紫外分光光度检测方法,为生产车间提供快速的中间体含量检测方法,提高生产效率。用紫外分光光度计对吡拉西坦标准溶液进行波长扫描,确定最适吸收波长,在最适吸收波长下建立吡拉西坦标准品的吸光度-浓度曲线。根据标准曲线测定吡拉西坦样品中吡拉西坦的含量。吡拉西坦的最适吸收波长为220 nm,吸光度-浓度回归方程为:Y=0.1056X+0.2202,R2=0.9999。紫外分光光度法测定吡拉西坦注射液半成品中吡拉西坦含量操作简便、快捷、准确。     

十七烯基咪唑啉的紫外光谱法定量测定研究

基于十七烯基咪唑啉的紫外光谱吸收特性的研究,建立了一种能快速、准确测定十七烯基咪唑啉含量的紫外光谱分析方法。将十七烯基咪唑啉溶解在无水乙醇溶液中,在235 nm处进行紫外光谱测定。操作简单,重现性好,相对标准偏差小于3%;在样品溶液中加入不同浓度的十七烯基咪唑啉标准溶液,回收率在97.6%~102.3%。线性范围为0.005~0.03 mg/mL,相关系数R2为0.999 8。     

紫外分光度法在5-羟甲基糠醛含量测定中影响因素的研究

紫外光谱在测定5-羟甲基糠醛含量时存在一定的误差,笔者对催化反应的溶剂、催化剂和原料等因素的影响进行了探索。实验结果表明,5-HMF标样在284 nm波长下具有非常好的线性关系;反应溶剂离子液体[EMIM]Cl和[BMIM]Cl与二甲基亚枫(DSMO)在特征吸收峰附近几乎没有吸收,而正丁醇有微量吸收;反应催化剂CrCl3、AlCl3、ZnCl2几乎没有吸收,FeCl3、硅钨酸、铬酸钾和磷钼酸有一定吸收(FeCl3>硅钨酸>铬酸钾>磷钼酸);反应原料果糖和葡萄糖在特征吸收峰几乎没有吸收;二甲基亚枫(DSMO)和CrCl3的混合液体对紫外光谱的吸收存在叠加效应。因此,紫外光谱测定5-HMF含量存在一定的误差根本原因是由于分析检测液中其他物质在其特征吸收峰附近有一定的吸收所致。可以采用复配参比液和降低其他物质的浓度等措施降低干扰,提高测量的准确度。     

快速紫外光谱法对阿司匹林有效成分含量的测定

目的 建立一种紫外分光光度法对阿司匹林中有效成分乙酰水杨酸含量进行快速定量分析测定的方法。方法 在固定的波长范围内对标准溶液进行紫外光谱扫描,采集数据确定体系最佳吸光度,于最佳试验条件下绘制标准曲线并进行样品测定。结果 乙酰水杨酸在5.0～100.0μg·mL^-1的浓度范围内呈良好线性关系,r=0.9998,3个加标浓度的相对标准偏差范围为1.16%～4.87%,样品回收率范围为97.15%～99.90%。结论该法操作简便、分析快速、试剂便宜、方法稳定,适用于批量阿司匹林片剂中乙酰水杨酸含量的快速定量测定。     

波谱分析教学中紫外光谱部分的教学设计

波谱分析课程是化学化工类本科生及研究生的必修课,涉及到有机化合物结构表征的方法(紫外光谱、红外光谱、核磁共振波谱、质谱),其中各种测试方法的基本理论及应用不同.紫外光谱针对共轭有机化合物,对其紫外吸收的波长及强度进行表征.在紫外光谱这章的教学中,为了提高教学效果,除了加强基础知识及基本理论外,各类有机化合物的紫外吸收的...     

