Classification of Chinese Herbal Medicine by Laser-Induced Breakdown Spectroscopy with Principal Component Analysis and Artificial Neural Network

Chinese herbal medicine has attracted increasing attention because of the unique and significant efficacy in various diseases. In this paper, three types of Chinese herbal medicine, the roots of Angelica pubescens, Codonopsis pilosula, and Ligusticum wallichii with different places of origin or parts, are analyzed and identified using laser-induced breakdown spectroscopy (LIBS) combined with principal component analysis (PCA) and artificial neural network (ANN). The study of the roots of A. pubescens was performed. The score matrix is obtained by principal component analysis, and the backpropagation artificial neural network (BP-ANN) model is established to identify the origin of the medicine based on LIBS spectroscopy of the roots of A. pubescens with three places of origin. The results show that the average classification accuracy is 99.89%, which exhibits better prediction of classification than linear discriminant analysis or support vector machine learning methods. To verify the effectiveness of PCA combined with the BP-ANN model, this method is used to identify the origin of C. pilosula. Meanwhile, the root and stem of L. wallichii are analyzed by the same method to distinguish the medicinal materials accurately. The recognition rate of C. pilosula is 95.83%, and that of L. wallichii is 99.85%. The results present that LIBS combined with PCA and BP-ANN is a useful tool for identification of Chinese herbal medicine and is expected to achieve automatic real-time, fast, and powerful measurements.     

Determination of Sulfite in Botanical Medicine Using Headspace Thin-Film Microextraction and Surface Enhanced Raman Spectrometry

A facile method using headspace thin-film microextraction (HS-TFME) coupled with surface enhanced Raman spectrometry (SERS) has been developed for the determination of sulfite in traditional Chinese herbal medicine. The extraction substrate was synthesized by depositing urchin-like ZnO micron particles on glass sheets using chemical liquid phase deposition. Under the optimal conditions, the intensity of the SERS signal at 630–640?cm^?1 provided a good linear relationship with the concentration of sulfite from 25 to 400?mg/kg, and the linear correlation coefficient (R) was 0.996 with a detection limit of 6?mg/kg. The method was employed for the determination of sulfite in herbal medicines, and the results were confirmed by a traditional distillation-titration method. Therefore, this developed HS-TFME-SERS method may play an important role in the rapid, simple, and selective determination of sulfite residues in Chinese herbal medicine and become a potentially universal method for this analyte in various solid samples.     

Enhanced Resolution of Copper and Bismuth by Addition of Gallium in Anodic Stripping Voltammetry with the Bismuth Film Electrode

This paper presents the enhanced analysis of copper on a bismuth electrode upon addition of gallium(III). The presence of gallium alleviates the problems of overlapping stripping signals usually observed between copper and bismuth when using the Bismuth Film Electrode. In addition, it has been found that the presence of gallium improves the reproducibility of the bismuth stripping signal. Simultaneous deposition of copper and bismuth at ?1500 mV for 2 minutes in a supporting electrolyte composed of 0.1 M pH 4.75 acetate buffer with 250 μg L^?1 gallium yields well resolved copper and bismuth signals when analyzed with square‐wave anodic stripping voltammetry. Simultaneous analysis of copper and lead yielded linear calibration plots in the range 10 to 100 μg L^?1 with regression coefficients of 0.997 and 0.994 respectively. The theoretical detection limit for copper was calculated to be 4.98 μg L^?1 utilizing a 2 minutes deposition time. The relative standard deviation for a copper concentration of 50 μg L^?1 was 1.6% (n=10).     

