Glow Discharge Atomic Emission Spectrometry Research Articles

Ultratrace Pb determination in seawater by solution-cathode glow discharge-atomic emission spectrometry coupled with hydride generation

A novel method for the determination of ultratrace Pb in seawater by solution-cathode glow discharge atomic emission spectrometry (SCGD-AES) coupled with hydride generation (HG) has been developed. In the SCGD process, the hollow Ti tube, which can introduce gas instead of a solid tungsten rod is used as a discharge anode and combined with hydride generator. HG technology can not only separate Pb from a seawater matrix and reduce the matrix interference on detection, but can also significantly improve the transfer and atomization efficiencies for SCGD-AES. The optimum working conditions for HG and SCGD-AES for quantitative analysis of Pb were determined as 1% H2C2O4 as the masking agent and addition of 3% formic acid to increase Pb volatilization. The limit of detection (LOD) for Pb was decreased by two orders of magnitude in comparison to the SCGD-AES process alone. Under optimal conditions, the LOD for Pb was 0.17 μg L−1, and the relative standard deviation was 2.1% (n = 11) for 100 μg L−1 Pb in artificial seawater. The proposed quantification method was verified using a seawater reference material (BWQ7001-2016), and the obtained results agreed well with certified values. Finally, the approach was used to quantitatively analyse Pb in seawater, and the results agreed well with those obtained by inductively coupled plasma mass spectrometry. The recoveries of standard addition were between 96.0% and 103.0%.

Determination of antimony in water samples by hydride generation coupled with atmospheric pressure glow discharge atomic emission spectrometry

A low power (∼10 W), miniaturized atmospheric pressure glow discharge (APGD) source was coupled with a hydride generation (HG) system for sensitive determination of antimony in water samples with atomic emission spectrometry (AES).

Analytical Characterization of a Solution Cathode Glow Discharge with an Interference Filter Wheel for Spectral Discrimination

ABSTRACTSolution cathode glow discharge–atomic emission spectrometry (SCGD–AES) has attracted increasing attention in recent years in water and environmental analysis. In this article, the traditional spectrometer was replaced by an interference filter wheel for spectral discrimination using SCGD–AES. The aforementioned interference filters selected the spectral lines of Na, K, Ca, Li, Sr, Rb, and Cs. These spectral signals were transferred to weak currents using a photomultiplier tube and amplified by a picoammeter. The solution flow rate, discharge current and slit width were optimized individually. The analytical performance of SCGD coupled with an interference filter wheel was studied for atomic emission (SCGD–IFW–AES). The results show that the limits of detection for Na, K, Ca, Li, Sr, Rb, and Cs were 0.16, 0.36, 107, 0.53, 330, 1.93, and 13.58 µg/L, respectively. The relative standard deviations of the spectral intensities for the seven elements were 0.58, 0.94, 0.69, 0.70, 0.63, 0.67, and 0.65%, which indicated that the system operated stably. Matrix effect experiments were performed to study the effect of different concentrations of Na on the spectral intensities of K and Ca. Based on these measurements, the concentration of K in physiological saline was determined to be 0.534 mg/L by SCGD–IFW–AES.

Evaluation of analytical performance for the simultaneous detection of trace Cu, Co and Ni by using liquid cathode glow discharge-atomic emission spectrometry

In this paper, a novel liquid cathode glow discharge (LCGD) was established as a micro-plasma excitation source of atomic emission spectrometry (AES) for simultaneous detection of trace Cu, Co and Ni in aqueous solution. In order to evaluate the analytical performance, the operating parameters such as discharge voltage, supporting electrolyte, solution pH and flow rate were thoroughly investigated. The results showed that the optimal conditions are 640 V discharge voltage, pH = 1 HNO3 as supporting electrolyte and 4.5 mL min−1 flow rate. The R2 of Cu, Co and Ni are 0.9977, 0.9991 and 0.9977, respectively. The relative standard deviation (RSD) is 1.4% for Cu, 3.2% for Co and 0.8% for Ni. Under this condition, the power of LCGD is below 55 W and the plasma is quite stable. The limits of detections (LODs) for Cu, Co and Ni are 0.380, 0.080, and 0.740 mg L−1, respectively, which are basically consistent with the closed-type electrolyte cathode atmospheric glow discharge (ELCAD). Compared with ICP-AES, the LCGD-AES has small size, low power consumption, no inert gas requirement and low cost in set-up. It may be developed as a portable instrument for in-site and real-time monitoring of metals in solution samples with further improvement.

