Microwave Plasma Torch Atomic Emission Research Articles

Gaussian process regression coupled with MPT-AES for quantitative determination of multiple elements in ginseng

A comprehensive understanding of spectral information is the most reliable approach to identify ginseng characteristics and quality. More data is produced due to the use of a high resolution spectrometer, which in turn requires high-efficiency computational capability. To well address such problems, chemometrics plays a significant part and shows satisfactory results. In this paper, a Gaussian process regression (GPR) is proposed to couple microwave plasma torch-atomic emission spectrometry (MPT-AES) for quantitative determination of multiple elements in ginseng. GPR as a probabilistic method is capable of dealing with massive data and illustrating the outputs with probabilistic meanings. With high-dimension input variables involved, the principal component analysis (PCA) is proposed to reduce computational amount and improve variable representativeness. The results show that GPR is superior to the conventional approach compared with support vector regression (SVR) by evaluation indexes. All the work is performed based on real ginseng spectral data. Taking into account the computational amount caused by large datasets of scales, three approximation methods (subset of datasets (SD), subset of regressors (SR) and projected process (PP)) are applied to address this problem, which in a way shrink the training set with a certain similar result. It is concluded that the Gaussian process performs well in spectral analysis and has the potential for further practical applications.

Sensitization for Determination of Iron by Microwave Plasma Torch Atomic Emission Spectrometry

Sensitization for Determination of Iron by Microwave Plasma Torch Atomic Emission Spectrometry

Determination of Trace Elements in Rice Flour Using Microwave Plasma Torch-Atomic Emission Spectrometry:Design and Practice of a College Chemistry Experiment of Instrumental Analysis

Determination of Trace Elements in Rice Flour Using Microwave Plasma Torch-Atomic Emission Spectrometry:Design and Practice of a College Chemistry Experiment of Instrumental Analysis

Cloud point extraction of rare earths and zinc using 1,10-phenanthroline and Triton X-114 coupled with microwave plasma torch-atomic emission spectrometry

In the present work, cloud point extraction (CPE) of rare earths and zinc coupled with microwave plasma torch-atomic emission spectrometry (MPT-AES) was studied with 1,10-phenanthroline as the chelating agent and polyethylene glycoltert-octylphenyl ether (Triton X-114) as the surfactant.

Development of particle swarm optimization–support vector regression (PSO‐SVR) coupled with microwave plasma torch–atomic emission spectrometry for quality control of ginsengs

As people have become more focused on their own health, the role of ginseng for medical uses has begun to receive substantial interest. However, the quality control of ginseng remains in question because different species vary considerably in this respect. In this paper, particle swarm optimization–support vector regression combined with microwave plasma torch–atomic emission spectrometry (MPT‐AES) was used, for the first time, for quality control of ginseng. To build calibration models, quantitative determination of target element concentrations in ginseng samples was conducted by MPT‐AES because ginseng quality was closely related to the place of origin and can thus be judged by the elemental composition. Characteristic spectral lines were extracted via principal component analysis to reduce the computational effort and improve the representativeness of the input variables. Two heuristic algorithms, particle swarm optimization and a genetic algorithm, were selected to optimize the parameters (eg, c, g, and ε) that were extremely significant in the construction of the support vector regression (SVR) models. Another linear regression approach, partial least squares regression (PLSR), was also used and compared. The comparisons were based on evaluation indexes, namely, the root mean square error and the squared correlation coefficient (R2). A significant difference between SVR and PLSR showed that SVR outperformed PLSR in such a multivariate regression problem. The acquired results showed that particle swarm optimization was slightly better than a genetic algorithm. In conclusion, the proposed MPT‐AES combined with particle swarm optimization–support vector regression is appropriate for quantitative elemental analysis and further application in the quality control of ginseng.

Support vector machine classification for determination of geographical origin of Chinese ginseng using microwave plasma torch-atomic emission spectrometry

The geographical origin of Chinese ginseng is of great concern to customers, since quality varies tremendously with geographical origin.

