激光诱导击穿光谱快速定量检测橘子中 铅含量的初步研究

目的利用激光诱导击穿光谱技术对橘子中铅含量进行快速定量检测。方法将普通的橘子样品进行铅溶液污染处理,利用原子吸收法测定样品中铅元素含量作为参考浓度,通过分析橘子中铅元素的激光诱导击穿光谱特征谱线,结合NIST标准数据库,得出铅元素的激光诱导击穿光谱显著的波长为363.958 nm、368.348 nm、405.783 nm,并确定以405.783 nm作为定量分析铅元素特征波长的方法。结果分析实验中的不同浓度样品的光谱信息,拟合得到铅元素的LIBS特征谱线强度和铅元素浓度的定量分析曲线,其中拟合曲线的相关系数为0.98195,分析定标模型得出该模型不适用于浓度小于10μg/g样品,根据检出限公式得到检测限(D.L)的值为12.98μg/g。结论研究结果表明该激光技术在农产品重金属检测以各种样品中的元素含量检测方面具有很大的前景。     

定量分析宝石材料化学成分的激光诱导离解光谱方法研究

主要针对宝石材料进行了激光诱导离解光谱技术定量分析方法的总结以及对比研究。选择外标法、自由定标法和归一化的外标法三种较为适用于宝石材料分析的方法进行了介绍。选取陨石玻璃、绿辉石、紫色翡翠以及硅酸盐玻璃等成分较为均匀的样品作为分析对象,使用中国地质大学(武汉)珠宝学院自制的激光诱导离解光谱设备,分别运用三种方法对其进行了定量分析的计算。定量分析结果显示,外标法易受成分变化及结构差异而造成的基体效应的影响,分析的准确度不高;自由定标法在分析成分复杂的样品时,其影响因素十分复杂,会产生较大的误差;归一化的外标法可有效校正基体效应的影响,其定量分析结果要优于前两者,虽然在微量元素分析准确度上尚需改进,但不失为一种较好的快速定量分析宝石材料的定量分析方法。     

基于激光诱导击穿光谱技术分析鳕鱼中8种元素含量

应用激光诱导击穿光谱(laser induced breakdown spectroscopy,LIBS)技术结合单变量定标法、内定标法和偏最小二乘(partial least square,PLS)法对鳕鱼中的P、Fe、Al、Mn、K、Mg、Ca、Na共8种元素进行同时定量分析。制备鳕鱼标准系列,采用电感耦合等离子体发射光谱提供各元素含量的参考值。对鱼肉样品进行压片处理,采集其LIBS光谱,选取各元素特征谱线,并对单变量定标、内定标与PLS 3种定量方法进行比较。结果表明,PLS法优于传统的单变量定标法和内定标法,具有较高的预测准确度和精度,对各元素预测含量的相对误差范围在0.96%～13.27%之间,相对标准偏差范围在2.02%～7.55%之间。结果表明LIBS技术在鳕鱼中多种元素的快速、非定向检测方面具有很大的应用潜力,并可以推广至水产品的快速检测分析,同时为今后开发便携式LIBS水产品检测仪器提供理论依据。     

自由定标法在激光诱导等离子光谱中的应用

激光诱导等离子体光谱(LIBS)技术是一种应用非常广泛的光谱检测技术。相比于其他的测量方法,LIBS技术更适应于实时多变的测量环境。但是由于检测过程中样品的基体效应,LIBS技术很难对样品进行定性测量。文章主要介绍一种有效的定量检测方法———自由定标法。并且通过一个具体的实验来验证自由定标法可行性。     

基于近红外光谱法的鱼粉快速判别

基于近红外漫反射光谱分析技术对市场上常见的淡水鱼粉、进口鱼粉和国产鱼粉3 类商品化的鱼粉样品进行自动化判别实验。通过分析鱼粉样品光谱之间的差异,采用主成分分析法建立鱼粉种类的定性判别的分类模型,光谱范围为波长1 100～2 498 nm,交互定标决定系数为0.913 5,交互定标标准误差为0.133 8。通过对验证样品的分析,建立的判别模型预判准确率达到84.6%,外部验证准确率达到100%。结果表明,近红外光谱技术结合化学计量学法可以作为一种快速、无损、可靠的方法用于鱼粉种类的判别。     

