Glow Discharge Atomic Emission Research Articles

Sensitive Determination of Alkali Metals by Liquid Anode Glow Discharge-Atomic Emission Spectrometry (LAGD-AES)

Liquid anode glow discharge-atomic emission spectrometry (LAGD-AES) was employed for the determination of alkali metals in brine and bottled drinking water samples. The results demonstrated that the optimum operating conditions are a discharge voltage of 630 V, a flow rate of 2.0 mL min−1, a supporting electrolyte solution of pH 1.7 HNO3, and a discharge gap of 0.5 mm. Alkaline-earth ions (e.g., Ca2+, Mg2+, and Sr2+) and Cr3+ interfere with the determination of alkali metals. The limits of detection (LODs) for the alkali metals, namely cesium (Cs), potassium (K), lithium (Li), sodium (Na), and rubidium (Rb) are 135, 6.21, 3.15, 7.57, and 31.1 µg L−1, respectively. The relative standard deviations are less than 5%, and the power consumption is approximately 13 W. The obtained results are in good agreement with the certified standard value for Li in the certified reference material and are consistent with the values obtained by ICP-OES and reference standards for K and Na in real samples. The concentrations of the Cs and Rb are considerably below the LAGD-AES detection limit. Consequently, they can be considered negligible. The results of the spiked water analysis are broadly consistent with the spiked values, with recoveries from 82% to 112%. LAGD-AES is an excellent technique for the sensitive determination of alkali metals due to its compact design, no requirement for inert gas, and low energy consumption.

Solution Cathode Glow Discharge – Atomic Emission Spectrometry (SCGD-AES) With an Interference Filter for Spectral Discrimination for the Determination of Thallium in Surface Water

Solution cathode glow discharge atomic emission spectrometry (SCGD-AES) using wide-bandpass (10-nm) interference filters (IF) as a spectral discrimination device was used for the determination of thallium (Tl) in surface water. The use of wide-bandpass interference filters greatly reduces the cost of traditional detection instruments. The influence of solution flow rate, discharge current and pH on the detection limit was characterized. Moreover, matrix effect experiments were performed to study the effect of different concentrations of Na+, K+, Ca2+, and Mg2+ on the Tl signal intensity. Using a solution flow rate of 2.8 mL/min, a discharge current of 50 mA, and pH of 1.0 with HNO3 as the supporting electrolyte, SCGD coupled with an interference filter provided a detection limit of 7.76 μg/L for Tl in water samples, comparable to traditional SCGD-AES. Furthermore, the spiked recovery rate of Tl is quantitative in real water samples and comparable to the performance of inductive coupled plasma – optical emission spectrometry (ICP-OES).

Rapid Determination of Calcium, Iron, and Zinc in Gluconate Oral Solutions by Solution Cathode Glow Discharge – Atomic Emission Spectroscopy (SCGD-AES)

A novel solution cathode glow discharge atomic emission spectroscopy (SCGD-AES) system coupled with simplified sample preparation was developed for determining Ca, Fe, and Zn in gluconate oral solution. The preparation of the oral solution only involves diluting 1 g of the sample 100-fold and acidification with HNO3 to a concentration of 0.1 mol L−1. The preparation of each solution requires less than 5 min. Five oral solutions containing Ca, Fe, and Zn were analyzed. The results indicate that the optimal parameters are HNO3 of pH 1.0 as the electrolyte, a sample flow rate of 2.05 mL min−1, and a discharge current of 65 mA. The detection limits (DLs) of Ca, Fe, and Zn were 58.64, 64.29, and 15.92 µg L−1. The analyses by SCGD-AES for Ca, Fe, and Zn using direct dilution are in agreement with the values by ICP-OES and SCGD-AES with digestion. A t-test was conducted on the oral liquid samples, revealing that the majority of the obtained p-values exceeded .05. In addition, SCGD-AES reduces the time, energy, and quantity of concentrated HNO3 compared with previous studies, and the measurement time of each oral liquid sample was less than 2 min. These findings demonstrate the use of SCGD-AES as an expedited and dependable method for the determination of trace elements in health food products.