Novel Copper(II)-Selective Potentiometric Sensor Based on a Folic Acid-Functionalized Carbon Nanotube Material

Abstract

A folic acid-functionalized carbon nanotube nanomaterial was prepared by immobilizing folic acid molecules on the carbon nanotubes through covalent bonds. The material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Fourier transform infrared spectroscopy confirmed that folic acid molecules were grafted on the carbon nanotube surfaces through the amide bonds between the carboxylic acid functional groups of the oxidized carbon nanotubes and the amine groups of the folic acid molecules. The folic acid molecules bonded to carbon nanotube surfaces led to appreciable changes in the morphology. By using currently obtained folic acid-functionalized carbon nanotube nanomaterial as electroactive material in a polyvinyl chloride membrane, a potentiometric copper (II)-selective sensor was developed. Membrane optimization studies showed that the composition exhibiting the best potentiometric properties was 4.0% (w/w) folic acid–carbon nanotube, 64.0% (w/w) o-nitrophenyl octylether, and 32.0% (w/w) polyvinyl chloride. The developed sensor displayed a linear response in the copper (II) concentration ranging from 1.0?×?10^–6 to 1.0?×?10^–1 M with a correlation coefficient of 0.9993 and a slope of 29.8?±?0.6?mV/decade of activity. The response time, detection limit, and pH working range were determined to be 4?s, 3.8?×?10^–7 M and 4.0–8.0, respectively. The developed sensor showed highly selective and satisfactory potentiometric response for the determination of copper (II) in a Turkish coin.     

Filament-induced remote surface ablation for long range laser-induced breakdown spectroscopy operation

We demonstrate laser induced ablation and plasma line emission from a metallic target at distances up to 180 m from the laser, using filaments (self-guided propagation structures ∼ 100 μm in diameter and ∼ 5 × 10¹³ W/cm² in intensity) appearing as femtosecond and terawatt laser pulses propagating in air. The remarkable property of filaments to propagate over a long distance independently of the diffraction limit opens the frontier to long range operation of the laser-induced breakdown spectroscopy technique. We call this special configuration of remote laser-induced breakdown spectroscopy “remote filament-induced breakdown spectroscopy”. Our results show main features of filament-induced ablation on the surface of a metallic sample and associated plasma emission. Our experimental data allow us to estimate requirements for the detection system needed for kilometer-range remote filament-induced breakdown spectroscopy experiment.     

Determination of poisonous metals in wastewater collected from paint manufacturing plant using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) system was developed for determination of toxic metals in wastewater collected from local paint manufacturing plant. The plasma was generated by focusing a pulsed Nd:YAG laser at 1064 nm on the solid residue from wastewater collected from paint industry. The concentration of different elements of environmental significance like, lead, copper, chromium, calcium, sulphur, magnesium, zinc, titanium, strontium, nickel, silicone, iron, aluminum, barium, sodium, potassium and zirconium, in paint wastewater were 6, 3, 4, 301, 72, 200, 20, 42, 4, 1, 35, 120, 133, 119, 173, 28 and 12 mg kg⁻¹, respectively. The evaluation of potential and capabilities of LIBS as a rapid tool for paint industry effluent characterization is discussed in detail. Optimal experimental conditions were evaluated for improving the sensitivity of our LIBS system through parametric dependence study. The laser-induced breakdown spectroscopy (LIBS) results were compared with the results obtained using standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP). The relative accuracy of our LIBS system for various elements as compared with ICP method is in the range of 0.03-0.6 at 2.5% error confidence. Limits of detection (LOD) of our LIBS system were also estimated for the above mentioned elements.     

Calibration free laser-induced breakdown spectroscopy of oxide materials

The quantitative determination of oxide concentration by laser-induced breakdown spectroscopy is relevant in various fields of applications (e.g.: analysis of ores, concrete, slag). Calibration free laser-induced breakdown spectroscopy and the multivariate calibration are among the methods employed for quantitative concentration analysis of complex materials. We measured the intensity of neutral and ionized atomic emission lines of oxide materials by laser-induced breakdown spectroscopy and we modified the calibration free laser-induced breakdown spectroscopy method to increase the accuracy. The concentration of oxides was obtained by using stoichiometric relations. Sample materials were prepared from oxide powder (Fe₂O₃, MgO, CaO) by mixing and pressing. The concentration was 9.8–33.3 wt.% Fe₂O₃, 7.6–33.3 wt.% MgO and 33.3–81.2 wt.% CaO for different samples. Nd:YAG laser (wavelength 1064 nm, pulse duration ≈ 6 ns) ablation was performed in air. The laser-induced plasma emission was measured by an Echelle spectrometer equipped with a sensitivity calibrated ICCD camera. The numerical calibration free laser-induced breakdown spectroscopy algorithm included the fast deconvolution of instrumental function, and the correction of self-absorption effects. The oxide concentration C_CF calculated from calibration free laser-induced breakdown spectroscopy results and the nominal concentration C_N were very close for all samples investigated. The relative error in concentration, |C_CF–C_N|/C_N, was < 10%, < 20%, and < 5% for Fe₂O₃, MgO, and CaO, respectively. The results indicate that this method can be employed for the analysis of major elements in multi-component technical materials.     