激光诱导击穿光谱在乳制品质量检测中的应用

乳制品是人体健康必需营养的重要来源之一,因此保证乳制品的质量和安全至关重要。作为一种新型的激光烧蚀原子发射光谱技术,激光诱导击穿光谱已经在乳制品的定性和定量分析方面展现出了巨大的应用潜力。本文简要介绍了激光诱导击穿光谱的检测原理,综述了激光诱导击穿光谱在乳制品中矿物质元素、重金属元素、脂肪和蛋白质含量,以及牛奶掺假物检测方面的最新研究进展。最后,探讨了激光诱导击穿光谱在乳制品质量检测方面存在的问题并对其发展趋势进行了展望。     

采用近红外光谱进行采后苹果品种及货架期定性判别

运用近红外光谱技术,通过不同光谱预处理和不同光谱波段选择,研究苹果品种(嘎啦、乔纳金、金冠、寒富)及货架期(0、14、28 d)的近红外判别模型。结果表明,不同品种苹果定标判别模型最优光谱预处理方法为:在全波长范围(408. 8～2 492. 8 nm)内,采用去散射结合二阶导数光谱预处理,对未知样品判别正确率为85. 00%～95. 00%;苹果货架期较优定标模型在1 108～2 492. 8 nm范围内,光谱预处理方法为标准正常化处理(standard normal variate,SNV)+去散射处理(detrend,D)+一阶导数,预测样品正确率为91. 67%～96. 67%。实验证明,近红外光谱技术对采后苹果品种及货架期检测具有适用性。     

吉林蛇纹石玉特征初步研究

对产自吉林省白山市抚松县沿江乡的蛇纹石玉样品分别从地质背景、激光诱导离解光谱、X射线粉末衍射和红外吸收光谱等方面进行了研究,并与辽宁岫玉样品进行了对比.结果表明,吉林蛇纹石玉样品的主要颜色为深浅不一的绿色,主要含Si,Al,Cr,Fe,Mn,Mg,Ca,Sr和Na等元素,其中Ca与Mg的谱线较强,A1,Mn与Sr的质量分数少;X射线粉末衍射结果显示,样品的主要矿物组成为纤蛇纹石,红外光谱结果也显示了其具有纤蛇纹石峰值的特征.     

胭脂螺外骨骼的宝石学特征

胭脂螺是一种颜色鲜艳,极具经济价值的观赏性海螺,近年在文玩珠宝界中越来越流行,其价值超过了市场中流行的砗磲,万宝螺等其他相似的有机宝石。本文选取了市场购买的胭脂螺外骨骼样品为研究对象,使用宝石显微镜,X射线衍射光谱仪,激光拉曼光谱仪,显微红外光谱仪及激光诱导离解光谱仪对胭脂螺外骨骼的宝石学特征进行了研究,以探究胭脂螺外骨骼的化学成分和结构,为其以后的研究发展提供一定的理论基础。结果表明:胭脂螺外骨骼的主要矿物组成是文石,内部存在棱柱状、条带状、纤维状等生物结构。不同色层具有相似的元素及质量分数,颜色成因可能与致色元素无关,而与有机物的种类及质量分数相关。红外光谱的半定量分析结果表明,粉色区域有机物相对质量分数较高;橙色,黄色区域质量分数居中;白色区域质量分数最低。结合其他测试数据,推测不同种类的有机物产生了不同颜色的胭脂螺外骨骼区域,黄色橙色的成因与金属卟啉有关,粉色的成因则与类胡萝卜素有关。     

