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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A novel-pulsed electrolyte cathode atmospheric pressure discharge (pulsed-ECAD) plasma source driven by an alternating current (AC) power supply coupled with a high-voltage diode was generated under normal atmospheric pressure between a metal electrode and a small-sized flowing liquid cathode. The spatial distributions of the excitation, vibrational, and rotational plasma temperatures of the pulsed-ECAD were investigated. The electron excitation temperature of H Texc(H), vibrational temperature of N2 Tvib(N2), and rotational temperature of OH Trot(OH) were from 4900 ± 36 to 6800 ± 108 K, from 4600 ± 86 to 5800 ± 100 K, and from 1050 ± 20 to 1140 ± 10 K, respectively. The temperature characteristics of the dc solution cathode glow discharge (dc-SCGD) were also studied for the comparison with the pulsed-ECAD. The effects of operating parameters, including the discharge voltage and discharge frequency, on the plasma temperatures were investigated. The electron number densities determined in the discharge system and dc-SCGD were 3.8-18.9 × 1014 cm-3 and 2.6 × 1014 to 17.2 × 1014 cm-3, respectively. [ABSTRACT FROM AUTHOR]

Herein, a pulsed electrolyte cathode atmospheric pressure discharge (pulsed-ECAD) system was developed as a radiation source for the atomic emission spectroscope (AES) for metal element determination in aqueous solutions. The time-resolved emission spectra of the pulsed-ECAD were obtained at various frequencies, and their evolution behaviours during the modulation period were found to exhibit a strong dependence on the modulation frequency. The temporal behaviors of the metal element spectral intensities of K, Na, Li, Rb, Sr, and Mg as well as the atomic and molecular species emissions originating from water and air (OH, Hα, Hβ, N2, and O) were characterized from the plasma. The temporal evolutions of the pulsed-ECAD plasma parameters, including the rotational temperature, electron density, and ionization temperature, were analyzed. The results showed that the rotational temperatures varied between 950 K and 1350 K. The electron density and ionization temperature ranges of Mg were from 4.3 × 1014 to 2.2 × 1015 cm−1 and from 5200 K to 5500 K, respectively. [ABSTRACT FROM AUTHOR]

A novel atmospheric-pressure plasma source has been developed to determine metal ions in an aqueous solution by means of optical emission spectroscopy. In contrast to the conventional solution cathode glow discharge, this plasma source is sustained by a milli-second pulsed power supply. The electrical characteristics and spectral characteristics of the proposed plasma source are discussed. The effects of operating parameters, including pulse excitation and maintenance discharge voltage, pulse width, pulse modulation duty ratio, solution flow rate, and detector delay time, are investigated. Na, K, and Ca were observed to have a cumulative spectral emission time of 250 μs. Delayed acquisition times (in the case of maximum spectral intensity) are 500, 800, 800, 900, and 900 μs, respectively for Cu, Co, Cd, Mn, and Ag. The detection limits of trace elements such as Na, K, Cu, Co, Cd, Mn, and Ag were 0.080, 0.050, 3.4, 64, 69, 9.1, and 2.0 μg L−1, respectively. Compared to DC-excited solution cathode glow discharge, the detection performance of the above elements is observed to be increased by 2.9, 1.5, 18, 5.5, 25, 1.6, and 2.1 times, respectively. The proposed excitation source provides a promising method for detecting metal ions in aqueous solution samples. [ABSTRACT FROM AUTHOR]

A hollow anode-solution cathode glow discharge (HA-SCGD) was designed as a plasma excitation source for optical emission spectrometry. The operation parameters such as the discharge current, argon flow rate and solution flow rate were investigated. The spatial distribution profiles of normalized results of spectral bands and spectral lines were investigated and analyzed. The detection limits of Na, Li, K, Ca, Mg, Pb, Sr, Mn, Rb, Cs and Zn were 0.22, 0.69, 1.33, 240.37, 21.55, 529, 619.43, 209.51, 2.94, 7.13 and 206.95 µg L−1, respectively. The repeatability, expressed as the relative standard deviation for these elements, was determined to be within the range from 0.53 to 2.70%. The Ca, Fe, K, Mg and Na concentrations in a certified reference material were quantitatively analyzed, and the results obtained by the HA-SCGD system agreed well with the reference values. The results show that the HA-SCGD system accurately and stably determined metals in aqueous solution. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The trace mercury in an aqueous solution was determined by laser-induced breakdown spectroscopy (LIBS) with the assistance of a solution cathode glow discharge (SCGD) system. The aqueous solution was converted to the gas phase using a high voltage DC discharge, and then the generated mercury vapor was cooled by a gas–liquid separator to improve the concentration of the mercury. Finally, a 1064 nm wavelength Nd:YAG laser was used to produce the plasma. In the present experiment, the characteristic spectral line of Hg i 253.65 nm was selected for the analysis, under the optimal conditions of LIBS, to investigate the influences of the acid anion, the discharge current, the sample flow rate and the carrier gas flow rate. The temporal behavior of the electron temperature and electron number density were also investigated; the results show that the electron temperature decreases from about 10 900 K to 8800 K with a delay time from 200 ns to 6 μs and that the electron number density is in the orders of 1017 and 1018 cm−3, and decreases with delay time. The analytical performance of this method was evaluated under optimized conditions, and a calibration curve of Hg was plotted based on the different concentrations measurement results, and the detection limit (LOD) of Hg was calculated to be 0.36 mg L−1. By this experimental configuration, the detection limit and sensitivity of Hg are improved to some extent. This method provides an alternative analytical method for the measurement of trace mercury in water. [ABSTRACT FROM AUTHOR]