Archaeometric Analysis of Ancient Copper Artefacts by Laser-Induced Breakdown Spectroscopy Technique

Twelve archaeological copper objects from the burial site of “Fontino” cave, near Grosseto, (around 2500–2000 B.C.) were analysed using laser-induced breakdown spectroscopy. Qualitative results and a preliminary study of the samples’ composition are reported and used to make a quantitative estimate; based on these results, the samples were classified using principal components statistical analysis. The perspectives of using laser-induced breakdown spectroscopy for archaeometric analysis are also discussed.     

Determination of Trace Elements in Dendrobium Officinale Cultivated in Various Conditions

Dendrobium officinale is an important medicinal plant in traditional Chinese medicine. The consumption of D. officinale has increased rapidly in recent years due to the health awareness among Chinese people. The present study aimed to determine trace elements levels in 42 D. officinale samples and to utilize the elemental data for identifying the cultivation technique. Eighteen trace elements (B, V, Cr, As, Mn, Fe, Mo, Cu, Zn, Se, Sr, Sn, Ti, Al, Co, As Pb, Cd, and Bi) were determined by inductively coupled plasma–mass spectrometry. Of the 11 essential elements, the mean concentrations ranged from 30.6?µg?kg^?1 (Mo) in D. officinale with greenhouse cultivation to 161?mg?kg^?1 (Fe) in D. officinale with rock cultivation, and the contributions of Mn may exceed the dietary reference intake value by the uptake of 20?g of D. officinale. Of the seven toxic elements, the mean concentrations ranged from 3.29?µg?kg^?1 (Bi) in the D. officinale with greenhouse cultivation to 342?mg?kg^?1 (Al) in the D. officinale with rock cultivation, and the contributions of Al may exceed the provisional tolerable daily intake value by the uptake of 20?g of D. officinale. The concentrations of seven metals (Bi, Pb, Fe, Al, Cr, As, and Mo) were utilized to identify the cultivation technique of the analyzed D. officinale samples through linear discriminant analysis.     

Screen-printed electrodes incorporated in a flow system for the decentralized monitoring of lead,cadmium and copper in natural and wastewater samples

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025?M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8?µg?L^?1, 4.1?µg?L^?1, and 7.5?µg?L^?1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples.     

Platinum group metals bulk analysis in automobile catalyst recycling material by laser-induced breakdown spectroscopy

Development and application of an in-situ applicable method to provide rapid determination of platinum group metals (platinum, palladium, and rhodium) elemental concentration in automobile catalyst scrap is reported. Application is based on laser-induced breakdown spectroscopy (LIBS). Actual automobile catalyst slurry in powder form was used to develop the application. With a method requiring approximately 1.5 min of examination per sample, calibration curves are presented with linear regression coefficients close to 0.99 and stability better than 3.0%.     

丝印电极法体外筛选黄嘌呤氧化酶抑制剂方法研究

建立丝印电极快速筛选黄嘌呤氧化酶(XO)抑制剂的新方法. 利用丝网印刷技术制作一次性使用的丝印碳糊电极, 采用吸附法将羧基化的多壁碳纳米管(MWNTs)修饰在电极表面, 建立测定尿酸(UA)的简单快捷的计时电流分析方法, 将该法应用于XO抑制剂的体外筛选. 在0.3 V (vs. Ag/AgCl)的工作电位下, UA在MWNTs修饰的丝印电极上产生灵敏的响应电流, 响应时间30 s, 测定UA的线性范围为2～300 μmol•L^－1, 线性方程为Y (μmol•L^－1)＝43.8240X (μA)－0.1592, r＝0.9998, 最低检出限为1 μmol•L^－1. 用该法对4种中药水提物进行了筛选, 相对空白对照组, 桑寄生500 μg•mL^－1浓度组有显著性差异. 该法简单、快速, 电极制作成本低, 所需仪器简单, 适用于体外大量筛选XO抑制剂.     

