激光拉曼光谱内标法直接测定甲醇浓度

利用甲醇溶液中的CH3对称伸缩峰(2843 cm-1)的激光拉曼光谱峰,同时以本底溶液水为内标物,组成相对强度,对溶液中的甲醇含量进行了测定研究,建立了激光拉曼光谱直接法测定甲醇含量的方法,其线性范围为5%~40%,线性相关系数为0.9966,检出限为0.29%。并对模拟样品和制备液相色谱待回收废液进行了甲醇浓度的测定,其浓度分别为13.7%、9.41%和58.8%,RSD分别为0.78%、0.75%和1.34%。该方法简单、操作方便,无需添加其它任何化学试剂等优点。     

激光拉曼光谱内标法直接测定甲醇含量

<正>激光拉曼光谱法作为一种新型无损检测技术,广泛应用于样品的定性、定量分析[1-3]。目前,样品中甲醇的定量分析方法常用的有气相色谱法[4]、分光光度法[5]和传感器法[6]等。本工作通过不同浓度的甲醇拉曼光谱特征峰(1 016.46cm-1)与乙醇的拉曼光谱特征峰(877.95cm-1)组成相对强度比,建立线性回归方程。本法具有测定简单、操作方便,无需添加其他化学试剂,可用于甲醇含量的直接检测。     

可待因及福尔可定的密度泛函理论计算模拟和表面增强拉曼光谱测定北大核心CSCD

运用密度泛函理论(DFT)对可待因及福尔可定进行几何构型优化,从而对标准品粉末的拉曼光谱的振动模式进行指认和归属,并与低浓度水平标准溶液的表面增强拉曼谱图进行比较。进一步优化了表面增强拉曼光谱检测条件,并摸索可待因及福尔可定的测定下限及定量分析的可行性。结果表明,可待因及福尔可定大部分特征峰拉曼位移的理论计算值、拉曼光谱测定值、表面增强拉曼光谱测定值是一致的,但会有一定程度的蓝移和红移;可待因、福尔可定的测定下限均为10 mg·L^(-1)。可待因在631.29 cm^(-1)和1 595.26 cm^(-1)处、福尔可定在628.58 cm^(-1)和1 251.41 cm^(-1)处的特征峰强度比值,与其对应的质量浓度(40~100 mg·L^(-1))呈线性关系。对空白基质进行加标回收试验,可待因和福尔可定的回收率分别为99.0%~105%和102%~104%,测定值的相对标准偏差(n=5)分别为5.3%,5.9%。上述方法可为这两种管制药品提供拉曼光谱检测的理论依据和快检支持。     

基于拉曼光谱成像的食品中化学添加剂的无损检测

基于拉曼光谱成像技术对小麦粉中过氧化苯甲酰和L-抗坏血酸进行快速、 无损、 原位检测, 并对2种添加剂的空间分布进行了可视化研究. 采用实验室自行搭建的线扫描式拉曼光谱成像系统, 激发光源波长为785 nm, 有效光谱范围为0~2885.7 cm^-1. 分别在小麦粉中添加含量为0.1%~30%的过氧化苯甲酰和L-抗坏血酸, 对制备的样品进行拉曼光谱扫描, 选取感兴趣区域的光谱信号进行平均, 得到平均光谱代表该样品的拉曼信息. 分别选取过氧化苯甲酰和L-抗坏血酸的2个特征峰, 与该物质在小麦粉中的含量建立线性关系, 其决定系数R²分别为0.9828 和0.9912. 采集的特征波段拉曼图像经过自适应迭代重加权惩罚最小二乘(airPLS)方法扣除荧光背景后, 选取合适的特征峰强度作为阈值, 对校正拉曼图像进行二值化分析, 得到添加物的空间分布可视化图像. 该方法与点检测拉曼技术相比, 具有检测结果准确且检测时间较短的优势, 且可以实现不均匀样品中多种物质的同时检测与分布可视化.     

ICP-AES法测定氮化硼中铁、钙含量

建立微波消解–ICP–AES测定氮化硼中铁、钙含量的方法。采用高压微波消解法对样品进行溶解,考察了硼基体和共存元素对铁、钙测定结果的影响。结果表明,铁、钙标准溶液的质量浓度与光谱强度线性良好,相关系数均大于0.999,铁、钙的检出限分别为0.024,0.006μg/mL,加标回收率分别为96%~103%,99%~100%,测定结果的相对标准偏差分别为2.46%,1.10%(n=7),用该法对BN标准样品进行测定,测定结果在标准值允许范围内。该方法具有快速、准确、灵敏度高等优点,适用于氮化硼中铁、钙含量的检测。     