Fig. 1. Schematic diagram of the modified SCGD-OES system: (a) Experimental setup; (b) auxiliary cathodes with different geometry. [Display omitted] • An improved SCGD micro-plasma source was developed for the quantitative determination of heavy metal elements. • Stainless steel (316L) was used as auxiliary cathode material, which greater durability and stability, and reduced DLs. • The detection limits for K, Na, Ni, Cd, Pb, Co and Hg were comparable to other solution cathode glow discharge systems. • The results from this study may provide a new direction for the design of glow discharge sources. An improved micro-plasma source for the quantitative analysis of heavy metal elements by solution cathode glow discharge-optical emission spectrometry (SCGD-OES) was developed. The glow-discharge plasma source was fabricated using a geometrically optimized stainless steel auxiliary cathode solution and a tungsten anode. Optimum discharge could be attained at reduced solution flow rates under the following operating conditions: pH 1.0 (HNO 3); a discharge current of 80 mA; a solution flow rate of 1.65 mL/min; and a discharge gap of 2.5 mm. The detection limits (DLs) of the improved micro-plasma source for K, Na, Ni, Cd, Co and Hg were 0.17, 0.06, 18, 10, 25 and 66 μg/L, respectively. The recoveries of metal elements from spiked samples of spring river, Yangtze River and reservoir water measured by SCGD-OES showed good agreement with those obtained using ICP-OES. The results from this study may provide a new direction for the design of glow discharge sources for the in situ determination of metal elements in complex water samples. [ABSTRACT FROM AUTHOR]

Abstract: The industrial use of polyimide film is limited because of undesirable properties such as poor wettability. In the present paper, a new kind of equipment called water cathode atmospheric pressure glow discharge was used to improve the surface properties of polyimide films and made them useful to technical applications. The changes in hydrophilicity of modified polyimide film surfaces were investigated by contact angle, surface energy and water content measurements as a function of treatment time. The results obtained show good treatment homogeneity and that the variation trends of contact angles are different for polar and non-polar testing liquids, while surface energy and water content are significantly enhanced with the increase of treatment time until they achieve saturated values after 60s plasma treatment. Also, the thickness of liquid layer plays an important role in plasma processing and directly affects the treatment effect. Changes in morphology of polyimide films were analyzed by atomic force microscope and the results indicate that surface hydrophilicity after plasma treatment are improved partly due to the increase in the roughness. In addition, polyimide films treated by plasma are subjected to an ageing process to determine the durability of plasma treatment. It is found that the hydrophilicity is still better than untreated ones though the hydrophobic character partly recovers after long-term storage in ambient air. [Copyright &y& Elsevier]

Water is the most important substance for daily life and contains minerals which play an important role in nutrition. In this study, seven kinds of bottled water in Chinese market were analysed and identified by the solution-cathode glow discharge optical emission spectroscopy (SCGD-OES) combined with chemometrics methods. The score matrix was obtained by principal component analysis (PCA), and the back propagation artificial neural network (BP-ANN) model was established to identify the kind of the brands of the bottled water based on their spectral properties. The average classification accuracy based on BP-ANN is 99.74%, support vector machine (SVM) model and linear discrimination analysis (LDA) model were also employed to classify the kind of the brands of the bottled water based on the PCA analysis results, and the correct identification rate based on SVM model and LDA model are 99.50% and 98.00%, respectively. It is confirmed that SCGD-OES combined with chemometrics methods is promising for automatic real time, reliable and robust measurement, and can be integrated into a simplified form for non-specialist users. • SCGD-AES technique coupled with three chemometrics methods was employed to determine bottled water. • Based on the difference in the components and the intensities of the SC-GD emission spectra of bottled water. • BP-ANN method exhibits a better predictive power than LDA and SVM. • SCGD-AES combined with PCA and a BP-ANN is a useful technique for identification of bottled water samples. [ABSTRACT FROM AUTHOR]