新疆宝石级锂云母岩的矿物学特征研究

为了探究新疆一种商业名为“丁香紫玉”材料的宝石学特征及谱学特征,针对5块产自新疆阿尔泰的样品进行了常规检测,采用X射线粉末衍射仪、激光拉曼光谱仪、傅里叶红外变换光谱仪和激光诱导离解光谱仪等仪器测试分析,从矿物组成、拉曼光谱和红外光谱以及化学元素组成进行了研究分析。测试结果表明“丁香紫玉”为宝石级锂云母岩。X射线粉末衍射分析结果表明样品的主要矿物组成为云母,占90%左右,次要矿物钠长石（10%左右）以及微量石英。激光拉曼光谱测试结果显示,其谱峰在高波数3 000～3 800cm＾-1区域有3 628,3 496cm＾-1羟基的伸缩振动所致谱峰。红外光谱测试结果,在高波数的羟基伸缩振动吸收带在3 625,3 454cm＾-1与拉曼测试的羟基伸缩振动带结果基本相同。激光诱导离解光谱显示样品主要组成元素为H、Li、Na、K、Cs、Ca、Mg、Al、Si,微量元素有Be、Ti、Fe、Mn、Cu、Cr、Hg、Pd等。     

SERS结合PCA-LDA分析鉴别鸡肉中硝基呋喃类代谢物的混合残留

以纳米Au溶胶和NaCl溶液为活性增强基底,对鸡肉中残留的两种呋喃它酮代谢物(AMOZ)和呋喃妥因代谢物(AHD)进行表面增强拉曼光谱(SERS)快速检测技术研究。采用自适应迭代惩罚最小二乘法消除原始数据中的背景干扰,应用标准归一化进行光谱预处理,并结合主成分—线性判别方法(PCA-LDA)建立识别模型,得出模型校正集的判别正确率为90.48%,预测集的判别正确率为94.29%。研究表明,SERS技术与PCA-LDA相结合可以有效地鉴别出鸡肉样本中残留的AMOZ和AHD。     

Development of a rapid method based on front-face fluorescence spectroscopy for the monitoring of egg freshness: 2—evolution of egg yolk

This preliminary study is devoted to the application of front-face fluorescence spectroscopy to the study of egg yolks during storage. A total of 79 eggs stored for 1, 2, 3, 4, 5, 9, 10, 12, 16, 18, 23, 25 and 29 days at room temperature were analysed. The fluorescence emission spectra of tryptophan residues (excitation: 290 nm; emission: 305–430 nm) of proteins and the excitation spectra of vitamin A (emission: 410 nm; excitation: 270–350 nm) were recorded directly on egg yolk samples. Factorial discriminant analysis (FDA) was used to classify the eggs according to their date after they were laid. Using tryptophan fluorescence spectra, correct classification was observed for 57.1 and 51.9% for the calibration and the validation sets, respectively. Better classification (94.9 and 91.4% of the calibration and validation samples, respectively) was obtained from the vitamin A fluorescence spectra. The first five principal components (PCs) of the principal component analysis (PCA) extracted from each data set (tryptophan and vitamin A fluorescence spectra) were pooled (concatenated) into a single-matrix and analysed by FDA. Correct classifications were obtained for 97.5% of the calibration and 96.3.1% of the validation spectra. The discrimination of the investigated egg yolks according to their storage time was excellent. It was concluded that the concatenation of different fluorescence spectra might be considered as a promising indicator of shell egg freshness when they are used in egg products.     

A comparison and joint use of mid infrared and fluorescence spectroscopic methods for differentiating between manufacturing processes and sampling zones of ripened soft cheeses

Ten traditional M1 (n = 5) and M2 (n = 5) soft cheeses produced from raw milk, and five other stabilised M3 (n = 5) cheeses manufactured from pasteurised milk, were studied using mid infrared (MIR) and front face fluorescence (FFFS) spectroscopies. MIR (3000–900 cm⁻¹), tryptophan (excitation: 290 nm, emission: 305-450 nm), 400-640 emission spectra (excitation: 380 nm) and vitamin A (excitation: 280–350 nm, emission: 410 nm) spectra were recorded at two sampling zones (external (E) and central (C)) of the investigated cheeses. When the factorial discriminant analysis (FDA) was applied to the MIR spectra, the classification was not satisfactory. With tryptophan fluorescence spectra, correct classification of 94.4 and 69.4% was observed for the calibration and validation spectra, respectively. Better classification was obtained using vitamin A fluorescence spectra, since 91.8 and 80.6% of the calibration and validation spectra, respectively, were correctly classified. When the first five principal components (PCs) of the PCA extracted from each data set were pooled into a single matrix and analysed by FDA, the classification was considerably improved, obtaining a percentage of correct classification of 100 and 91.7% for the calibration and validation samples, respectively. It was concluded that concatenation of the physico-chemical and spectroscopic data sets is an efficient technique for the identification of soft cheese varieties.     