气相色谱法测定电子烟烟液及气溶胶中双乙酰和乙酰丙酰

建立气相色谱法氢火焰离子化检测器测定电子烟烟液和气溶胶中双乙酰和乙酰丙酰含量的方法。样品以20 mL乙醇为萃取剂,涡旋振荡萃取10 min,采用气相色谱外标法进行定量分析。双乙酰和乙酰丙酰质量浓度在0.5~50 μg/mL范围内与色谱峰面积呈良好的线性关系,相关系数分别为0.999 6、0.999 4,方法检出限分别为0.044、0.052 μg/mL。烟液中双乙酰和乙酰丙酰测定结果的相对标准偏差为2.5%~4.3%(n=6),样品加标回收率为95.0%~102.5%;气溶胶中双乙酰和乙酰丙酰测定结果的相对标准偏差为3.1%~4.6%(n=6),样品加标回收率为92.7%~102.3%。气溶胶中双乙酰和乙酰丙酰理论浓度与实测浓度具有较强的相关性(对于双乙酰r~2=0.990 1,对于乙酰丙酰r~2=0.994 7),说明双乙酰、乙酰丙酰烟液通过雾化直接转移至气溶胶中。该方法准确度高,重现性好,检出限低,可满足电子烟样品的检测需求。     

基于单细胞拉曼光谱技术的葡萄球菌黄素生物合成分析

利用光镊拉曼光谱技术研究吲哚对金葡菌细胞中葡萄球菌黄素合成的抑制作用以及色素含量在分批培养过程中的动态变化。收集经不同浓度吲哚(终浓度为0,0.2,0.6,0.8,1.2和1.5 mmol/L)处理后的以及不同培养时间的金葡菌单细胞的拉曼光谱,以光谱1523 cm-1峰强度表征色素含量,并与紫外可见分光光度法得到的结果进行比较。结果表明,细菌拉曼光谱1523 cm-1峰强度与分光光度法测得的色素含量有良好的线性关系,相关系数达0.9772;群体和单细胞水平的光谱数据均表明,吲哚可剂量依赖性地抑制葡萄球菌黄素的合成,色素含量降低幅度超过70%;在分批培养中细菌色素含量在对数生长中期(12 h)达到最大值,各个时间点的群体内部细胞间色素含量的异质性较小,RSD在39.2%~61.1%之间。本研究表明光镊拉曼光谱技术是一种在单细胞水平分析葡萄球菌黄素含量的可靠方法。     

气相色谱–质谱法测定白酒中的邻苯二甲酸酯类

采用气相色谱–质谱法对常见名贵白酒中的16种邻苯二甲酸酯类含量进行测定。将样品提取、净化后,经气相色谱–质谱联用仪进行分离测定。采用特征选择离子检测扫描(SIM),以色谱保留时间和色谱碎片的丰度比定性,以峰面积外标法定量。16种邻苯二甲酸酯类物质的含量与色谱峰面积在0~2.0μg/m L范围内线性良好,线性相关系数均在0.995以上,方法检出限为0.05 mg/L。16种邻苯二甲酸酯含量测定结果的相对标准偏差均小于10%(n=6),加标回收率为91.21%~105.22%。该方法样品前处理简单,灵敏度高,适用于同时定性及定量检测白酒中16种邻苯二甲酸酯。     

基于拉曼光谱法建立的模型快速预测布洛芬缓释胶囊中布洛芬的含量北大核心CSCD

为快速测定布洛芬缓释胶囊中布洛芬的含量,进行了题示项目研究。以高效液相色谱法(HPLC)为参比,采用拉曼光谱仪对5个校正集样本和布洛芬对照品进行扫描,将原始拉曼光谱图导入计算平台,选择波段250-1800 cm^(-1),通过荧光褪色差分法校正基线,二阶滤波求导进行降噪处理,用向量夹角转换算法计算各样本与布洛芬对照品拉曼光谱之间夹角余弦的方差值,以布洛芬的质量分数对该值进行拟合,得到模型的关联方程。采集待测样品的拉曼光谱,利用建立的模型预测其中布洛芬的含量。结果显示:布洛芬的质量分数在55%~90%内与其对应的夹角余弦的方差值呈线性关系;验证集样本的预测值与HPLC所得参考值的相对偏差为3.0%~3.8%。模型用于实际样品分析,预测值和参考值的相对偏差为1.2%~6.8%,预测值的相对标准偏差(n=5)为0.99%~3.1%。     

拉曼光谱法定量分析焦磷酸根离子的含量

应用拉曼光谱技术研究了焦磷酸钾、硝酸钾、磷酸二氢钾、乙二胺四乙酸钠等十余种可溶性盐水溶液以及它们的混合物溶液的拉曼光谱特征,考察了共存组分对焦磷酸根拉曼光谱特征峰的影响;建立了基于拉曼光谱技术定量分析溶液中焦磷酸根离子含量的方法。结果表明,以硝酸钾为内标物,保持被测溶液pH 11,焦磷酸根离子拉曼光谱特征峰强度与硝酸根离子拉曼光谱特征峰强度之比值对焦磷酸根浓度呈良好的线性关系,所得线性回归方程为y=1.2110x+0.1515,相关系数R2=0.9996;已经研究过的十余种可溶性盐共存物几乎不干扰焦磷酸根离子的定量分析。     