The Film Forming Mechanism of Chromium-free Passivation in the Tannic Acid System for Electrogalvanized Coating

In this paper, tannic acid, fluorine titanate and silane coupling agent passivation solution were used to prepare hot dip 55% Al-Zn steel sheet passivation coating. And then the mechanism of film formation was studied. The microstructure, surface composition, layer by layer element distribution and molecular structure of 55% Al-Zn steel sheet passivation coating were revealed in scanning electron microscopy, X ray photoelectron spectroscopy, glow discharge atomic emission spectrometry and infrared spectrometry, respectively. The results show that: in one hand, using the silane coupling agent would generate many sol-gel particles in the passivation solution. On the other hand, tannic acid would produce spatial mesh structure. Therefore, passivation solution would generate a smooth, uniform and compact 55% Al-Zn steel sheet passivation coating or membrane.

Comparative study of magnesium and calcium in Codonopsis pilosula samples detected by CF-LIBS and LCGD-AES

Emission spectra of Codonopsis pilosula samples from nine habitats were measured using calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES). Based on the measured spectra, the elements in the samples and the corresponding compositions were determined, and the results were compared with those from inductively coupled plasma mass spectrometry (ICP-MS) by using the Mg/Ca ratios. In addition, an estimation of the plasma parameters was considered and the stability of the results from both analytical methods was discussed.

Flow Injection Photochemical Vapor Generation Coupled with Miniaturized Solution-Cathode Glow Discharge Atomic Emission Spectrometry for Determination and Speciation Analysis of Mercury.

A novel, compact, and green method was developed for the determination and speciation analysis of mercury, based on flow injection photochemical vapor generation (PVG) coupled with miniaturized solution cathode glow discharge-atomic emission spectroscopy (SCGD-AES). The SCGD was generated between a miniature hollow titanium tube and a solution emerging from a glass capillary. Cold mercury vapor (Hg(0)) was generated by PVG and subsequently delivered to the SCGD for excitation, and finally the emission signals were recorded by a miniaturized spectrograph. The detection limits (DLs) of Hg(II) and methylmercury (MeHg) were both determined to be 0.2 μg L-1. Moreover, mercury speciation analysis could also be performed by using different wavelengths and powers from the UV lamp and irradiation times. Both Hg(II) and MeHg can be converted to Hg(0) for the determination of total mercury (T-Hg) with 8 W/254 nm UV lamp and 60 s irradiation time; while only Hg(II) can be reduced to Hg(0) and determined selectively with 4 W/365 nm UV lamp and 20 s irradiation time. Then, the concentration of MeHg can be calculated by subtracting the Hg(II) from the T-Hg. Because of its similar sensitivity and DL at 8 W/254 nm, the simpler and less toxic Hg(II) was used successfully as a primary standard for the quantification of T-Hg. The novel PVG-SCGD-AES system provides not only a 365-fold improvement in the DL for Hg(II) but also a nonchromatographic method for the speciation analysis of mercury. After validating its accuracy, this method was successfully used for mercury speciation analysis of water and biological samples.

Determination of calcium and zinc in gluconates oral solution and blood samples by liquid cathode glow discharge-atomic emission spectrometry

A novel flowing liquid cathode glow discharge (LCGD) was developed as an excitation source of the atomic emission spectrometry (AES) for the determination of Ca and Zn in digested calcium and zinc gluconates oral solution and blood samples, in which the glow discharge is produced between the electrolyte (as cathode) overflowing from a quartz capillary and the needle-like Pt anode. The electron temperature and electron density of LCGD were calculated at different discharge voltages. The discharge stability and parameters affecting the LCGD were investigated in detail. In addition, the measured results of real samples using LCGD-AES were verified by ICP-AES. The results showed that the optimized analytical conditions are pH = 1 HNO3 as supporting electrolyte, 4.5mLmin–1 solution flow rate. The power consumption of LCGD is 43.5–66.0W. The R2 and the RSD ranged from 630 to 680V are 0.9942–0.9995 and 0.49%–2.43%, respectively. The limits of detections (LODs) for Zn and Ca are 0.014–0.033 and 0.011–0.097mgL–1, respectively, which are in good agreement with the closed-type electrolyte cathode atmospheric glow discharge (ELCAD). The obtained results of Ca and Zn in real samples by LCGD-AES are basically consistent with the ICP-AES and reference value. The results suggested that LCGD-AES can provide an alternative analytical method for the detection of metal elements in biological and medical samples.