Ultra-sensitive determination of mercury in flue gas by atmospheric pressure glow discharge atomic emission spectrometry coupled with gold amalgam enrichment

In this work, a highly sensitive procedure for the determination of mercury in flue gas was developed, based on direct-current atmospheric pressure glow discharge in hydrogen and helium (H2-He) atomic...

Sustainable Solution Anode Glow Discharge-Atomic Emission Spectroscopy (SAGD-AES) with Semiconductor Cathode Cooling for Elemental Analysis

A long-term sustainable tungsten cathode-solution anode glow discharge (SAGD) source for atomic emission spectrometry was developed for the determination of heavy metal elements. The tungsten cathode of this source was cooled by a compact refrigeration semiconductor, which is simple in design and able to operate at atmospheric pressure for long periods. When the equipment operates at its optimal conditions (75 mA discharge current, 2.0 mm discharge gap, 3.8 mL min−1 flow rate, and solution pH value of 2.0), the detection limits of Ag (338.24 nm), Cd (228.80 nm), Hg (253.66 nm), Pb (368.28 nm), Tl (337.52 nm), and Zn (213.79 nm) were explored, and the values were 0.030, 1.7, 7.2, 17, 0.24, and 25 μg L−1, respectively. The interference of coexisting ions in water, such as K+, Ca2+, Na+, Mg2+, and Li+, on the analytical performance of the solution anode glow discharge-atomic emission spectrometry (SAGD-AES) for Cd, Hg, Pb, and Zn were investigated. The results showed that coexisting metal ions’ interferences are insignificant. The SAGD-AES system was successfully applied for analyzing water samples from the Yangtze River and Baixi River, and its accuracy and practicality were verified by comparison with inductively coupled plasma-optical emission spectrometry (ICP-OES) results.

Determination of Metals by Portable Millisecond Pulsed Solution Cathode Glow Discharge (SCGD) Atomic Emission Spectroscopy (AES)

In order to determine metal ions in aqueous solution, a millisecond pulsed solution cathode glow discharge (SCGD) source coupled with a portable spectrometer was developed for atomic emission spectrometry (AES). The millisecond pulsed SCGD source was operated with two high-voltage DC power supplies and a high-voltage pulse switch, specifically boosting the analyte excitation and sustain the glow discharge. The method to excite the plasma discharge contrasts with traditional approaches that employ a single power source. The influence of operating parameters, including pulsed voltage, pulsed frequency, duty ratio, and sample flow rate, were optimized to construct a system having good stability and improved excitation of metal ions. The optimum detection limits for Na, K, Li, Mg, Ag, Cs, Rb, and Sr were 0.17, 0.32, 0.38, 0.50, 2.65, 1.30, 0.22, and 74.02 µg·L−1, respectively. Furthermore, mountain spring, Yangtze River, and reservoir water were spiked with Ag, Rb, and Cs; the recoveries ranged from 105% to 106%, 106% to 107%, and 107% to 108% indicating that the developed system has favorable analytical performance.

Determination of Metals in Environmental Waters by Solution Cathode Glow Discharge -Atomic Emission Spectroscopy (SCGD-AES) with a Syringe Pump for Sample Introduction

This study reports a syringe injection pump for sample introduction for solution cathode glow discharge (SCGD) atomic emission spectroscopy (AES). The experimental conditions are optimized at 60 mA discharge current, 2.5 mm gap spacing, 2.0 mm distance from the glass capillary to cathode, 1.60 mL/min flow rate, and pH 1.0 based on the detection limits (DLs) obtained for Li, Cd, Cu, Ag, Mn, Pb, Cr, and Zn. The detection limits for Li, Cd, Cu, Ag, Mn, Pb, Cr, and Zn were 0.24, 12.26, 12.08, 1.09, 46.42, 25.81, 183.05, and 29.01 µg/L, respectively, significantly lower than using the traditional peristaltic pump. The detection limits decreased by 1.4, 1.8, 2.2, 5.0, 1.4, 1.4, 1.4, 1.6, and 2.2-fold for these elements. The flow rate and the solution consumed per unit time were significantly reduced using this design. The spectral detection revealed stable and practical operation of the system with relative standard deviations <0.85%. Water samples from Yangtze River, Baixi River, and Baiyun Reservoir are analyzed using the modified SCGD system and its evaluation is based upon comparison to inductively coupled plasma—optical emission spectroscopy (ICP-OES). The modified device operates at atmospheric pressure without inert gas and integrates a syringe injection pump and a compact spectrometer to optimize solution utility, analytical performance, and operation size for industrial and environmental monitoring applications.