Polymer monolith microextraction coupled to microwave plasma torch–atomic emission spectrometry for the determination of Nd, Eu and Yb in tea samples

A reliable and rapid method based on polymer monolith microextraction (PMME) combined with microwave plasma torch-atomic emission spectrometry (MPT-AES) was established for the determination of trace rare earth elements (REEs), Nd (light), Eu (medium) and Yb (heavy). Several parameters affecting extraction efficiency, including sample pH, sample flow rate, sample volume, eluent concentration, eluent flow rate and eluent volume, were investigated and optimized in detail. Under the optimum conditions, the limits of detection (n = 7) and limits of quantification (n = 7) for Nd, Eu and Yb (based on a 0.8 mL sample volume) were determined to be 1.07, 0.83 and 1.47 μg L−1, and 3.57, 2.78 and 4.90 μg L−1, respectively. The enrichment factors for Nd, Eu and Yb (5 μg mL−1) were determined to be 15.1, 12.8 and 12.5, respectively, with relative standard deviations (n = 7) of 5.10%, 5.43% and 7.84%. The proposed method has been successfully applied to the analysis of Nd, Eu and Yb in tea samples with a recovery range of 81.2–109.2%.

Microwave plasma torch-atomic emission spectrometry for the on-line determination of rare earth elements based on flow injection preconcentration by TiO2–graphene composite

In this work, we synthesized TiO2–graphene composite as a novel preconcentration material. It was enclosed in a microcolumn in the on-line flow injection system to adsorb trace light (La), medium (Tb), and heavy (Ho) rare earth elements (REEs) prior to their determinations by microwave plasma torch-atomic emission spectrometry (MPT-AES). Various experimental parameters, such as sample loading time, sample flow rate, sample pH, eluent flow rate, eluent concentration, and interfering ions, were investigated systematically. Under the optimum conditions, the detection limits (three times of standard deviations of blank by 7 reiterations) of La, Tb, and Ho were found to be 2.2, 1.6, and 2.8μgL−1, with enrichment factors of 17.1, 11.1, and 10.2, respectively. Relative standard deviations for the determination of the target REEs were 3.6%, 1.3%, and 1.4%, respectively (n=7). The developed method was validated by the analysis of La, Tb, and Ho in certified reference material (GBW07313, marine sediment) and high purity REE oxide samples.

Chelating–Ultrafiltration Treatment of Some Heavy Metal Ions in Aqueous Solutions by Crosslinking Carboxymethyl Modified Cornstarch

Crosslinking carboxymethyl starch (CCMS) powder of degree of substitution (DS) 0.43–0.59 was prepared by the process of two steps of alkali addition synthesis. The technique of powder coupling with ultrafiltration was used to absorb Cu2+, Zn2+, Ni2+, Pb2+, and Cd2+ from aqueous solutions. FTIR was used to demonstrate the successfully grafting of carboxymethyl groups, and the technique of microwave plasma torch atomic emission spectrometer was applied in rapid determination of the aforementioned heavy metals ions. The results revealed that the removal sequence of heavy metal ions followed the order of Pb2+>Cu2+>Cd2+>Zn2+>Ni2+. By assistant of diethylene triamine penlaacetic acid, the quaternary system of Pb2+/Ni 2+/Cd2+/Cu2+ mixture solution could have the ideal separation. Besides, the influence of pH, ζ potential, DS value, and membranes molecular weight cut-off on removal of 20 mg L−1 Pb2+ or Ni2+ was also investigated.

Crosslinked Carboxymethyl Modified Starch for Treatment of Heavy Metals Water by Technique of Chelating-Ultrafiltration

Crosslinked carboxymethyl modified starch (CCMS) was prepared by chemical modification of nature cornstarch. This modified degradable polymer had turned out to be a strong ability to chelate heavy metal ions. Using the instrument of microwave plasma torch atomic emission spectrometer(MPT-AES), 20.00 mg/L of Cu, Zn, Ni, Pb, Cd were detected under the Sewage Discharge Standards requirements after adding 90, 154, 86, 70, 546mg/L of CCMS respectively. The separation of the heavy metal ions and CCMS solutions were used the technique of ultrafiltration, with a molecular weight cut-off (MWCO) of 50000. By the same treatment, the chelating sequence of the heavy metals were also measured and decreased in the order of Pb>Cu>Cd>Zn>Ni.