紫外区酸碱双吸收体系双波长分光光度法测定苯基J酸中双J酸

本文提出了一种新的紫外区分光光度法—酸碱双吸收体系双波长分光光度法。利用具有氨基、羟基的芳香族化合物在酸性和碱性水溶液中紫外光谱的显著差异,波长对的组合放在两个完全独立的吸收体系中进行,使该方法扩大了波长对选择范围。结合苯基J酸中双J酸测定实例对原理、测定条件进行探讨。     

应用紫外法测定乙肝疫苗生产中蔗糖离心样品蛋白浓度

血源乙肝疫苗生产过程中，蔗糖速率区带离心后样品（以下简称离心样品）须测定蛋白浓度。目前，用Lowry法测定，不仅操作繁琐、费时、费试剂，而且由于样品中蔗糖干扰而明显影响结果的准确性。本文应用紫外法代替Lowry法，操作简便、快速，结果准确可靠。首先，经实验证明，蔗糖对280nm紫外光无吸收。在此基础上建立蛋白浓度和紫外吸收值之间的线性方程（以下简称C－A方程）。随机抽取乙肝疫苗生产中14批离心样品，透析去糖后用Lowry法测定蛋白浓度。与此同时测定280nm的吸收值。以蛋白浓度为纵坐标，以紫外吸收值为横坐标，进行一无线性…     

醋酸水解玉米芯中木聚糖的动力学

利用醋酸作为催化剂水解玉米芯中半纤维素来制备还原糖,测定了温度在160-200℃、固液质量比为1∶15、搅拌速度为500 r/min下,不同水解时间水解液中还原糖的收率以及副产物糠醛的收率.利用半纤维素高温液态水的Garrote模型拟合还原糖生成过程.实验表明,该模型能够较好地描述还原糖生成过程以及副产物糠醛的产生过程...     

Green Liquor Pretreatment of Mixed Hardwood for Ethanol Production in a Repurposed Kraft Pulp Mill

Abstract

The development of a new, relatively simple process, which uses green liquor (sodium carbonate and sodium sulfide) as a pretreatment for the production of ethanol is described in this article. The pulps produced by this process can be enzymatically hydrolyzed to monomeric sugars with a high overall sugar recovery. The use of green liquor for pretreatment ensures that the chemicals used during pretreatment can be recovered efficiently using proven technology and can be easily implemented in a repurposed kraft pulp mill. The yield of pulps produced by the green liquor pretreatment process is about 80% with nearly 100% cellulose and 75% xylan in retention in mixed southern hardwood. The low pH prevents the random hydrolysis of polysaccharide and secondary peeling reactions from occurring during the pretreatment, resulting in higher retention of the polysaccharides in pulp. About 35% of the lignin is removed during the green liquor pretreatment process, which is sufficient for efficient enzymatic hydrolysis. The amount of sugar produced in enzymatic hydrolysis increased with both the green liquor and enzyme charge. The increase in enzymatic hydrolysis efficiency was small as the total titrateable alkali was increased beyond 12–16%. With green liquor pretreatment at 16% Total Titrateable Alkali (TTA), the overall sugar recovery for hardwood was shown to be around 77% at a cellulase charge of 20 FPU/gm of substrate. A sugar recovery of 80% could be achieved at higher enzyme charges. These levels of sugar recovery are competitive with other pretreatments for hardwood. This novel pretreatment process can be used to repurpose kraft mills, which are being closed due to a decrease in the demand for paper in North America, for production of ethanol.     

MCP中糖醛酸的含量测定

采用间羟基联苯法对MCP中的半乳糖醛酸进行含量测定,研究了四硼酸钠/硫酸溶液用量,加酸后沸水浴时间和间羟基联苯溶液用量和中性糖对测定结果的影响。试验表明该方法可排除中性糖对测定结果的干扰,简便易行,专一性强。     

Improvement of Furfural Production from Concentrated PreHydrolysis Liquor (PHL) of a Kraft-Based Hardwood Dissolving Pulp Production Process

Hemicelluloses present in the prehydrolysis liquor (PHL) of the hardwood kraft-based dissolving pulp production process can be utilized in the production of furfural, which is an important renewable, non-petroleum-based platform chemical. A lower furfural yield was observed from the concentrated sugars in PHL in acetic-acid-catalyzed systems. The reaction rate of sugar consumption and furfural destruction in PHL was higher than those of model xylan and xylose systems, which may be due to the side-reactions of lignin with sugars and carbonization of oligomeric sugars. In order to minimize these side-reactions, a steam-stripping method of generated furfural was adopted. The results showed that the method was effective in increasing the furfural yield (41.5%) from the concentrated PHL.     

