Comparative Study of Two Methods of Orthogonal Double-Pulse Laser-Induced Breakdown Spectroscopy of Aluminum

Double-pulse laser induced breakdown spectroscopy (DP-LIBS) of aluminum sample is studied experimentally in orthogonal configuration in air. In this configuration, two schemes of reheating and pre-ablation are examined and the results are compared with single pulse one. The effect of delay time between two laser pulses on emission line intensities of plasma is investigated. Some of the parameters that have been involved in different mechanism of signal enhancement such as plasma temperature, sample heating effects, atmospheric effects, and modification of the ablation dynamics are more discussed. Investigation of the effect of laser pulse energy on emission line intensities in single pulse LIBS experiment demonstrate that because of saturation effects the intensities will not increase necessarily by increasing the laser pulse energy. Moreover, the results show that the electron temperature and rate of mass removal in orthogonal configuration of DP-LIBS is higher than that of single pulse with the same total energy. It is suggested that for correct comparison between single and double pulse results, the optimum pulse energy in single pulse should be considered. Overall, our results demonstrate that under optimized conditions the signal enhancement is much more in pre-ablation configuration than re-heating configuration.     

农田土壤中钾元素含量的激光诱导击穿光谱测量方法

农田土壤中钾元素的实时测量具有重要的意义。利用由1 064 nm激光器、高分辨率光谱仪组成的激光诱导击穿光谱系统,研究了土壤总钾含量的LIBS测量方法。文章对钾元素含量在8.74～34.56 g·kg-1之间的农田土壤样品进行分析,比较了404.40,404.72,766.49和769.90 nm的钾原子特征谱线,并选取766.49 nm为本研究的分析谱线。分析了激光器稳定性、随机噪声造成的谱线强度误差,并以农田土壤中含量相对稳定的硅元素为参照元素,建立K和Si光谱强度比值与土壤中K元素含量关系的内定标模型。定标曲线拟合相关系数为0.935,定标模型对预测集样品的预测标准偏差为9.26%。     

应用激光诱导击穿光谱检测污水溶液中的砷

工业冶炼过程中产生的废水中含有As等重金属元素,对环境造成污染并对人类身体健康形成危害,有必要对其进行实时、在线的监测。激光诱导击穿光谱(LIBS)是一种新型的元素测量技术,具有快速检测等优点。文章作者搭建了一套激光诱导击穿光谱实验装置,采用Nd∶YAG激光器产生的脉冲激光击穿样品产生等离子体,其发射的光谱被中阶梯光栅光谱仪分光,并用ICCD进行光电探测。对从现场采集的含砷工业废水开展了LIBS探测实验,并定性分析出了As元素的特征谱线。根据一系列含As浓度不同的污水样品的LIBS实验结果,获得元素浓度与谱线强度的关系曲线(定标曲线)。采用定标曲线可以对未知含As浓度的工业废水进行定量分析。结果表明,采用LIBS方法能够实现对污水溶液中的As元素的快速检测,具有广泛的应用前景。     

水溶液中微量Cu元素的激光诱导光谱检测

采用普通打印纸作为基底置于含有痕量重金属离子的水溶液中,用于富集溶液中的重金属Cu元素,烘干后用激光诱导击穿光谱进行定量分析。该方法克服了用激光诱导击穿光谱方法直接分析液相样品中重金属含量时存在水的溅射和灵敏度低等不足。实验中选用324.7 nm的光谱线作为分析线,研究了光谱强度与富集时间的关系,建立了用于溶液中Cu元素定量测量的校正曲线,检测限达到0.023 mg·L-1。为水体中重金属检测提供了一个可行的具有良好灵敏度分析技术。     