The effect of sequential dual-gas testing on laser-induced breakdown spectroscopy-based discrimination: Application to brass samples and bacterial strains

Four Cu–Zn brass alloys with different stoichiometries and compositions have been analyzed by laser-induced breakdown spectroscopy (LIBS) using nanosecond laser pulses. The intensities of 15 emission lines of copper, zinc, lead, carbon, and aluminum (as well as the environmental contaminants sodium and calcium) were normalized and analyzed with a discriminant function analysis (DFA) to rapidly categorize the samples by alloy. The alloys were tested sequentially in two different noble gases (argon and helium) to enhance discrimination between them. When emission intensities from samples tested sequentially in both gases were combined to form a single 30-spectral line “fingerprint” of the alloy, an overall 100% correct identification was achieved. This was a modest improvement over using emission intensities acquired in argon gas alone. A similar study was performed to demonstrate an enhanced discrimination between two strains of Escherichia coli (a Gram-negative bacterium) and a Gram-positive bacterium. When emission intensities from bacteria sequentially ablated in two different gas environments were combined, the DFA achieved a 100% categorization accuracy. This result showed the benefit of sequentially testing highly similar samples in two different ambient gases to enhance discrimination between the samples.     

Assessment of heavy metals,fungicide quintozene and its hazardous impurity residues in medical Panax notoginseng (Burk) F.H.Chen root

A quick, easy, cheap, effective, rugged, and safe extraction approach and gas chromatography/tandem mass spectrometry with programmed temperature vaporization sampling technology were used to determine fungicide quintozene and its hazardous impurity hexachlorobenzene (HCB) in Panax notoginseng root, which is commonly used as a rare traditional Chinese medicine worldwide. The mean recoveries were in the ranges of 94–125 and 84–119% for quintozene and HCB with relative standard deviations of 6.2–16.1% at three concentrations: 0.01, 0.1 and 1 mg kg^?1. Heavy metals arsenic, cadmium, copper and lead were simultaneously detected by an inductively coupled plasma–mass spectrometry approach after digestion with nitric acid. The above methods were used to analyze 50 samples of P. notoginseng roots collected at markets and planting bases from the special local producing areas, namely, Honghe, Kunming and Wenshan in Yunnan province, China. Quintozene and HCB in root samples were determined at <0.0015–1.50 and <0.0015–0.125 mg kg^?1. In the 50 samples, 28, 16, 56, 6 and 2% exceeded the maximum permissible levels in medicinal plants (WM/T2‐2004) for quintozene, arsenic, cadmium, lead and copper. [Correction added on 28 January 2019, after first online publication: the percentages in the preceding sentence have been corrected]. The results showed that the method is robust and suitable for measuring quintozene, its hazardous impurity and heavy metals in P. notoginseng roots.     

Laser-induced breakdown spectroscopy for branching ratio and atomic lifetime measurements in singly-ionized neodymium and gallium

