Spectrophotometric Determination of Water-Soluble Hexavalent Chromium and Determination of Total Hexavalent Chromium Content of Portland Cement in the Presence of Iron (III) and Titanium (IV) Using Derivative Ratio Spectrophotometry

A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement with 1, 2, 5, 8 Tetrahydroxyanthraquinone, (Quinalizarin, QINZ) at pH 1.5. The European Directive (2003/53/EC) limits the use of cements so that it contains no more than 2 mg.Kg-1 of water-soluble Cr (VI). The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement. The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances). The validity of the method is thoroughly examined and the proposed method gives satisfactory results. A derivative spectrophotometric method has been developed for the determination of total Cr (VI) in Portland cement in the presence of Fe (III) and Ti (IV). The hexavalent chromium complex formed at pH 1.5 allows precise and accurate determination of chromium (VI) over the concentration range 0.05 to 3.0 mg.L-1of chromium (VI). The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The MDL (at 95% confidence level) was found to be 25 ng/mL for chromium (VI) in National Institute of Standards and Technology (NIST) cement samples using the proposed method.

The thermal and storage stability of bovine haemoglobin by ultraviolet-visible and circular dichroism spectroscopies

The effects of temperature,pH and long-term storage on the secondary structure and conformation changes of bovine haemoglobin（bHb） were studied using circular dichroism（CD） and ultraviolet-visible（UV-vis） spectroscopies.Neural network software was used to deconvolute the CD data to obtain the fractional content of the five secondary structures.The storage stability of bHb solutions in pH 6,7 and8 buffers was significantly higher at 4 ℃ than at 23 ℃ for the first 3 days.A complete denaturation of bHb was observed after 40 days irrespective of storage temperature or pH.The bHb solutions were also exposed to heating and cooling cycles between 25 and 65 ℃ and structural changes were followed by UVvis and CD spectroscopies.These experiments demonstrated that α-helix content of bHb decreased steadily with the increasing temperature above 35 ℃ at all pH values.The loss in a-helicity and gain in random coil conformations was pH-dependent and the greatest under alkaline conditions.Furthermore,there was minimal recovery of the secondary structure content upon cooling to 25 ℃.The use of bHb as a model drug is very common and this study elucidates the significance of storage and processing conditions on its stability.

A Comparative Analysis of Caffeine Extraction Efficiency from Different Tea Varieties and Its Effect on Human Physiology: A Spectrophotometric Investigation

The current work imitates the trivial method which intricates the abstraction along with classification of caffeine accessible in variability of decoction shrubberies which are expended in two different states of India (Telengana & Uttar Pradesh). As per observation individuals of both the states are identical tender of consumption of tea. Abstraction progression tangled variability of stages which are discoursed in the work. In addition, the outcome of drinking of caffeine or the permitted ingestion of caffeine over tea has also been conferred through the work and linked the data with the literature data. In this study, we used a UV-visible spectrophotometer as well as liquid-liquid extraction method to determine the caffeine content in various tea samples. The significance of this study lies in the fact that accurate determination of caffeine content is essential for quality control and labeling of tea products. The UV-visible spectrophotometer method was found to be simple, reliable, and sensitive for the detection of caffeine in tea samples.

Rapid accuracy determining DNA purity and concentration in heavy oils by spectrophotometry methods

DNA analysis is the core of biotechnology applied in petroleum resources and engineering. Traditionally accurate determination of DNA purity and concentration by spectrometer is the first and critical step for downstream molecular biology research. In this study, three different spectrophotometry methods, BPM, NDTT and NPMTTZ were compared for their performance in determining DNA concentration and purity in 32 oil samples, and molecule methods like quantitative real-time PCR (qPCR) and high-throughput sequence were also performed to help assess the accuracy of the three methods in determining DNA concentration and purity. For ordinary heavy oil (OHO), extra heavy oil (EHO) and super heavy oil (SHO), the characteristics of high viscosity (η), density (ρ) and resin plus asphaltene content will affect the DNA extraction and UV determination. The DNA concentration was decreased as density increased: OHO (11.46 ± 18.34 ng/μL), EHO (6.68 ± 9.67 ng/μL) and SHO (6.20 ± 7.83 ng/μL), and the DNA purity was on the reverse: OHO (1.31 ± 0.27), EHO (1.54 ± 0.20), and SHO (1.83 ± 0.32). The results suggest that spectrophotometry such as BPM and NPMTTZ are qualitatively favorite methods as the quick non-consumable methods in determining DNA concentration and purity of medium oil and heavy oil.