鸡腿肌冻干粉蛋氨酸近红外光谱定量预测模型的建立与优化

本文从光谱预处理方法、建模特征光谱筛选、异常样本剔除、建模样本选择四个方面建立和优化鸡腿肌冻干粉蛋氨酸近红外定量预测模型,旨在进一步提高模型的预测精度和模型稳健性。以263个鸡腿肌冻干粉NIRS和蛋氨酸含量为研究对象,分别使用7种不同光谱预处理方法、4种特征光谱筛选方法、2种MCCV异常样本剔除方法,SPXY和常规选择2种建模样本选择方法,应用偏最二小乘法(PLS)、内部交互验证和外部验证建立和优化腿肌冻干粉蛋氨酸近红外定量预测模型。结果表明：在本研究中,最优鸡腿肌冻干粉蛋氨酸NIRS定量预测模型为在1000-2502nm谱段,使用原始光谱,在SNV+gapsegment(1#,15,7)光谱的基础上使用MCCV方法删除54个样本后,采用SPXY方法选取156个校正样本,39个外部验证样本所建模型,其为0.93、SE_CV为0.0609、为0.83、RPD_P为2.42。研究表明,模型预测值与化学检测值有很高的相关度,对腿肌冻干粉蛋氨酸NIRS模型预测精度和稳健性影响最大因素是异常样本剔除方法和建模样本选取方法。     

Utilisation of a rapid technique based on front-face fluorescence spectroscopy for differentiating between fresh and frozen–thawed fish fillets

The potential of front-face fluorescence spectroscopy combined with chemometric tools was investigated to differentiate frozen–thawed from fresh fish. A total of 24 fish fillets, i.e., 12 fresh samples and 12 frozen–thawed samples, were investigated. Regarding the frozen–thawed samples, two speeds of freezing and thawing were tested (fast and slow) and for each condition, three whiting fillets were analysed. The fluorescence emission spectra of tryptophan (excitation: 290 nm, emission: 305–400 nm) and nicotinamide adenine dinucleotide (NADH) (excitation: 340 nm, emission: 360–570 nm) were recorded directly on samples. In a first step, the principal component analysis (PCA) was applied separately to the tryptophan or NADH fluorescence spectra. From the NADH spectra, PCA results showed a good discrimination between fresh and frozen–thawed fish samples. But it was not the case with the tryptophan fluorescence spectra. In a second step, factorial discriminant analysis (FDA) was applied to the first five principal components (PCs) of the PCA performed on the two data sets. Considering tryptophan fluorescence spectra, correct classification was observed for 62.5% and 70.8% of the calibration and validation spectra, respectively. A better classification was obtained from NADH fluorescence spectra since 100% correct classifications were obtained for the calibration and validation spectra. It was concluded that NADH fluorescence spectra may be considered as a promising probe for the reliable differentiation between frozen–thawed and fresh fish.     

金磁微粒的制备及其催化性能

采用水热法快速制备Fe₃O₄纳米粒子,并通过表面氨基化与金纳米粒子自组装方法构建金磁微粒（Fe₃O₄@Au）,优化金磁微粒的制备工艺,并表征其性能。结果表明,1%浓度的葡萄皮浸泡液制备金纳米粒子,其粒子平均粒径为7 nm,氨基化的Fe₃O₄纳米粒子可以有效固载金纳米粒子,最优制备工艺为:Fe₃O₄混悬液添加量2 m L,温度60℃,时间60 min。金磁微粒饱和磁化强度为61 emu/g,且具有良好的催化性能。      