Iodine Determination by Microwave Plasma Torch Atomic Emission Spectrometer Coupled with Online Preconcentration Vapor Generation Technique

This article focuses on iodine determination by microwave plasma torch atomic emission spectrometry (MPT-AES) coupled with online preconcentration vapor generation method. A new desolvation device, multistrand Nafion dryer, was used as the substitute for condenser desolvation system. Some experimental conditions, such as preconcentration time, acidity of sample solution, rinsing solution acidity and dynamic linear range were investigated and optimized. The new desolvation system eliminates the problem of decreasing emission intensity of I(I) 206.238 nm line with the increase of working time on a conventional condenser desolvation system, thus greatly improving the reproducibility.

Flow injection on-line preconcentration with an ion-exchange resin coupled with microwave plasma torch-atomic emission spectrometry for the determination of trace rare earth elements

A sensitive and rapid on-line method has been developed for the determination of trace amounts rare earth elements (REEs), lanthanum, cerium, neodymium and yttrium, by microwave plasma torch-atomic emission spectrometry (MPT-AES) combined with micro-column separation/preconcentration. A strong basic cinnamene anion exchange resin is used for matrix elimination and enrichment of the analytes. The adsorbed metal ions are subsequently eluted from the column and transferred into the detector with nitric acid solution for simultaneous multi-element determination. Various factors influencing the separation/preconcentration, sample flow rate, loading time, acidity and eluent flow rate, concentration, have been studied in detail. Under the optimized conditions, the detection limits for lanthanum, cerium, neodymium and yttrium based on three times of standard deviations of blank by 7 replicates are 0.89, 2.02, 1.56 and 0.78 μg·L − 1, and the relative standard deviations are determined as 1.54, 4.29, 4.95 and 3.90%, respectively. The proposed method has been applied to the analysis of the four REEs in high purity Sm 2O 3, Eu 2O 3, Gd 2O 3, Tb 2O 3, Dy 2O 3, Yb 2O 3, and Lu 2O 3 samples with a recovery range of 95.1–104.8%.

Coupling on-line preconcentration by ion-exchange with microwave plasma torch-atomic emission spectrometry for the determination of cobalt and nickel

In the present work, a simple and sensitive preconcentration-microwave plasma torch-atomic emission spectrometric procedure was carried out for the determination of cobalt and nickel. The method was based upon a flow-injection system with on-line preconcentration of the metal ions on a minicolumn of a strong acid cation-exchange resin. The operation parameters including sample acidity, flow rate, loading time, and eluent concentration, flow rate were studied and optimized. Under the optimal experimental conditions the enrichment factors were calculated as 13.58 and 17.65 for cobalt and nickel, respectively. The relative standard deviations, 3.73% for cobalt and 4.23% for nickel ( n = 7), and a sample throughput of 40 h − 1 were obtained. Furthermore, the limits of detection were shown to be 1.28 and 1.80 μg·L − 1 for cobalt and nickel, respectively. The method was applied to the determination of cobalt and nickel in tea samples and the accuracy was assessed through recovery experiments.

Determination of Silicon, Iron, and Vanadium in Petroleum Coke by Microwave Digestion-Microwave Plasma Torch Atomic Emission Spectrometry

Using microwave plasma torch (MPT) as an excitation light source, argon as support gas, the sample solution was introduced into plasma by pneumatic nebulization system. The determination of silicon, iron, and vanadium in petroleum coke by microwave plasma torch atomic emission spectrometry (MPT-AES) was studied. The experimental conditions were optimized and chosen. The effects of coexistent ions on silicon, iron, and vanadium emission signal were investigated in detail. The detection limits for silicon, iron, and vanadium were 0.040 μg/mL, 0.022 μg/mL, and 0.052 μg/mL, respectively. Linear dynamic ranges were 0.2–6 μg/mL, 0.1–100 μg/mL, and 0.2–100 μg/mL, respectively. The addition recoveries were in the range of 95.8%–105.0%. Petroleum coke samples were digested in the sealed vessel by a microwave digestion system. The optimum parameters for microwave digestion were studied and selected. The method of microwave digestion is a useful, time-saving technique and can reduce total sample preparation time. The result shows that the method is effective in detecting silicon, iron, and vanadium in petroleum coke and has the advantages of accuracy, easy operation, high automation, and low operation cost.