Multi-element Simultaneous sensitization of solution cathode glow discharge atomic emission spectrometry by using portable semiconductor anode refrigeration

In this study, a modified solution cathode glow discharge atomic emission spectrometry (SCGD-AES) was used to detect metal elements in electroplating sewage. The SCGD-AES device was equipped with a portable semiconductor anode refrigeration unit, which was built independently. The red-heat effect of tungsten electrode was alleviated by adding the portable refrigeration unit, thus improving thermal stability with the withstand voltage from 1040 V to 1140 V. Compared with the devices without semiconductor refrigeration, the chromium was excited more favorable when the discharge voltage increased, and the limit of detection (LOD) decreased by 8.5 times. Furthermore, the LODs of Zn, Cd, Ni, Cu and Pb decreased by 1.8–3.2 times, respectively, which realized the detection of elements in electroplating sewage and showed high performance in the field of trace elements analysis. Furthermore, the accuracy of the method was verified by stream sediment reference material (GBW07312), and the results were consistent with the certified values. The recoveries of elements added to industrial sewage and seawater range were from 90.5 to 98.7%, demonstrating good accuracy of the proposed method.

Enhanced Sensitivity for the Determination of Lithium by Miniaturized Liquid Cathode Glow Discharge (LCGD) Atomic Emission Spectrometry (AES) with the Addition of Surfactants

A miniature atomic emission spectrometry (AES) was developed using a liquid cathode glow discharge (LCGD) as an excitation source and optical fiber spectrometer as the detection system. The instrument was employed for the sensitive determination of lithium (Li). The addition of 0.15% cetyltrimethylammonium chloride (CTAC), 0.15% cetyltrimethylammonium bromide (CTAB) and 3 critical micelle concentration (CMC) Triton X-405 enhanced the Li emission by 3.7-, 3.2-, and 1.8-fold, respectively. The presence of 50 mg L−1 Al3+ and SO4 2− inhibited the recovery of 0.5 mg L−1 Li about 73% and 75%, respectively. After adding CTAB, CTAC, and Triton X-405, the recovery of Li was from 98% to 108%, suggesting that the addition of surfactant eliminated the Al3+ and SO4 2− interferences. The sensitivity of Li was improved by adding the surfactants by factors of 2.3 for 0.15% CTAB, 2.0 for 0.15% CTAC, and 1.9 for 3 CMC Triton X-405. The limit of detection (LOD) with 0.15% CTAB for Li was 0.55 μg L−1 which was improved by 5.6-fold. In addition, the energy consumption was below 60 W and good precision was obtained. The accuracy, reliability, and repeatability of the proposed method were verified by analysis of water samples and satisfactory recoveries between 91% and 115% were obtained. The results demonstrate that LCGD-AES with surfactants can be used for highly sensitive determination of Li in complex samples because of its low cost, small size, and low power consumption.

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.

Multi-Element Simultaneous Sensitization of Solution Cathode Glow Discharge Atomic Emission Spectrometry by Using Portable Semiconductor Anode Refrigeration

Multi-Element Simultaneous Sensitization of Solution Cathode Glow Discharge Atomic Emission Spectrometry by Using Portable Semiconductor Anode Refrigeration

Ultra-sensitive determination of mercury by atmospheric pressure glow discharge atomic emission spectrometry coupled with cold vapor generation

In this work, DC glow discharge atomic emission spectrometry coupled with cold vapor generation was used to achieve the ultra-sensitive analysis of mercury, with good anti-interference ability.