利用光密度法对掺假豆浆的定性判别研究

蛋白质含量是豆浆品质评价的主要指标,实验运用近红外光谱技术获得83 个真伪豆浆的光谱,并对光谱图和光密度值进行统计分析,研究以蛋白质为主要定性指标的豆浆品质等级划分的可行性,建立豆浆品质定性判别的标准。结果显示：在波长742.59～810.96 nm范围内,随着豆浆样品蛋白质含量的升高,吸收光谱峰值变化越大。实验选取OD810.96 nm与OD742.59 nm做光密度差值分布图,根据83 个校正集样品的光密度差值分布图,确定豆浆两级判别的检测标准为：ΔOD742.59～810.96 nm大于0.062 9时,豆浆为不合格豆浆;ΔOD742.59～810.96 nm小于或等于0.062 9时,豆浆为合格豆浆。根据该判别标准对37 个预测集样品进行判别,17 个不合格豆浆全部被判别,正确判别率100%,20 个合格豆浆中有2 个被误判成不合格,误判率10%,预测结果准确率较高。实验应用光密度法进行豆浆品质的评价是可行的,方法简明、结果可靠,可为豆浆品质快速检测技术的应用提供一种参考方法。     

Spectroscopic studies of the biosorption of gold(III) by dealginated seaweed waste

Gold biosorption by dealginated seaweed waste has been studied to elucidate the mechanisms of metal uptake from solution. Dealginated seaweed was able to retain up to 1 mmol g(-1) of Au from solution at pH 3. FT-IR showed the presence of carboxylate groups on the surface of the biosorbent; however, the changes observed for the Au-bound samples suggested very little sorption to the carboxyl moieties. Colloidal Au formed on the surface of dealginated seaweed by reduction of Au(III) to Au(0) was observed using ESEM and four different types of particles were clearly identified. The Au distribution matched closely that obtained for S atoms indicating a possible link between these elements. EXAFS measurements showed that colloidal Au is present on the surface of the biosorbent. Evidence of gold reduction from Au(III) to Au(I) and Au(0) was also confirmed by the measured bond distances characteristic of the metal. The coordination number obtained by EXAFS indicated that approximately 75% of the Au on the sample was present in the colloidal form and the remaining Au was bound to S as nearest neighbor. The proposed mechanisms for Au removal from solution are reduction of Au species by components on the surface of the biosorbent to form colloidal metal followed by retention of the ionic Au(I) species at the sulfur containing sites. The results show that dealginated seaweed can be used for the cleanup of gold-containing effluents.     

Direct determination of oxidation state of gold deposits in metal-reducing bacterium Shewanella algae using X-ray absorption near-edge structure spectroscopy (XANES)

X-ray absorption near-edge structure spectroscopy (XANES) was successfully employed to determine the gold valence in the metal-reducing bacterium Shewanella algae after exposure to a 1 mM aqueous HAuCl4 solution for 10-120 min. XANES spectra revealed the oxidation state of gold in the bacterial cells to be Au(0) without any contribution from Au(III), demonstrating that S. algae cells can reduce AuCl4- ions to elemental gold. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis confirmed that gold nanoparticles 5-15 nm in size were deposited in the periplasmic space of the bacterial cells; a preferable, cell surface location for the easy recovery of biogenic nanoparticles.     

测汞仪原子吸收光谱法测定野生食用菌中的总汞

目的建立应用测汞仪直接测定野生食用菌中总汞含量的测定方法。方法样品经均质器粉碎,称量后,直接进样。样品在催化管内加热分解,在氧气的作用下,汞在齐化管内与金粉反应被捕集下来,形成金汞齐,再经高温使金汞齐分解成汞原子蒸气经载气带入吸收池,在253.7 nm处进行吸收测定。结果测汞仪检测方法线性范围:0.0~1000 ng/L,检出限为0.005 ng/m L,相关系数(R2)优于0.999,相对标准偏差(RSD)小于1.5%,回收率大于99%。结论用此仪器检测的方法无需进行样品前处理、进样量少、方法灵敏度高、精密度好、结果准确可靠、操作简单快速、没有试剂污染、检测速度快和运行成本不高,适用于野生食用菌中总汞的测定。