Cathode Glow Discharge-atomic Emission Spectrometry Research Articles

Elemental Analysis of Environmental Waters by Solution Cathode Glow Discharge—Atomic Emission Spectrometry (SCGD-AES) with a Multifunctional Injection System

A multifunction sample injection system combined with solution cathode glow discharge—atomic emission spectrometry (SCGD-AES) was developed based on several simple devices (six-way valve, peristaltic pump and medical injector). The equipment enables two analytical modes (continuous flow and flow injection), selected according to the sample. Moreover, the equipment can be operated at atmospheric pressure without any inert gas. Under the optimal experimental conditions (1150 V discharge voltage, 2.5 mm discharge gap, 2.32 mL min−1 flow rate and solution pH 1.0), ten elements (Na, K, Mg, Cu, Rb, Ag, Tl, Cd, Zn, and Mn) were determined using SCGD-AES in the continuous flow and flow injection modes. The detection limits for metals were from 0.1 to 264 µg L−1 (continuous flow mode) and 0.9 to 282 µg L−1 (flow injection mode). The relative standard deviations of the spectral intensities were below 2%. The instrumentation was successfully applied to the Yangtze River and reservoir water samples. The accuracy and viability were confirmed by comparison with inductively coupled plasma—atomic emission spectrometry (ICP-AES) measurements.

Sensitivity improvement of solution cathode glow discharge-atomic emission spectrometry by using refrigerating anodes for optical determination of metal elements

Sensitivity and stability improvement by reducing the metal anode temperature for metal element detection using SCGD-AES.

Spatially Resolved Characteristics of Solution Cathode Glow Discharge Source Coupled with an Interference Filter Wheel as Spectral Discrimination Device

Solution cathode glow discharge-atomic emission spectrometry (SCGD-AES) has attracted wide attention globally in recent years. The technology has the advantages of on-line detection of various metal elements, small volume, and convenience. In this work, the original spectrometer based on SCGD-AES technology was replaced by filter-wheel, photomultiplier tube (PMT) and picoammeter, which was named FPP spectral discrimination device. Analytical performance of the device with narrow-band monochromator (0.08 nm) was compared to its performance with wide-bandpass filters (10 nm) with optimized spatial. The relative standard deviation of SCGD-FPP for Na, K, Ca, Li, Sr, Rb, and Cs ranged from 0.2 to 0.8%, comparable to the 0.6 to 1.4% with the monochromator. With optimized spatial resolution, the detection limits ranged from 0.15 to 350 μg/L, and the optimal plasma spectral collected points of Na, K, Ca, Li, Sr, Rb, and Cs at 0.8 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0.6 mm, and 0.6 mm, respectively. The deviation analysis of the samples containing Na, K, Ca, and Li were analyzed under optimal conditions. The results show that a SCGD-FPP source with spatial resolution improved the detection performance.

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.

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.

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.

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.

Determination of trace heavy metals in environmental and biological samples by solution cathode glow discharge-atomic emission spectrometry and addition of ionic surfactants for improved sensitivity

Solution cathode glow discharge-atomic emission spectrometry (SCGD-AES) was evaluated for its ability to determine toxic heavy metals, including cadmium (Cd), mercury (Hg), lead (Pb), and chromium (Cr), in environmental and biological samples. A significant enhancement in heavy metal signal was observed by addition of a small amount of cetyltrimethylammoniumchloride (CTAC, C16H33 (CH3)3NCl) to the samples. The net intensity of atomic emission lines of Cd, Hg, Pb, and Cr increased by 2.1-, 4.8-, 6.6-, and 2.6-fold, respectively, after addition of 0.15% CTAC to the test solutions. The effects of ionic surfactants (CTAC) compared with non-ionic surfactants, e.g., Triton x-45 and Triton x-100, on the sensitivity of Cd, Hg, Pb, and Cr were also investigated in the present study. The enhancement effect is in the order Triton x-45<Triton x-100<CTAC for Hg, Pb and Cr and Triton x-45<CTAC<Triton x-100 for Cd. Addition of CTAC to the electrolyte solutions decreased the background intensity and fluctuation of atomic emission lines of studied metals. It also changed the surface tension and the viscosity, and increased average discharge current of electrolyte solution. SCGD sensitivity to the heavy metals greatly improved by addition of the surfactant. The improved detection limits of Cd, Hg, Pb, and Cr were 1.0, 7.0, 2.0, and 42 ng mL(-1), respectively. The proposed method was validated by quantifying Cd, Hg, Pb, and Cr in certified reference materials, including human hair (GBW 09101b) and stream sediment (GBW 07310 and GBW07311). Measurement results obtained for the determination of Cd, Hg, Pb, and Cr in the reference materials agreed well with reference values. This study improves the application of SCGD-AES in quantifying very low levels of Cd, Hg, Pb, and Cr from biological and environmental materials.

Determination of Silicate by Hollow Cathode Glow Discharge-Atomic Emission Spectrometry with Hydride Generation Technique

Abstract Hollow cathode glow discharge atomic emission spectrometry has been applied to the determination of silicon coupled with a novel gaseous hydride generation technique, involving drying of an aqueous solution of silicate (sample) and mixing with powdered LiAlH4. Sample introduction into the glow discharge chamber was performed via a pinhole at the center of the cathode which was connected to the hydride generator. The detection limit for silicon was 6μg at 288.1 nm and 30 μg at 251.6 nm. ∗ on leave from Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, 739, Japan