激光诱导击穿光谱分析钢中酸不溶铝含量

激光诱导击穿光谱(LIBS)具有分析速度快、非接触测量、表面微区分析以及易于实现在线实时监控分析等优点。通过LIBS对块状钢铁样品表面进行扫描分析,实现了钢中酸不溶铝含量的定量表征。铝的异常信号采用Nalimov迭代法剔除,以剩余信号强度的平均值加三倍标准偏差作为阈值强度,高于阈值强度的信号认为由酸不溶铝产生,反之由酸溶铝产生。在用含量校准曲线获得钢中总铝的含量后,分别根据酸不溶铝信号总强度或信号总个数与总铝信号之比,计算钢中酸不溶铝的含量。几种钢铁标准样品及实际生产板坯样品中酸不溶铝含量的对比分析结果表明,根据铝信号总强度获得的分析结果与传统湿法分析结果吻合得更好,可用于快速定量表征钢中酸不溶铝的含量。     

基于激光诱导击穿光谱技术检测分析原铝中硅、铁元素含量

利用自行搭建的LIBS装置对原铝中硅铁含量进行了分析测试,测试前对原铝试样进行了微观形貌分析,研究发现原铝中硅元素除有个别区域聚团现象外,其分布相对较为均匀;铁元素多以团状汇聚形态出现,且无明显的分布规律。实验分别考察了激光脉冲能量对激光诱导原铝等离子体光谱的影响,发现随着激光脉冲能量的增大,硅、铁元素信噪比先增加后减小,硅、铁谱线信噪比最大值均出现在160 mJ处,实验选取的激光脉冲能量为160 mJ。在上述较为合理的实验条件下,以内标法为基础,分别采用两种标样（纯铝标样与自选标样）建立了定标模型;结果表明：相比于纯铝标准试样,采用自选试样建立的定标模型不够理想,且数据的离散程度较大,铁元素直线拟合优度仅为0.921 3,相对标准偏差也较大。采用纯铝标样时,在试样不旋转的情况下,硅、铁元素定标曲线拟合优度分别为0.961 1与0.974 1,相对标准偏差分别为8.85%与9.43%,且误差棒显示误差随定标试样的硅、铁含量升高而增大。当试样台保持转速50 r·min-1条件下进行实验,发现硅、铁元素定标曲线的拟合优度分别为0.978 5与0.988,相对标准偏差分别为3.78%与3.4%,相比于试样平台固定情况下的定标结果,拟合优度明显改善,相对标准偏差也有所降低,定标模型明显优于自选试样建立的模型。使用两种定标模型对25个测试样进行了分析测试,比较了两种测试结果的相对误差,纯铝定标试样由于含量梯度较大,跨度较宽,采用该标样建立的定标模型对低铁原铝试样测试适应性相对较差,而自选试样建立的定标模型虽然不够理想,但针对低铁原铝试样的测试适应性相对较好。对激光诱导原铝产生的等离子体进行了诊断,通过镁元素几条离子谱线的玻耳兹曼图,计算出了等离子体温度约为9 163.63 K,利用镁元素一条谱线的Stark展宽估算出等离子体电子密度为1.69×1017 cm-3,验证了激光诱导原铝等离子体处于局部热力学平衡状态的假设是成立的。     

Determination of Chloride Content in Different Types of Cement Using Laser-Induced Breakdown Spectroscopy

The characterization and accurate determination of the chloride content in cement/concrete is very important for the assessment of the durability and safety of a concrete structure. The available analytical techniques are relatively expensive and time consuming. In this study, a laser-induced breakdown spectroscopy (LIBS) system was used for determination of elemental composition in three different types of cement samples. The plasma was generated by focusing a pulsed Nd: YAG laser at 1064 nm on the cement samples. The concentrations of different elements of significance for structural stability in cement samples were determined. The evaluation of the potential and the capabilities of LIBS as a rapid tool for characterization of cement samples is discussed. The optimum LIBS setup and experimental conditions to detect and measure chloride in building materials are reported. The LIBS results were compared with the results obtained using a standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP–ES). The limits of detection were determined, and calibration curves were measured. The results of this investigation indicate the reliability of LIBS to characterize different cement samples and to assess the chloride content in these cements.     