Determination of Total Lignanoids in Tangjiangshenkang Granules by Two-Wavelength Ultraviolet Spectrophotometry

[Objectives] To establish a determination method for the content of total lignanoids in Tangjiangshenkang granules. [Methods] Two-wavelength ultraviolet spectrophotometry (TWBS) was used to scan arctiin control solution, chlorogenic acid control solution and Tangjiangshenkang granule test solution in the range of 200-400 nm. In the ultraviolet scanning diagram of arctiin reference solution, the maximum absorption wavelength of 280 nm was determined as the determination wavelength λ 1, the detection wavelength in the ultraviolet scanning diagram of chlorogenic acid reference solution ( λ 1=280 nm) was determined, and 350 nm was the reference wavelength λ 2;the content of total lignosides in Tangjiangshenkang granules was determined with arctiin as the reference substance. [Results] The precision, accuracy, and durability of this method were fine. The concentration of arctiin was linearly correlated with the absorbance difference in the range of 0.007 95-0.071 55 mg/mL ( r =0. 999 9). The average recovery of arctiin was 100.8%, and the RSD value was 1.04% ( n =6). Calculated as arctiin, three batches of Tangjiangshenkang granules contain no less than 20% of total lignosides. [Conclusions] The method has the advantages of simple operation, good accuracy, precision and reliable stability. It can be used as the content determination and quality control method of total lignosides in Tangjiangshenkang granules.

亚甲蓝分光光度法测定水中阴离子表面活性剂含量的方法改进

对亚甲蓝分光光度法(GB 7494—1987)测定水中阴离子表面活性剂含量进行了方法改进。以毒性相对较小的二氯甲烷取代三氯甲烷作为萃取剂,试管取代分液漏斗,利用振荡器进行萃取。结果表明:改进方法的最佳萃取时间为1.5 min,单个样品的分析时间在10 min以内;十二烷基苯磺酸钠标准曲线的线性范围在2.0 mg·L^(-1)以内,检出限(3s/k)为0.0297 mg·L^(-1);对十二烷基苯磺酸钠标准溶液重复测定6次,测定值的相对标准偏差(n=6)均小于9.0%;对空白样品进行加标回收试验,回收率为95.0%~99.1%。

水基炭黑-胶原蛋白纳米流体制备及稳定性实验

纳米流体由于其优异的光热转换性能,已成为新型太阳能集热介质的研究重点;但因其稳定性差、制备工艺复杂,未能在实际应用中得到推广。本文以去离子水为基液,通过两步法制备炭黑-胶原蛋白纳米流体。探究了材料添加顺序、胶原蛋白种类、超声时间、材料配比以及溶液pH等对纳米流体稳定性的影响。结果表明,制备水基炭黑-胶原蛋白纳米流体时,先分散炭黑再加入胶原蛋白可以提高其稳定性;猪皮胶原蛋白更适用于炭黑-胶原蛋白纳米流体的制备;超声45min,炭黑胶原蛋白质量配比为1/20,悬浮液pH在6.5~7.5之间制备得到的纳米流体稳定性较好。本研究有助于今后水基炭黑-胶原蛋白纳米流体产业化应用于太阳能光热转换领域。

双波长光度法测定热处理橡胶木中支链淀粉和直链淀粉的含量

橡胶木中直链淀粉和支链淀粉的组成比例直接影响淀粉的化学特性,橡胶木热处理过程中,淀粉发生不同程度热降解影响其比例发生变化,分析其含量变化将为热处理橡胶木热解机制研究提供理论基础.研究采用单因素法优化了提取方法参数,并建立了双波长光度法检测橡胶木中直链淀粉和支链淀粉含量的定量分析方法,检验了该分析方法的精密度、稳定性和加标回收率.结果表明,直链淀粉和支链淀粉的标准曲线方程分别为y=0.02499x-0.1136和y=0.00159x-0.0005,其回归系数R^(2)均为0.998,方法前处理样品简便、快速,分析方法稳定性好、灵敏度高,回收率稳定,适用于橡胶木中直链淀粉和支链淀粉含量的定量分析.分析比较了橡胶木素材及不同温度(125、155、185℃)热处理橡胶木中直链淀粉和支链淀粉的含量,橡胶木素材中支链淀粉含量远高于直链淀粉,质量比约为8∶1.随着热处理温度升高至155℃,直链淀粉含量出现明显下降,而温度升高至185℃,支链淀粉含量出现明显下降趋势.