Electronic and vibrational spectra of Mn rich sursassite

The optical spectrum of Mn2+ in octahedral coordination for sursassite is characterized by well resolved bands at 580, 515, 470, 390, 340, and 295 nm (17240, 19420, 21280, 25640, 29410 and 33900 cm-1). Crystal field parameters evaluated from the observed bands are Dq=690, B=680 and C=2800 cm-1. A broad band centred around 13000 cm-1 attributed to Fe(III) ion is an impurity in sursassite confirmed from EDX analysis. Vibrational spectra have been investigated both by IR and Raman spectroscopy. The correlation between vibrational modes and the structural properties of the manganese silicate, sursassite, is made and compared with other silicates. Two vibrational modes of CO(3)2- observed; the antisymmetric stretching mode (nu3) at 1420 cm-1 (IR active) and the out-of-plane bending mode (nu2) (IR and Raman active) at approximately 875 cm-1. This confirms the Mn rich phases in sursassite as observed from SEM probably an Mn carbonate-rhodochrosite.     

Quantitative Determination of Glycine,Alanine, Aspartic Acid,Glutamic Acid,Phenylalanine, and Tryptophan by Raman Spectroscopy

The development of a new quantitative method for amino acids using Raman spectroscopy is reported. Raman spectra of glycine, alanine, aspartic acid, glutamic acid, phenylalanine, and tryptophan were measured. The band ratio between the Raman intensity of the amino acid and that of acetonitrile as an external standard was calculated to remove the influence of factors such as laser power intensity and instrumental effects. The calibration curves were obtained by plotting the band ratios against the concentrations of the amino acids. The curves were linear with coefficient correlations of over 0.99 for all amino acids. The Raman spectra of known concentration samples were measured to confirm the reproducibility of this method. The relative errors were small, indicating that the concentrations of amino acids can be determined using Raman spectroscopy. The limits of detection and quantitation were determined as thrice and 10 times the standard deviation of the background signal to be 0.007 and 0.02?mol?L^?1, respectively. Raman spectra of aspartic acid at 0.02?mol?L^?1 were measured several times and the uncertainty was 7%.     

Quantitative determination by temperature dependent near-infrared spectra: a further study

Quantitative spectra-temperature relationship (QSTR) between near-infrared (NIR) spectra and temperature has been studied in our previous work (Talanta, 2010, 82, 1017-1021). In this study, applicability of the QSTR model for quantitative determination is further studied using the spectra of aqueous ethanol samples in the temperature range of 31-40 °C and the concentration range of 1-99%. The results show that QSTR model can be built by using the spectra in a small temperature range and the quantitative analysis can be achieved by only two spectra at different temperatures. Moreover, calibration curves for different concentration ranges (1-5%, 20-70%, 95-99%, v/v) are investigated by using linear and nonlinear curve fitting, respectively. Both of the linear and nonlinear curves are found to be applicable within these concentration ranges. Therefore, the temperature dependent NIR spectra may provide a new way for quantitative determination and may have high potential in bio-fluids analysis or industrial practices.     

无定型氧化硅转变为α-方石英的振动光谱

红外和喇曼光谱是分子结构信息的重要来源,也是研究表面和催化问题的强有力手段,常用来表征活性中心及吸附物种的结构．为提高稳定性,催化剂一般都要经过焙烧处理,在焙烧过程中,载体结构可能会发生变化,有时还会形成一定的晶相．载体结构变化时,一般会伴随振动光谱的变化,因此在利用振动光谱研究催化体系时,弄清载体的振动光谱是十分必要的．二氧化硅是最常用的催化剂载体之一,但它具有比较多的结构形式,除无定型氧化硅中硅氧四面体可连接成不同的结构外,它还具有石英、鳞石英、方石英等多个晶相系列．对氧化硅的不同结构形式,…     

Semi-quantitative analysis of indigo carmine,using silver colloids,by surface enhanced resonance Raman spectroscopy (SERRS)

The application of surface enhanced resonance Raman spectroscopy (SERRS) to the semi-quantitative analysis of the dye, indigo carmine, has been examined using citrate-reduced silver colloids. Good linear correlations are observed for the dye band at 1580 cm(-1) in the concentration range 10(-7)-10(-5) and 10(-9)-10(-5) mol dm(-3), using laser exciting wavelengths of 514.5 [(R=0.9983)] and 632.8 nm [(R=0.9978)], respectively. At concentrations of dye above 10(-6) M the concentration dependence of the SERRS signals is non-linear due to the coverage of the surface of the colloidal particles by the dye being in excess of a full monolayer. At concentrations above 10(-6) M resonance Raman spectroscopy (RRS) can be employed for the quantitative analysis of the dye. An internal standard was used and a good linear correlation (R=0.997) was observed for the dependence of dye signal intensities at 1580 cm(-1) in the concentration range 10(-5)-10(-4) M using a laser exciting wavelength of 514.5 nm. The limits of detection of indigo carmine by SERRS (514.5 nm), SERRS (632.8 nm) and solution RRS (514.5 nm) are found to be 0.9, 1 and 38 ppm, respectively.     