Laser-Induced Breakdown Spectroscopy: An Approach to Detect Adulteration in Turmeric

In the present paper, four turmeric samples, A, B, C, and D, were analyzed using the laser-induced breakdown spectroscopic (LIBS) technique. Laser-induced breakdown spectra of A, B, and C give the spectral lines of elements such as carbon, sodium, potassium, magnesium, calcium, iron, and molecular bands of CN, whereas spectral signatures of the toxic elements lead and chromium are also present in sample D, demonstrating the adulteration in it. Principal component analysis of the LIBS data of the turmeric samples has been used for instant discrimination. The plots and principal components provide clusters belonging to two groups, enabling laser-induced breakdown spectroscopic data along with principal component analysis to be used as an instant monitoring tool.     

Determination of the Mn/Fe Ratio in Ferromanganese Nodules Using Calibration-Free Laser-Induced Breakdown Spectroscopy

Optics and Spectroscopy - The Mn/Fe ratio in ferromanganese nodules is determined by calibration-free laser-induced breakdown spectroscopy based on the use of only the plasma temperature and...     

激光诱导击穿光谱技术的研究与应用新进展

激光诱导击穿光谱技术(LIBS)是一种近年来随着激光技术和光谱检测技术的发展而兴起的对元素定性和定量分析的光谱技术。详细介绍了LIBS技术最新的研究发展情况,以及在冶金、环境污染检测、生物医学、植物学、空间探索等领域的最新应用进展。     

电感耦合等离子体发射光谱法测定汽油中的氯

应用电感耦合等离子体发射光谱法(ICP-AES)建立了定量分析车用汽油中氯的新方法。方法选择航空煤油作为稀释剂,按稀释剂：样品为4∶1(体积比)进行稀释。选取波长134.724 nm为分析谱线,在辅助气中引入0.050 L·min-1氧气,有效的消除积碳,保持等离子体稳定。方法考察了发射功率,雾化气流量,辅助气流量以及氧气流量对氯信背比的影响,确定了ICP-AES的最佳分析条件,通过标准加入法校正基体效应和信号漂移对测量所造成的影响。方法的加标回收率在96.6％～103.9％之间,相对标准偏差(RSD,n=10) 在1.57%～4.49%之间,方法检出限为0.27 mg·L-1。此方法和微库仑法对样品中有机氯的测定结果基本一致,而且,该方法具有不受元素的存在形态限制的优点,测定的结果为总氯(有机氯和无机氯)含量。方法简便,快速,灵敏,拓展了ICP-AES在非金属元素特别是卤素分析方面的应用,可用于车用汽油中氯含量的日常检测,为车用汽油的质量评价提供技术保障。     

采用ICP-MS/MS准确测定食品中钙和氯

建立利用电感耦合等离子体串联质谱测定食品中钙和氯的分析方法。针对Ca的高丰度同位素40Ca受到来自等离子气40Ar的干扰,35Cl受到来自16O18OH的严重干扰,在MS/MS模式下,利用碰撞/反应池技术,以H₂为反应气,使40Ar+与H₂发生反应,而40Ca+不与H₂发生反应,利用H₂原位质量法消除40Ar+对40Ca+的干扰;而35Cl+则能与H₂发生质量转移反应生成H₂35Cl+,通过测定H₂35Cl+消除16O18OH+对35Cl+的干扰。Ca和Cl在0.0~100.0 μg·L-1的浓度范围内线性关系良好,线性相关系数（R2）≥0.999 9,Ca和Cl的检出限分别为0.061和2.32 μg·L-1。采用系列国家标准物质验证了对方法的准确性和精密度,其测定结果与标准参考物质的认定值基本一致,表明方法的准确性好、精密度高。所建立的新方法可实现食品中钙和氯的准确测定。     