Studies on injector pump-ultrasonic nebulizer feeding sample system for MPT-AES

The feeding-sample system used by microwave plasma torch atomic emission spectroscopy (MPT-AES) is the pneumatic nebulization system; its efficiency, however, is not good. A newly built injector pump-ultrasonic nebulizer combination feeding-sample system has been designed. Its performance was tested and compared with that of the pneumatic nebulization system. It can be concluded that the newly built feeding-sample system can increase the spectral line intensity by about two to three times and decrease the detection limit by about 2 to 10 times. Moreover, this newly built system can reduce the time taken washing the sample cell from 30 min or so to about 10 min.

Evaluation of Improved Ultrasonic Nebulizer for Miniature Simultaneous Microwave Plasma Torch Spectrometer

A new automatic sample solution introduction system for miniature simultaneous microwave plasma torch(MPT) atomic emission spectrometer was developed. The operating parameters were optimized. The detection limits of the spectrometer with an ultrasonic nebulizer for Ag, Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Sr, and V are 5—10 times lower than those obtained with a pneumatic nebulizer and are also lower than those obtained by a Model JX-1010 MPT spectrometer. Two practical samples were analyzed to test the reliability and sensitivity of the system.

Development of a miniature simultaneous MPT spectrometer

An unique miniature simultaneous microwave plasma torch (MPT) atomic emission spectrometer employing linear UV intensified charge-coupled device (ICCD) array detector has been developed and studied preliminarily. The detection limits and precisions of the spectrometer for Ag, Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Sr and V by using different CCD exposure times have been determined. An analysis of a practical sample has been carried out. The preliminary results demonstrate that such simultaneous spectrometer has advantages of saving sample and time, especially suitable for use as detector for chromatography and in combination with flow injection systems. Taking analytical figures of merit and portability into accounts, the miniature simultaneous MPT system will have extended application areas and greater competition potential as compared with commercialized scanning MPT spectrometers.

A simple flow-injection on-line clean-up system for microwave plasma-torch atomic emission spectrometry.

A simple flow injection (FI) on-line clean-up system has been developed for microwave plasma-torch atomic emission spectrometry (MPT-AES). A non-selective strongly acidic cation-exchange resin was used to achieve the goal of "on-line clean-up". Ag and Zr, which form halogen-complex anions in halide acid media, and Cr, Mo, and P, which exist as acid group anions or acids (neutral) in acidic solution, were determined and the interfering matrix cations were removed on-line. Satisfactory analytical results were obtained from some practical samples by use of this procedure.

Determination of arsenic by continuous hydride generation with direct introduction into an O 2 -argon microwave plasma torch atomic emission spectrometer

The determination of arsenic was studied with a simple and economic method. A continuous hydride generation system is interfaced to a microwave plasma torch atomic emission spectrometer (MPT-AES). Arsenic hydride is transferred directly and continuously by the carrier gas into the plasma torch without separation of hydrogen. When oxygen is introduced into the outer tube of the plasma torch, the plasma is more stable and has a higher tolerance to hydrogen. The detection limit (3σ) is 5.2 μg/L when the forward power is 100 W with argon as support gas. Application to the standard sample coal fly ash showed a comparable result to the certified quantity.

Studies on end-on-viewed microwave plasma torch atomic emission spectrometry

In this paper, end-on-viewed microwave plasma torch (MPT) atomic emission spectrometry (AES) was studied in detail. In addition, by using the same experimental setup, a comparison of the analytical performance of the end-on-viewed MPT-AES system with that of the traditional side-on-viewed MPT-AES was made. A cut-off gas was adopted which was passed between the MPT and the lens to prevent the analyte from depositing on the lens and the heated gas from damaging the optical system. The effects of the operating parameters, such as carrier gas flow rate, support gas flow rate, microwave forward power and the temperature of the spray chamber in either system, were evaluated and compared. It was found that the optimal operating parameters for different elements were almost the same with the end-on-viewed MPT, while those with the side-on-viewed MPT were quite different. The end-on-viewed MPT was suitable for simultaneous multielement analysis without the need to compromise the operating conditions, which was, however, necessary for the side-on-viewed MPT. The analytical performance for twelve elements was also compared. The results indicated that the advantages of the end-on-viewed MPT include improved sensitivity and lowered detection limits and matrix effects as compared with the side-on-viewed MPT. The average improvement factor in the detection limits was found to be in the range of 3–10, the best being about 23. The narrower dynamic linear range caused by the hot tail of the plasma was a disadvantage.