不同电解质体系水的拉曼谱的研究

通过一系列电解质体系水的拉曼光谱测量，得到了阴、阳离子种类和浓度引起的水伸缩振动和弯曲振动谱带丰富的变化信息，ＣｌＯ４＾－能有效地破坏水分子间的氢键，随着ＣｌＯ４浓度的增加，水分子间的氢键并非逐步被打断，而是氢键被破坏的水分子越来越多，从而使水分子有序度增大，这种氢键破坏方式符合水的混合模型（ＭｉｘｔｕｒｅＭｏｄｅｌ）ＳＯ＾２－４浓度的增对水的Ｒａｍａｎ光谱影响较小，是由于ＳＯ＾２－４与水分了间的     

Hydrogen-bonding between pyrimidine and water: a vibrational spectroscopic analysis

We present an experimental and a theoretical study on hydrogen-bonding between pyrimidine and water as the H-donor. The degree of hydrogen-bonding in this binary system varies with mixture composition. This was monitored experimentally by polarization-resolved linear Raman spectroscopy with the pyrimidine ring breathing mode nu1 as a marker band. A subsequent quantitative line shape analysis of the isotropic Raman intensity for 24 pyrimidine/water mixtures clearly revealed a splitting into three spectral components upon dilution with water. The two additional peaks have been assigned to distinct groups of hydrogen-bonded species that differ in the number of pyrimidine nitrogen atoms (N) involved in hydrogen-bonding to water hydrogen atoms (H). From the integrated Raman intensities for "free" and "hydrogen-bonded" pyrimidine, a concentration profile for these species was established. Our assignments and interpretations are supported by quantum mechanical calculations of structures and by vibrational spectra for pyrimidine and 10 pyrimidine/water complexes with increasing water content. Also, accurate structure-spectra correlations for different cluster subgroups have been determined; within each particular cluster subgroup the water content varies, and a perfect negative correlation between NH hydrogen-bond distances and nu1 wavenumbers was observed.     

Raman Spectroscopic Determination of the Degree of Cationic Modification in Waxy Maize Starches

ABSTRACT

Waxy (essentially amylose-free) maize starch was chemically modified to varying degrees by treatment with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC), and the degree of cationic modification was determined by a standard wet chemistry method. FT-Raman spectra of the modified starches were taken, and a characteristic Raman band ～761 cm^?1 was found. This 761 cm^?1 Raman band's intensity depended on the level of cationic modification of the starch. The ratio of intensity of the ～761 cm^?1 band to a ～715 cm^?1 C-C stretch Raman band (used as an internal standard) was plotted versus the amount of cationic modification derived by titration analysis, and a linear fit was obtained with a correlation of 0.998. The FT-Raman spectroscopy method presented here demonstrates a rapid non-destructive way to determine the level of cationic modification of waxy maize starch, and should be suitable for use with cationic modified starches of any amylose content.     

基于非接触式拉曼光谱分析人血与犬血的PCA-LDA鉴别方法

将拉曼光谱分析法与数理统计方法有机结合,构建人血与犬血种属判别模型,实现了不同种属血液样本的高效无损鉴别.采用拉曼光谱的无损测试模式对血液样本进行测试,考察了抗凝管管材、聚焦位置及曝光时间等对血液样本拉曼光谱的影响,在激发波长为632.8 nm,光谱扫描范围为200~1800 cm-1,功率衰减率50%,曝光时间5 s及累加次数为2次的优化条件下,获得了无损检测条件下的血液样本拉曼光谱图.针对血液样本组分复杂、拉曼光谱信号基底背景高等问题,提出了基于小波变换去噪,进行分段多项式基线校正的预处理方法,有效解决了血液样本拉曼光谱谱图的高噪音和基线漂移问题.实验选择30例正常人血和33例比格犬血为样本训练集,5例正常人血和5例比格犬血为测试集,基于主成分分析法(PCA)联合线性判别法(LDA)模型,训练集分类正确率达到95.23%,盲测集分类正确率达90.00%.这种基于非接触式血液样本拉曼光谱和PCA-LDA判断模型的测试方法在进出口检验检疫等涉及血液无损鉴别的领域具有广泛的应用价值和前景.