Analysis of metal elements by solution cathode glow discharge-atomic emission spectrometry with a modified pulsation damper

Solution-cathode glow discharge-atomic emission spectrometry (SCGD-AES) with a portable spectrometer was used to detect metal elements in solution.

Ultra-sensitive determination of inorganic arsenic valence by solution cathode glow discharge-atomic emission spectrometry coupled with hydride generation

A simple and ultra-sensitive method based on HG-SCGD-AES was developed for determination inorganic arsenic valence.

Evaluation of liquid cathode glow discharge-atomic emission spectrometry for determination of copper and lead in ores samples

In this study, a liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES) was constructed for simultaneously determination of Cu and Pb in digested ores samples, in which the glow discharge was produced between the needle-like Pt anode and electrolyte overflowing from quartz capillary. The stability of LCGD and the effects of discharge voltage, capillary diameter and flow rate on emission intensity were systematically investigated. The limits of detections (LODs) of Cu and Pb were compared with those measured by closed-type electrolyte cathode discharge-atomic emission spectrometry (ELCAD-AES). In addition, the measured results of LCGD were verified by ICP-AES. The results showed that the optimization analytical conditions were 675V discharge voltage, 1.0mm capillary diameter and 5.5mLmin−1 flow rate. The analytical response curves had good linearity in the range of 1–10mgL−1. The RSD was 2.05% for Cu and 1.27% for Pb. The LODs of Cu and Pb were 0.36 and 0.20mgL−1, respectively, which are in agreement with the closed-type ELCAD. The obtained results of Cu and Pb in ore samples by LCGD are consistent with the reference materials of ICP. The recovery of samples is ranged from 85.2–105.6%, suggesting that the determinated results have high accuracy. All the results indicated that the LCGD can provide an alternative analytical method for the determination of metal elements in ores samples.

Ultratrace Determination of Tin, Germanium, and Selenium by Hydride Generation Coupled with a Novel Solution-Cathode Glow Discharge-Atomic Emission Spectrometry Method.

We herein describe a novel method of hydride generation (HG) coupled to a newly designed atmospheric pressure solution-cathode glow discharge (SCGD) spectrometric technique for the ultratrace determination of tin, germanium, and selenium. In this novel SCGD process, gas introduction was permitted using a hollow titanium tube as both the anode and sampling port. In these experiments, the analytes were converted into volatile hydrides upon passing through the hydride generator, and were introduced into the near-anode region of the SCGD system, where they were detected directly by atomic emission spectrometry (AES). A significant improvement in both selectivity and sensitivity was achieved, which was reflected in an improvement in the detection limits (DLs) by 3 orders of magnitude, in addition to successful valence analysis of Se without the requirement for chromatographic separation. In the absence of a strict sample pretreatment process and with a reduction in electrolyte consumption, the detection limits of Sn, Ge, and Se were determined to be 0.8, 0.5, and 0.2 μg·L-1. Moreover, our HG-SCGD-AES system demonstrated excellent repeatability (<3% peak height relative standard deviation) and more than 2 orders of linear dynamic range. The optimal operating conditions are outlined herein, and the analytical performance of the system is evaluated as described. Furthermore, our method was applied for the analysis of Sn, Ge, and Se in both environmental and biological samples, and the obtained results were in good agreement with reference values.

Elemental Analysis of Mineral Water by Solution-Cathode Glow Discharge–Atomic Emission Spectrometry

ABSTRACTA solution-cathode glow discharge was used for atomic emission spectrometry. The acidic reagent, discharge current, and flow rate were optimized. The detection limits for sodium, potassium, calcium, and magnesium were 1.51, 4.13, 131, and 54.9 µg L−1, respectively. The relative standard deviation for five replicates was from 0.52 to 3.00%. Sodium, potassium, calcium, and magnesium were determined in mineral water by solution-cathode glow discharge–atomic emission spectrometry. The results demonstrate that the protocol is suitable for the elemental analysis of mineral water.