用激光诱导击穿光谱技术比较土豆和百合中的微量元素

激光诱导击穿光谱(LIBS)已成功地运用于固体、液体、气体样品中微量元素的测量以及微生物、细菌等的鉴别分析上,而在植物样品上面的应用则是一个较新的课题。该实验用纳秒Nd∶YAG激光器击穿真空冻干的土豆、百合样品,用光纤光谱仪测量了其LIBS光谱。通过鉴别、分析LIBS光谱,得到了这两种样品中微量元素的成分。并且对土豆干和百合干中Ca,Na,K,Fe,Al,Mg六种金属元素典型谱线的强度进行了统计分析,并由此得到了样品中这六种微量元素含量的对比情况。实验结果表明土豆干中的Ca和Na等含量都明显高于百合干,而百合干中Mg的含量较高。实验结果还表明用LIBS技术检测、对比冻干植物样品中微量元素含量是一种快速、有效的分析方法。     

真空环境熔融金属成分检测的激光诱导击穿光谱系统

激光诱导击穿光谱(LIBS)技术是应用于冶金在线分析最具前景的技术之一。为了研究真空和高温条件下LIBS光谱特性和物质成分定量分析方法,设计并搭建了可实现真空环境高温熔融金属LIBS光谱测量的实验系统。系统以调Q Nd: YAG脉冲激光器为光源,采用不同焦距透镜实现激光聚焦和信号光采集,并利用光谱仪进行光谱检测,真空获取和高温加热通过真空泵和中频感应电炉实现,感应加热线圈通过陶瓷封接引线法兰与真空系统进行整合。经过安装测试,搭建系统在未加热情况下真空度可达1×10-4Pa,加热温度可达到1 600 ℃,可实现真空环境下铁、铝等金属加热或熔融,并获得相应环境下的LIBS测量光谱。利用该系统进行真空和熔融条件下标准钢样品的LIBS实验,得到了固态钢样品LIBS光谱在不同真空度下的光谱对比,以及真空环境熔融态和固态钢样品光谱对比。通过对测得的LIBS光谱进行数据处理和理论分析,所得初步实验结果与现有研究结论相符合,表明该系统工作状况良好,可满足真空环境下的熔融金属成分分析研究的基本需求。     

On Sensitivity and Detection Limit with Reference to Flame Spectrometry

Apparently and amazingly, the concepts of sensitivity and detection limit are still a matter of debate among flame spectroscopists. Probably the papers on this issue by Willis¹ and West² and certainly some misleading statements would have been left unwritten, if these authors had taken the elementary precaution of consulting the pertinent literature^3-7 or an appropriate textbook⁸. Surely there is no need to resort to “normal English usage”² when discussing well-defined scientific concepts. No doubt, most of the confusion stems from the fact that the pioneering articles have been written in German and from the lack of a consistent English, terminology. One frightening example is offered by Ramirez-Muñoz⁹ who introduces no less than sixteen different terms, freely interchanging sensitivity and detection limit. But perhaps, it is not too late to restore the damage.     

窗口可变滑动相关分析方法在激光诱导击穿光谱谱线自动识别中的应用

激光诱导击穿光谱(LIBS)谱线具有很窄的展宽,且光谱仪因外界温度条件的变化存在波长漂移,光谱数据为离散数字信号,受噪声、谱线重叠及连续背景的影响,信号存在失真和变形。而目前光谱仪自带谱线识别分析软件主要以"就近原则"为主,错误率较高,必须依赖于人眼的观察对比。针对这个问题,在研究LIBS光谱特性的基础上,提出了一种窗口可变滑动相关分析方法(CAASW),用于激光诱导击穿光谱谱线自动识别。以土壤标准物质为样品,对该方法进行了实验分析和评价,与光谱仪自带分析识别软件相比,CAASW明显提高了识别准确率和识别速度,最终实现了谱线的自动识别。