Direct Ultratrace Detection of Lead in a Single Hair Using Portable Electromagnetic Heating Vaporization-Atmospheric Pressure Glow Discharge-Atomic Emission Spectrometry.

In this paper, the first demonstration of direct ultratrace determination of lead in a single human hair by direct current-atmospheric pressure glow discharge-atomic emission spectrometry (DC-APGD-AES) coupled with electromagnetic heating vaporization (EMV) was described. Only the ultramicro mass of a human hair sample (about 0.15 mg, often a single human hair) was required during the analysis, and fast detection was implemented without tedious pretreatment processes, such as grinding and digestion. A limit of detection (LOD) of 30.8 μg kg-1 (4.8 pg) for Pb was obtained under optimized conditions, which was even equivalent to that of conventional LA-ICP-MS/ETV-ICP-MS/GFAAS. EMV-APGD-AES, meanwhile, can facilitate miniaturization and portability with low power and small size. The accuracy and practicality of the method were verified by the analysis of certified reference materials (CRMs) GBW09101b (human hair) and human hair samples from three volunteers. A simple, efficient, and low-cost method for detecting Pb in human hair has been developed.

Highly sensitive determination of cadmium and lead in whole blood by electrothermal vaporization-atmospheric pressure glow discharge atomic emission spectrometry

In this study, a fast and simple method for highly sensitive detection of Cd and Pb elements based on atmospheric pressure glow discharge atomic emission spectrometry (APGD-AES) coupling with tungsten coil electrothermal vaporization (ETV) was proposed. A small amount of sample (10 μL) was dropped onto the tungsten coil, followed by drying, pyrolysis and vaporization procedures, and then the vaporized analyte was transported to APGD for excitation. The whole procedure took approximately 3 min. Multi-step heating of the ETV unit can separate matrices and solvents from the analyte, providing an advantage in detecting samples with complex matrix. Under the optimal experimental conditions, limits of detection of 0.4 μg L−1 (4 pg) for cadmium and 1.2 μg L−1 (12 pg) for lead were obtained, with relative standard deviations of 20 μg L−1 Cd and 100 μg L−1 Pb both being <5%. The accuracy of the ETV-APGD-AES system was verified by the determination of heavy metals in whole blood standard sample (GBW(E)090,251) and the practicability of the ETV-APGD-AES system were demonstrated by the determination of heavy metals in human whole blood. The results obtained by this instrument agree well with the standard values and those obtained by ICP-MS.

Evaluation of solution-cathode glow discharge atomic emission spectrometry for the analysis of nanoparticle containing solutions

The Solution Cathode Glow Discharge (SCGD) is a novel atmospheric-pressure glow discharge plasma sustained in the ambient atmosphere that is an appealing alternative to the inductively-coupled plasma as a source for atomic emission spectrometry. Simple, low power, and inexpensive, the SCGD is an attractive source for continuous environmental monitoring applications such as the quantitation of metallic nanoparticle solutions by atomic emission spectrometry. Metallic nanoparticles (NP) with diameters from 5 nm-150 nm were directly analyzed by SCGD-AES and found to exhibit lower, and size-dependent, elemental sensitivity when compared to dissolved free-ion standard solutions. Acid digestion with matrix-matching was shown to be an effective approach to achieve accurate quantitation. The origin of these morphological matrix effects was studied by investigating experimental parameters such as discharge power, solution flow rate, and influence of added surfactants. Examination of the spatial distribution of atomic emission between cathode and anode showed a shift in peak atomic emission towards the anode of the SCGD for some NPs as compared to free-ion solutions. A novel nested capillary design was used to introduce NP into the SCGD without dissolution within the acidic solvent and showed difference in sensitivity from free-ion solutions to be a NP morphological effect. Correlation of NP boiling point with difference in sensitivity between free-ion and NP solutions supports the conclusion that delayed vaporization of nanoparticles is the source of the morphological matrix effect, due primarily to lower rate of vaporization within the SCGD by lower gas temperatures and short residence time. Analysis of NP of different chemical form, and alloyed nanoparticles composed of more than one element, showed correlation with boiling point. Implications of these results on the possible mechanisms by which material is transferred from the liquid cathode into the plasma are considered.