Precision laboratory astrophysics measurements can be made in laser-induced plasmas created for laser-induced breakdown spectroscopy. Branching ratios from highly-energetic levels in singly-ionized neodymium may be measured by observing spontaneous emission in laser-induced plasmas in an argon environment at decreased pressures (~ 7.7 mbar). Utilizing a broadband Èchelle spectrometer with a spectral range from 200–840 nm, the spontaneous emission intensities from hundreds of transitions originating in 138 energy levels in Nd I, Nd II, and Nd III have been observed simultaneously, allowing the determination of branching ratios for these energy levels for branches greater than 1% in the visible wavelength range. In this study, eight branching ratios from the 23,229.991 cm^− 1 level in Nd II were measured and compared to previously determined values as a method for optimizing experimental conditions such as buffer gas pressure and observation delay time. The branching ratios of the eight branches were found to be in excellent agreement with three previously determined values from both experiment and theory. A plan to utilize this laser-induced plasma apparatus to measure the lifetime of the 4s5p³P₂ level at 118,727.89 cm^− 1 in singly-ionized gallium using a cascade-photon-coincidence method is also presented. Utilizing a solid Ga target ablated in a helium environment, “start photons” at 541.6 nm from a transition into the 4s5p³P₂ level and “stop photons” at 633.4 nm from a transition out of that Ga II energy level were observed. Single-photon detection will be accomplished using avalanche photodiodes with narrowband interference filters and delay times between the detection of coincident photons from these two transitions will be measured.     

痕量铜的流动注射-固相萃取-光度法测定

根据在酸性介质中,Cu²⁺对溴酸钾氧化藏红T的反应具有催化作用,利用自制的二苯卡巴腙功能键合硅胶做固相萃取固定相,联用流动注射样品处理技术,建立了在线选择性固相萃取催化动力学流动注射光度法测定痕量Cu²⁺的新方法。 研究了富集时间、反应管长、富集和洗脱流速、反应介质及洗脱液、试剂浓度、反应温度和共存物质的影响。 在最佳实验条件下,对铜测定的线性范围为0.0010~0.60 mg/L,检出限为7.9×10^-4 mg/L。 在线分离富集后分析方法的灵敏度提高20多倍,允许干扰物质存在的倍率提高了近10倍。 11次重复测定的相对标准偏差小于2.6%。 一份样品溶液从分离富集处理到测定,仅需6 min和6 mL试剂。 方法已用于中药和茶叶中痕量铜的测定。     

Microwave-Assisted Extraction and High-Performance Liquid Chromatography for Simultaneous Determination of Osthole and Isoimperatorin in Libanotis buethorimensis

Osthole and isoimperatorin are two of the major bioactive components in Libanotis buethorimensis, an effective traditional Chinese medicine. A method of microwave-assisted extraction followed by high performance liquid chromatography was developed for simultaneous determination of osthole and isoimperatorin in Libanotis buethorimensis. The conditions for extraction were formulated by using the response surface method, and the chromatographic condition was optimized. The calibration curves were linear from 10.0 to 800.0 μg mL^?1 for osthole and from 1.0 to 200.0 μg mL^?1 for isoimperatorin. Results showed that the proposed method is reliable and a potential tool for the quality assessment of Libanotis buethorimensis materials.     

Covalent bonding of homochiral metal‐organic framework in capillaries for stereoisomer separation by capillary electrochromatography

In this work, a [Cu(mal)(bpy)]?H₂O (mal, l ‐(?)‐malic acid; bpy, 4,4′‐bipyridyl) homochiral metal‐organic frameworks (MOFs) was synthesized and used for modifying the inner walls of capillary columns by utilizing amido bonds to form covalent links between the MOFs particles and capillary inner wall. The synthesized [Cu(mal)(bpy)]?H₂O and MOFs‐modified capillary column were characterized by X‐ray diffraction, thermogravimetric analysis, particle size distribution analysis, nitrogen absorption characterization, FTIR spectroscopy, SEM, and energy‐dispersive X‐ray spectroscopy (EDX). The MOFs‐modified capillary column was used for the stereoisomer separation of some drugs. The LODs and LOQs of six analytes were 0.1 and 0.25 μg/mL, respectively. The linear range was 0.25–250 μg/mL for ephedrine, 0.25–250 μg/mL for pseudoephedrine, 0.25–180 μg/mL for d ‐penicillamine, 0.25–120 μg/mL for l ‐penicillamine, 0.25–180 μg/mL for d ‐phenylalanine, and 0.25–160 μg/mL for l ‐phenylalanine, all with R² > 0.999. Finally, the MOFs‐modified capillary column was applied for the analysis of active ingredients in a real sample of the traditional Chinese medicine ephedra.