连续流动-钼酸铵分光光度法测定土壤全磷

利用硫酸-高氯酸湿法消解土壤,采用连续流动分析仪直接测定消解液磷酸根含量,建立了高通量测定土壤全磷的实验方法。方法检测限6.0 mg·kg^(-1),土壤样品的加标回收率为85%~100%。将该方法用于土壤标准物质(GBW07405、GBW07406a)全磷含量测定,结果准确,相对标准偏差(RSD)分别为3.5%、4.5%(n=3)。方法具备无需调节待测液pH值、分析速度快、消耗试剂少、结果准确可靠等优点,适用于大批量土壤全磷的测定分析。

加速老化的无铬鞣革中游离苯胺的FIA-UV法分析

采用流动注射分析-紫外光谱法(FIA-UV),基于苯胺与亚硝酸盐在酸性条件下发生的重氮化反应及其在碱性条件下的偶合显色反应,实现苯胺的有效检测.通过实验参数的优化,确定495 nm为最大吸收波长,建立了苯胺质量浓度在0.002~2.0 mg/L范围内与峰高具有良好线性关系的模型(R^(2)=0.9997),检出限为1.62μg/L,重复性(RSD)为0.71%.该方法在加速老化后皮革萃取液中的应用表现出97.8%~103.8%的加标回收率,相较国标法具有更优的抗干扰能力和更高的检测精度.成功建立的苯胺检测新方法,为无铬鞣革产品的质量控制及环境监测提供了重要的技术支持,有助于提高公共健康和环境保护水平.

乙酰丙酮分光光度法在室内甲醛检测中的应用

目的:为有效利用乙酰丙酮分光光度法,对室内甲醛含量进行检测。方法:通过控制样品采集、实验检测过程,验证乙酰丙酮分光光度法检测室内甲醛含量的回收率和精密度,并对6户住宅装修后的室内甲醛浓度进行检测。结果:吸光度和甲醛含量的线性回归方程为Y=0.00468X+0.000413,R^(2)=0.9998。乙酰丙酮分光光度法检测的3组5μg/mL甲醛标准溶液回收率范围为87.46%~97.28%,相对标准偏差(RSD)分别为:1.25%、0.90%、0.64%,都小于1.5%,重复性较好;6户住宅装修后的甲醛质量浓度满足国家标准,均小于0.08 mg/m^(3)。结论:乙酰丙酮分光光度法对于检测室内甲醛钠的结果良好可靠。

紫外分光光度法测定歧化松香中去氢枞酸含量的 干扰因素研究

利用液相色谱仪、制备液相色谱仪、气相色谱质谱联用仪,对歧化松香(DR)中去氢枞酸(DA)紫外光谱测定方法的干扰因素进行了详细研究。测定的市售不同省份的5个样品中有2个主要干扰物质,进一步定性,确定干扰物质1为6,8,11,13-枞四烯酸(ATA),干扰物质2为混合物,主要检出物为去氢枞醛(D)和枞酸(AA)。采用二阶导数光谱法和偏最小二乘(PLS)法对紫外光谱数据进行分析,以消除去氢枞酸紫外分光光度法的干扰,结果表明:PLS法比二阶导数光谱法误差更小,能够同时消除多种干扰因素,使测试结果更加接近真实值。

沉积岩中黄铁矿含量及其硫同位素组成连续测定方法研究

沉积岩中黄铁矿的含量和硫同位素组成研究可以用于判断沉积环境特征,反演成岩成矿过程。设计了一套多通道的黄铁矿硫提取装置,确定了装置的加热温度为130℃,实验时间为2h,优化了实验流程,实现一次提取同时满足黄铁矿含量及其同位素组成测定需要。采用亚甲基蓝分光光度法测定硫含量和元素分析仪-气体同位素质谱法测定黄铁矿硫同位素组成。亚甲基蓝分光光度法的标准曲线的线性相关性R^(2)=0.9999,黄铁矿样品的加标回收率介于94%~100%之间,10次测量的相对标准偏差为1.9%。黄铁矿经过铬还原法提取生成的硫化银的硫同位素组成的测试结果和本身的测试结果在误差范围内一致,精度≤0.2‰,可以满足沉积岩中黄铁矿硫同位素测试需求。

乙二醇锑中锑含量分析方法比较

介绍了聚酯催化剂乙二醇锑中锑含量分析方法,从分析技术原理、实验设备材料、影响因素、经济适用性等方面进行了对比分析。对比结果表明,3种分析方法适用于不同的分析条件,不同的生产企业和检测单位可以根据自身的需要建立适合自己企业的分析方法。文章的研究内容对聚酯催化剂乙二醇锑中锑含量分析方法的选择具有一定的指导意义,可为相关领域的研究提供一定的参考。

水中总磷的测定及不确定度评定

目的:测量水样中总磷含量并进行评定。方法:采用钼酸铵分光光度法进行测定,通过测量的重复性、标准溶液的配制和标准曲线的拟合等分量对测量中影响水样总磷含量结果的不确定度因素进行评定。结果:水样中总磷质量浓度的扩展不确定度为0.027 mg/L,总磷质量浓度为0.350 mg/L±0.027 mg/L。结论:标准溶液配制引入的不确定度为影响不确定度的主要因素,水样单从总磷质量浓度来看为Ⅳ类水质。