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.

Ultrasensitive determination of mercury by solution anode glow discharge atomic emission spectrometry coupled with hydride generation

An innovative method for the ultrasensitive detection of mercury by solution anode glow discharge atomic emission spectroscopy (SAGD-AES) coupled with hydride generation (HG) was first investigated. In this method, the mercury vapor generated by the HG was transmitted to the SAGD through the miniature hollow tungsten tube for excitation and detected by a miniaturized spectrograph. A thorough parametric evaluation of the HG and SAGD system was performed, including the type and concentration of carrier acid, He flow rate, concentrations of NaBH4, discharge current and discharge gap. Under optimal operating conditions, the detection limit for Hg2+ achieved 0.03 μg/L, with a relative standard deviation of 1.1% at the Hg2+ concentration of 5 μg/L. Moreover, the correlation coefficient of the calibration curve was 0.9996 in the range between 0.1 and 10 μg/L. The accuracy and practicability of HG-SAGD-AES were verified by measuring GBW09101b (human hair), GBW10029 (fish), soil and rice samples. The results showed good agreement with the certified values and values from direct mercury analyzer (DMA).

Simplified design for solution anode glow discharge atomic emission spectrometry device for highly sensitive detection of Ag, Bi, Cd, Hg, Pb, Tl, and Zn

Herein, we propose a simplified design for a solution anode glow discharge-atomic emission spectrometry (SAGD-AES) device for determination of Ag, Bi, Cd, Hg, Pb, Tl, and Zn concentrations in solutions with high sensitivity. Using a Ti rod as the cathode, the need for a cooling device and noble gas environment was eliminated, which would enable the miniaturization of the device in the future. Moreover, the quartz tube in the device was directly connected to the graphite rod to eliminate the need to maintain a constant sample solution level in the device during discharge. A thorough parametric evaluation of the proposed SAGD-AES for heavy metal determination was performed. Our proposed SAGD-AES device achieved detection limits of 0.03, 1.98, 0.07, 1.7, 1.35, 0.02, and 0.12 μg L−1 for Ag, Bi, Cd, Hg, Pb, Tl, and Zn, respectively, with the corresponding relative standard deviations for analyte concentrations of 10 μg L−1 (Ag, Cd, Tl, Zn) and 200 μg L−1 (Bi, Hg, Pb) being <5%. The accuracy of the proposed SAGD-AES design was experimentally verified by the determination of heavy metal concentrations in a simulated natural water sample (GBW08607) and in waste laboratory liquid. The results obtained using our device were in good agreement with those obtained using inductively coupled plasma mass spectrometry.

A liquid chromatography detector based on continuous-flow chemical vapor generation coupled glow discharge atomic emission spectrometry: Determination of organotin compounds in food samples

A novel liquid chromatography (LC) detector based on continuous-flow chemical vapor generation (CVG)-coupled glow discharge (GD) atomic emission spectrometry (AES) was proposed herein for the simultaneous determination of organotins (OTs) in food samples. OTs were separated on an LC column and converted into volatile gases by the CVG technique. The GD microplasma was used to excite the Sn atoms to generate the special atomic emission lines of Sn at 317.66 nm, which were recorded by a charge-coupled device (CCD) spectrometer. For an injection volume of 1 mL, the linear correlation coefficients (R) were higher than 0.99 in the concentration range from 0.1 to 10 μg mL−1. The recoveries of OTs from spiked samples were 70–103%, and the relative standard deviations (RSD) were 0.2–8.7%. The limits of detection (LOD) for the tested OTs, i.e. trimethyltin chloride (TMT) and dimethyltin dichloride (DMTC), were determined to be 0.59 and 0.93 μg L−1, respectively. The CVG-GD-AES detector can be used to simultaneously determine TMT and DMTC with high sensitivity, in a simple and cost-effective manner.

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.