On-line separation and pre-concentration on a mesoporous silica-grafted graphene oxide adsorbent coupled with solution cathode glow discharge-atomic emission spectrometry for the determination of lead

A method has been developed to improve the sensitivity of the solution-cathode glow discharge-atomic emission spectrometry (SCGD-AES) for lead determination by coupled with flow injection (FI) technique based on an on-line solid phase extraction (SPE) separation system. A mesoporous silica-grafted graphene oxide (GO-SBA-15) material was used as sorbent and packed it in a SPE microcolumn for its high selective adsorption capacity of Pb(II). An enrichment factor of 15 was achieved under optimized conditions, at a material usage amount of 30mg, an enrichment flow rate of 1.0mLmin−1 and an eluent of 0.15molL−1 HNO3. The detection limit (DL) of Pb(II) was calculated to be 0.91μgL−1. Compared to single SCGD-AES, the sensitivity of Pb(II) was significantly enhanced by FI-SCGD-AES technique and DL could be improved 14-fold. The linear range was 10–2000μgL−1 and the relative standard deviation of the method for eleven replicate measurements of 100μgL−1 for Pb(II) was 3.8%. The accuracy was validated using certified reference materials of GBW09101b and GBW07310. The method was applied for the determination of target ions in different environmental samples with satisfactory results.

Direct determination of Cu by liquid cathode glow discharge-atomic emission spectrometry

In this study, a novel liquid cathode glow discharge-atomic emission spectrometry was developed for the direct determination of Cu in aqueous solutions, in which the glow discharge plasma was produced in the solution between the needle-like Pt cathode and the electrolyte around it. The effects of discharge voltage, solution pH, and the ionic surfactant cetyltrimethylammonium chloride (CTAC) on emission intensities were investigated. The limit of detection (LOD) of Cu was compared with those measured by closed-type electrolyte cathode discharge-atomic emission spectrometry (ELCAD-AES). The results showed that the optimal operation conditions are voltage of 135V, a pH of 1, and addition of 0.15% CTAC. CTAC can enhance the emission intensity and lower the LOD of Cu I. The net intensity of atomic emission lines of Cu I at 324.8nm with 0.15% CTAC improved by 1.5 fold, and the LODs of the Cu at 135V with 0.15% CTAC and without CTAC are 0.019 and 0.234mgL−1, respectively. The analytical capability of Cu in this study is comparable to the closed-type ELCAD-AES, and it satisfied the recommended levels of Cu in the WHO standards for drinking-water quality. This technique can be effectively used for on-line monitoring of metal ions in aqueous samples.

Simultaneously determination of multi metal elements in water samples by liquid cathode glow discharge-atomic emission spectrometry

In this work, a liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES) was constructed for simultaneously determination of K, Na, Ca, Mg and Zn in water samples (tap water, mineral water, Yellow River water and waste water), in which the glow discharge plasma was produced between the needle-like Pt anode and electrolyte around a quartz capillary cathode. The effects of the supporting electrolyte, discharge voltage and organic additives on emission intensity were investigated in detail. The limits of detections (LODs) of metals were compared with those measured by the closed-type electrolyte-cathode discharge-atomic emission spectrometry (ELCAD-AES). In addition, the measured results of water samples using LCGD were verified by ICP. The results showed that the optimal operation conditions are pH=1 HNO3 as supporting electrolyte, addition of 0.15% formic acid and 650V discharge voltage. The R2 and the RSD are ranged from 0.9887 to 0.9990 and 1.10% to 2.19%, respectively. LODs of K, Na, Ca, Mg and Zn are 0.02, 0.04, 0.19, 0.04 and 0.05mgL−1, which are in agreement with the ELCAD-AES, and satisfied the recommended levels of the China standards for drinking water quality. The obtained results of Na, K, Ca, Mg and Zn in water samples by LCGD and ICP have certain difference. This result provides an alternative analytical method for the determination of metal elements in water samples.