原子吸收光谱法测定苦瓜中微量金属元素的含量

用微波消解法对苦瓜进行预处理,采用火焰原子吸收光谱法测定了苦瓜中钙、镁、铁、锌四种微量金属元素的含量。在最佳条件下测得苦瓜中各金属元素的含量分别为Ca:3843.50μg/g,Mg:2545.492μg/g,Fe:93.3415μg/g,Zn:77.685μg/g;RSD为0.19%~0.85%;检出限为0.0020μg·mL^(-1)~0.0703μg·mL^(-1);相关系数为0.9927~0.9997;加标回收率为94.60%~102.92%,此方法简单、快捷、经济、有效。

壳聚糖-魔芋葡甘聚糖复合絮凝剂在印染污水处理中的应用

利用改性-交联的方法制备壳聚糖/魔芋葡甘聚糖复合絮凝剂,以亚甲基蓝为例,对印染废水进行处理。探究了壳聚糖/魔芋葡甘聚糖复合絮凝剂的用量、吸附时间以及pH值对印染污水吸附率的影响。结果表明:在常温条件下,亚甲基蓝溶液初始浓度为8.0 mg/L,溶液PH为9,壳聚糖/魔芋葡甘聚糖复合絮凝剂的投加量为0.3 g,吸附时间72 h,亚甲基蓝溶液吸附率达到98.90%。

基于碳点变色性能的紫外-可见分光光度法测定脱硫液和废水中硫离子的含量

以柠檬酸为碳源,尿素为氮源,采用水热法合成了具有变色性能的碳点(CDs),利用该CDs与S^(2-)的褪色反应,提出了紫外-可见分光光度法(UV-Vis)测定脱硫液和废水中S^(2-)含量的方法。通过循环预处理系统分离样品中的S^(2-),分取0.5 mL待测样品溶液和4.5 mL 100 mg·L^(-1)CDs溶液,混匀,将酸度调节至pH 8,于30℃反应15 min,快速冷却至室温,采用UV-Vis测定反应前后体系在610 nm处的吸光度。结果表明,该CDs变色是氧化导致的。在pH 8条件下,S^(2-)使CDs发生选择性褪色反应;S^(2-)的质量浓度在0.05~1.00 mg·L^(-1)和1.00~15.00 mg·L^(-1)内与对应的吸光度差值呈线性关系,检出限(3S/N)为0.043 mg·L^(-1)和0.073 mg·L^(-1);对实际样品进行加标回收试验,回收率为98.0%~106%,测定值的相对标准偏差(n=6)为0.92%~1.1%。方法用于实际脱硫液和废水样品分析,并与国家标准GB/T 16489-1996进行比对,结果显示两种方法的测定结果无显著性差异。

玉米须总黄酮含量检测络合显色体系的比较

采用紫外可见分光光度法建立最适合玉米须总黄酮(Corn Silk Total Flavonoids,CSTF)含量检测的络合显色体系。实验选用体积分数60%乙醇为溶剂对CSTF进行提取,并以不同极性溶剂对CSTF进行分级萃取,最终获得正己烷(Normal Hexane,n-Hexane)、乙酸乙酯(Ethyl Acetate Extracts,EAE)和正丁醇(Bormal Butanol,n-BuOH)萃取物。以玉米须中不同类型黄酮为对照品,比较研究NaNO_(2)-Al(NO3)3/AlCl3-NaOH和KAc-Al(NO3)3/AlCl3四种络合显色体系下乙酸乙酯和正丁醇萃取物中总黄酮含量。同时采用高效液相色谱(High Performance Liquid Chromatography,HPLC)对乙酸乙酯和正丁醇萃取物中黄酮含量进行测定,从而确定最适合的对照品种类和显色体系。结果表明,HPLC法检测乙酸乙酯和正丁醇中黄酮含量分别为83.45%和57.36%,经比较研究发现,与HPLC法检测总黄酮含量最接近的是以芦丁为标准品的KAc-Al(NO3)3络合显色体系。综上所述,KAc-Al(NO3)3络合显色体系是玉米须和各萃取物总黄酮含量检测的最佳方法,该方法检测CSTF提取液黄酮含量为1.08%。该方法操作简便、准确度高,可为玉米须黄酮类物质的开发利用和质量管控提供依据。

希托夫法测定离子迁移数的影响因素探究

离子迁移数作为物理化学课程中电化学部分的一个重要概念,其测定实验被设置在多所高校的物理化学实验课程中。文献调研及过往教学实践表明,使用希托夫(Hittorf)法测定的离子迁移数,结果与文献值有较大出入。为了降低测定误差,以及探究测试结果的影响因素,本实验从溶液装液量控制、断液断电顺序、计算电量的数据来源三个方面进行改进,尽可能降低实验操作和浓度测定导致的误差,从而分析真正影响测试结果的因素。实验表明,当采用电流乘以时间作为电量的数据来源,且采用阴极区溶液计算离子迁移数时,所得结果更接近实验参考值。