Comparisons of existing pretreatment,saccharification, and fermentation processes for butanol production from agricultural residues

Some of the most recent, relevant, industrial and academic contributions made in the field of butanol production are reviewed here. The focus on butanol is due to the growing demand for non‐fossil biofuels. In addition, butanol can be mixed with fossil fuels or can be used alone, allowing an alternative to gasoline. Butanol can be synthesised biologically using sugars extracted from biomass such as agricultural waste. This agricultural waste must be pretreated before it is suitable for sugar extraction. Following this stage, enzymatic hydrolysis is employed, before performing fermentation using microorganisms. This article summarises some of the economical methods such as simultaneous saccharification and fermentation (SSF). Different pretreatment and saccharification processes were compared. Acid pretreatment and saccharification achieved the highest sugar concentrations from wheat straw. Monoethanolamine pretreatment achieved highest sugars from hardwood. Comparisons and analysis of different types of fermentation processes illustrated that immobilised reactor provided the best butanol rate of production. Integration of fermentation with product removal process improved butanol production in immobilised reactor. Gas stripping method was illustrated to be the product removal process. © 2011 Canadian Society for Chemical Engineering     

Preliminary Results on an Approach for the Quantification of Lignin-Carbohydrate Complexes (LCC) in Hardwood Pulps

Abstract

The literature on biomass research contains many references to lignin-carbohydrate complexes (LCC) decreasing the rate of delignification in chemical pulp production, decreasing the yield of cellulosic ethanol via fermentation, and decreasing forage digestibility. However, it is difficult to find correlations between rates of the processes above and initial LCC concentration. One of the main reasons for the lack of such correlations is the absence of methods for accurate quantification of LCC. In this investigation, repeatable and reproducible determinations of bound sugars at monomeric concentrations as low as 0.3 wt% on enzymatic lignin (EL) have been achieved. The bound sugars are hydrolyzed by H₂SO₄, most likely as low molecular weight oligomers. In the same H₂SO₄ treatment, the oligomers are hydrolyzed to monomers which are subsequently quantified by ¹H NMR analyses. A significant enrichment of bound arabinan was previously reported when a crude milled wood lignin (MWL) was compared to the starting wood meal. A similar arabinan enrichment was observed for ELs from kraft and soda-AQ (SAQ) pulps in the present study. Also, well-resolved cross-peaks have been obtained in 2D HSQC NMR analyses of ELs. It has so far been confirmed that the EL from a 30.6 kappa number SAQ pulp from sugar maple contained ～30% more benzyl ethers linked to primary-OH groups in sugar units than the corresponding EL from a 33.7 kappa number kraft pulp.     

Production of fermentable sugars from corn fiber using soaking in aqueous ammonia (SAA) pretreatment and fermentation to succinic acid using <Emphasis Type="Italic">Escherichia coli</Emphasis> AFP184