Evaluation of flow injection-solution cathode glow discharge-atomic emission spectrometry for the determination of major elements in brines

A new method for the determination of major metal elements in high salinity brines was developed by solution cathode glow discharge (SCGD) with flow injection analysis (FIA). The matrix interferences of major cations and anions in brines have been evaluated. It was found that high concentration of Na+ and K+ could interfere each other, K+ at a concentration of 400mgL−1 enhanced the signal intensity of Na+ more than 20%. The effect of the anions was observed and it was noted that the signal intensity of both Ca2+ and Mg2+ were suppressed significantly when the SO42− reached 100mgL−1. It was demonstrated that some low molecular weight organic substances such as formic acid, glycerol and ascorbic acid could eliminate interference of SO42− even with volume percentages of 0.5%. Under the optimized condition, the proposed FIA-SCGD can determine K, Na, Ca and Mg with the limits of detection of 0.49 (K), 0.14 (Na), 11 (Ca) and 5.5 (Mg) ngmL−1. The proposed method has been successfully applied to the analysis of 5 salt lake samples and compared with those obtained with inductively coupled plasma atomic emission spectrometry (ICP-AES). The advantages of small size, low energy consumption, good stability and repeatability indicated that the SCGD is promising for the determination of major ions in brine samples.

Highly sensitive elemental analysis of Cd and Zn by solution anode glow discharge atomic emission spectrometry

In this study, a highly sensitive liquid electrode discharge atomic emission source was developed for the determination of Cd and Zn in aqueous solutions.

Определение толщины гальванических покрытий Ni-P, Sn-Bi и Sn-Pb методом атомно-эмиссионной спектрометрии с тлеющим разрядом постоянного тока

Glow discharge atomic emission spectrometry allows determining the chemical composition of the coatings and their thickness as well as to conduct the depth analysis. Atomic-emission determination of the coating thickness on a single calibration curve can be performed by using the sputtering rates of coatings with different chemical composition. To realize this method the set of comparative samples with Ni-P coating was made. Samples are certified for the coating thickness by a regulated chemical, metallographic and X-ray fluorescence analysis methods. Using the atomic emission spectrometer with a dc glow discharge under optimal operating parameters, which provides a flat bottom of the crater, the calibration curve for dependence of the Ni-P coating thickness against its cathode etching was obtained. It is shown that the metrological characteristics of the current method for control of Ni-P coating thickness is not worse than the methods regulated by GOST. Samples of Sn-Bi and Sn-Pb coatings were made. The thickness of the coating was determined by the regulated methods of analysis, the optimal operating parameters of the glow discharge, which provides a flat bottom of the crater, were determined, and the absolute and relative sputtering rates of coatings in dc glow discharge were measured. Using the atomic emission calibration curve for Ni-P coating and established relative rates of sputtering, the thickness of Sn-Bi and Sn-Pb coatings was determined. It is shown that the metrological characteristics of this method are not worse than the methods regulated by GOST. Methodology for measuring the thickness of Ni-P, Sn-Bi and Sn-Pb coatings using atomic emission spectrometry with a dc glow discharge was developed and certified. Key words : atomic emission spectrometry, DC glow discharge, electroplating Ni-P, Sn-Bi and Sn-Pb, sputtering rate, operating parameters of the discharge, thickness of the coating. (Russian) DOI: http://dx.doi.org/10.15826/analitika.2015.19.1.007 A.L. Chicherskaia, A.A. Pupyshev Ural Federal University named after the first President of Russia B. N. Yeltsin, Yekaterinburg, Russian Federation

Determination of Hg2+ by on-line separation and pre-concentration with atmospheric-pressure solution-cathode glow discharge atomic emission spectrometry

A simple and sensitive method to determine Hg2+ was developed by combining solution-cathode glow discharge atomic emission spectrometry (SCGD-AES) with flow injection (FI) based on on-line solid-phase extraction (SPE). We synthesized l-cysteine-modified mesoporous silica and packed it in an SPE microcolumn, which was experimentally determined to possess a good mercury adsorption capacity. An enrichment factor of 42 was achieved under optimized Hg2+ elution conditions, namely, an FI flow rate of 2.0mLmin−1 and an eluent comprised of 10% thiourea in 0.2molL−1 HNO3. The detection limit of FI–SCGD-AES was determined to be 0.75μgL−1, and the precision of the 11 replicate Hg2+ measurements was 0.86% at a concentration of 100μgL−1. The proposed method was validated by determining Hg2+ in certified reference materials such as human hair (GBW09101b) and stream sediment (GBW07310).