Microwave Plasma Torch Atomic Emission Spectrometry 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.

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.

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

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.

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.

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 trace Ag, Au, Ge, Pb, Sn and Te by microwave plasma torch atomic emission spectrometry coupled with an electrothermal vaporization sample introduction system

An electrothermal vaporization (ETV) sample introduction device tantalum filament was combined with microwave plasma torch atomic emission spectrometry (MPT-AES) for determination of several trace elements. Some operating parameters of the system were optimized. The effects of easily ionized elements (EIEs) on the emission intensities of the tested elements were studied in detail. It was revealed that there was no interference resulting from small amount of sample matrix; while with the existence of large amount of sample matrix, the method of standard addition could be used to determine trace elements in samples. So, no modifier was required in this method. The results indicated that ETV-MPT-AES not only has the advantage of micro sample consumption (a volume of 3 μl for each injection), but also offers high sensitivities for the determination of Ag, Au, Ge, Pb, Sn and Te as compared with those obtained with pneumatic nebulization (PN) MPT-AES.

On-line preconcentration with activated carbon for microwave plasma torch atomic emission spectrometry

This paper presents a method whereby trace elements are adsorbed in NH 4ClNH 3 medium on activated carbon and then determined by microwave plasma torch atomic emission spectrometry (MPT-AES). The working conditions (including microwave forward power, gas flow rate, NH 3NH 4Cl concentration in the sample solution, HCl concentration in the eluant, sample introduction rate and preconcentration time) were investigated in detail. The effects of concomitant ions were studied. The experimental results for such analytes as Pb, Mn, Cd, Cu and Fe indicate that the procedure can eliminate fundamentally the interferences caused by alkali and alkaline earth metal elements and the application of it to the determination of iron in industrial silicon and tap water samples is successful.

Use of microwave plasma torch atomic emission spectrometry for the determination of silicon

A method for the elimination of matrix effects was developed for the determination of trace amounts of silicon by microwave plasma torch atomic emission spectrometry (MPT-AES). The sample solution was introduced into the MPT with a pneumatic nebulizer (PN). When Ar was used as both carrier and support gas, a detection limit of 10.8 ng/ml was obtained. The precision was 4.2% (RSD). The characteristics of the emission spectrum of silicon in MPT was studied in detail. The interference of some concomitant cations with the silicon emission was eliminated by incorporation of a cation-exchange column into the flow injection system. The method has been applied to analyze some practical samples and the results obtained are satisfactory.

Flow Injection Sample Introduction into Microwave Plasma

Flow injection (FI) sample introduction was used in microwave plasma torch atomic emission spectrometry (MPT-AES). An FI in conjunction with a pneumatic nebulizer was evaluated. The effects of microwave forward power, flow rate of support gas and carrier gas, HCl concentration in sample solution, sample-loop volume, and some easily ionized elements (EIEs) on emission intensity were examined in detail. Selected elements were determined by FI-MPT-AES. The experimental results shown in this paper indicate that the effect of easily ionized elements (EIE) can be reduced and the analytical performance of MPT-AES using and FI sample introduction system is promising.

Analytical performance of the microwave plasma torch in the determination of rare-earth elements with optical emission spectrometry

A recently developed microwave discharge device called the microwave plasma torch (MPT) is used in this work to evaluate its analytical performance in the determination of rare earth elements with optical emission spectrometry. Optimization of the instrument was performed by using individual elements with emphasis on the plasma observation zone, carrier and support gas flow rates. The detection limits for 15 rare earth elements obtained by MPT atomic emission spectrometry at 70 W are in the order of ng/ml. The precision (R.S.D.%) calculated with eleven continuous measurements at a concentration of about two orders of magnitude higher than the detection limits is in the range of 2.0 (Y) to 4.9 (Tb). Some comparisons were made between inductively coupled plasma and MPT methods, and the results show that in some cases, most of the sensitivity lines observed in these two sources for rare-earth elements are not identical. Compared with the ICP emission spectrum, the MPT source gives relatively simple spectra and much lower background emission. A preliminary examination of matrix effects with varying matrix concentrations shows that some easily ionized elements give significant enhancement on analyte signal and that aluminum suppresses the signals considerably. For some other elements (Co, Ni and Zn) no remarkable matrix effects are observed at a concentration level of 10 μg/ml.