Conversion of corn fiber (CF), a by-product from the corn-to-ethanol conversion process, into fermentable sugar and succinic acid was investigated using soaking in aqueous ammonia (SAA) pretreatment followed by biological conversions, including enzymatic hydrolysis and fermentation using genetically engineered E. coli (AFP184). The SAA pretreatment (using a 15% w/w NH₄OH solution at a solid-to-liquid ratio of 1: 10 at 60 °C for 24 h) removed 20-38% of lignin and significantly improved the digestibility of the treated solid (85-99% of glucan digestibility). Following the enzymatic hydrolysis, the sugar-rich hydrolysate was subjected to dilute sulfuric acid treatment (1 wt% sulfuric acid and 120 °C for 1 h), which hydrolyzed the oligosaccharides in the hydrolysate into fermentable monomeric sugars. The mixed sugar hydrolysates containing hexose and pentose obtained from the two-step hydrolysis and SAA pretreatment were fermented to succinic acid using a genetically engineered microorganism, Escherichia coli AFP184, for evaluating the fermentability. Engineered E. coli AFP184 effectively converted soluble sugars in the hydrolysate to succinic acid (20.7 g/L), and the production rate and yield were further enhanced with additional nutrients; the highest concentration of succinic acid was 26.3 g/L for 48 h of fermentation.     

Residual Sugars in Klason Lignin

The Klason method–dissolution of carbohydrates in sulfuric acid–has been widely used for the determination of lignin content in woody materials. It was an unsolved problem, however, whether Klason lignin still contains carbohydrates. We observed previously that Klason lignin becomes almost completely soluble in water after ozone treatment. In this work, the residual sugar content of Klason lignin was determined on the basis of the above observation.

Water-soluble lignin was prepared by ozone treatment (25 and 45 min) of finely-crushed Klason lignin obtained from spruce and birch wood meals. After hydrolysis with 2N-trifluoroacetic acid followed by sodium borohydride reduction, residual sugars were determined by GLC as their alditol acetates.

Klason lignin ozonated for 25 min contained 0.75% and 0.95% neutral sugars for spruce and birch, respectively. Most of the residual sugars were derived from hemicelluloses. Because ozone degrades carbohydrates, the prolonged ozonation was found to decrease the content of residual sugars. Therefore, the values obtained here are the minimum ones for the residual sugar content in Klason lignin.     

Enzymatic Hydrolysis of Corn Stover after Pretreatment with Dilute Sulfuric Acid

Although many previous studies have been carried on the enzymatic hydrolysis of corn stover after pretreatment with dilute sulfuric acid, this paper emphasizes the use of different conditions to attain the highest yields of two sugars, xylose and glucose, from both stages. The pretreatment was performed at a range of sulfuric acid concentrations of 2, 4 and 6 % at 80, 100 and 120 °C. Up to 77 % xylose yield was obtained while the glucose yield was only 8.4 %. The corresponding solid phase was hydrolyzed by cellulase and the influences of five factors and their interactions on enzyme hydrolysis were evaluated by response surface methodology based on one‐factor‐at‐a‐time experiments. The optimal levels for each variable to obtain the highest reducing sugar yield were as follows: enzyme concentration of 22 FPU/g substrate, substrate concentration of 77 g/L, temperature of 49 °C, pH 4.8 and reaction time of 38 h. A reducing sugar yield of 42.11 g/100 g substrate was achieved, which was consistent with the predicted value of 42.13 g/100 g substrate. Compared with the one‐factor‐at‐a‐time experiments, there was a 9.4 % increase in reducing sugar yield when the enzyme concentration was decreased to 3 FPU/g substrate, the substrate concentration increased to 17 g/L and the reaction time dropped to 22 h. The total sugar released from the two stages was 62.81 g/100 g substrate.     

UPLC-ELSD法测定烟草中的水溶性糖

采用Waters公司的ACQUITY UPLC BEH Amide色谱柱,建立烟草中水溶性糖的超高效液相-蒸发光散射(UPLC-ELSD)检测方法。果糖、葡萄糖、蔗糖和麦芽糖4种水溶性糖在6.5 min之内分离完全,线性相关系数(R2)果糖:0.999 5,葡萄糖:0.999 8,蔗糖:0.999 9,麦芽糖:0.997 4,回收率依次分别为106.5%,102.4%,91.2%,100.1%,表明方法可用于烟草中水溶性糖的稳定、快速、准确分析。