Comparison of double-pulse and single-pulse laser-induced breakdown spectroscopy techniques in the analysis of powdered samples of silicate raw materials for the brick-and-tile industry

Single- and double-pulse laser-induced breakdown spectroscopy techniques applied to the analysis of pressed pellets of silicate raw materials were compared in terms of precision, sensitivity and limits of detection. Two Nd:YAG lasers (1064 and 532 mm) in an orthogonal configuration with a reheating arrangement have been employed. The main factors influencing system performance were optimized, i.e. laser pulse energies and interpulse separation. The behaviour of plasma temperature was studied over a period of time and calibration curves for Mg were constructed for both the single and double-pulse setup. When comparing the single- and double-pulse techniques, limits of detection of Si and Mg for the double-pulse technique were found to be 10 times lower.     

Study of the double-pulse setup with an orthogonal beam geometry for laser-induced breakdown spectroscopy

Single- and double-pulse laser-induced breakdown spectroscopy (LIBS) was applied on aluminum samples at atmospheric pressure in air. In the case of the double-pulse scheme, experiments were carried out with an ablation laser emitting at 532 nm and a reheating laser emitting at 1064 nm in an orthogonal beam geometry. With the use of a 1-m focal length monochromator and an echelle spectrometer both equipped with an intensified charge coupled device (ICCD), the studies on the effect of the delay between the two laser pulses displayed optimum enhancements of line emissions only at 200 ns in the reheating scheme developed here. The experimental parameters, like the signal acquisition delay, were largely studied. The line intensity enhancements were also investigated in dependence on physical parameters, such as the excitation energy levels of the lines observed. Moreover, the relative importance of ionic and neutral lines in the emission spectra was precisely characterized. From the different investigations, the behaviors of the line emissions towards the double-pulse technique were related to their excitation energy levels. A correlation between the increases in intensity and the excitation energy levels of the line emissions was highlighted. As a result, the reheating scheme showed improvements of sensitivity for elements emitting ionic lines compared with the corresponding single-pulse experiments.     

电感耦合等离子体原子发射光谱法(ICP-AES)测定玄武岩中的8种微量元素

采用硝酸-盐酸-氢氟酸高压封闭消解样品,电感耦合等离子体原子发射光谱法测定玄武岩中的8种微量元素。实验确定了方法的分解条件以及测定元素的检出限及干扰条件。用国家一级标准物质GBW07105(玄武岩)进行方法验证,检测结果与标准值基本吻合,符合地质矿产开发的要求。     

流动注射-氢化物发生-电感耦合等离子体发射光谱法测定环境样品中的砷

采用流动注射－氢化物发生－电感耦合等离子体发射光谱法测定环境样品中的砷。对测定条件及干扰因素进行了研究。在选定条件下，方法的检出限为0.0002mg/L，测定结果的相对标准偏差为1.25%。对几种国家标准物质进行测定，测定结果较准确。     

Some properties of a microwave boosted glow discharge source using neon as the operating gas

The use of neon as the operating gas for the analysis of aluminium samples with the microwave boosted glow discharge source has been studied. A new type of anode tube allowed the gas to enter the source near the sample surface so that more material was transported into the discharge. Erosion rates have been measured under conditions optimised for high line-to-background ratios and found to be lower than with argon (9 and 21 n/s, respectively). Despite the lower erosion rate the detection limits measured for a number of elements in aluminium are in the range 0.02-1 microg/g and comparable to those obtained with argon as the operating gas.     

Comparative study of analytical inductively-coupled argon-plasma discharges using different outer gases

The analytical capabilities of high power (2-4 kW) ICPs with argon as inner and intermediate gas and different outer gases (argon, nitrogen, oxygen and air) were studied under optimum and compromise operating conditions. Under the optimum conditions, the lowest detection limits for elements with sensitive atom lines (C, B, Zn) or ion lines (Mg, Mn, Fe, Cr, Ti, V) were achieved with argon as outer gas and an observation height of 13 mm. Under compromise conditions (3 kW, aerosol gas gauge-pressure 3 bar) the lowest detection limits for the atom lines were also found with a pure argon plasma at an observation height of 13 mm. For ion lines, however, the argon/oxygen and argon/nitrogen plasmas and an observation height of 8 mm were better. The detection limits were poorer in the presence of an aluminium matrix; under the optimum operating conditions, the relative increase in detection limit was smaller with the argon/oxygen and argon/air ICPs than with the pure argon or argon/nitrogen ICPs. It was found that the interferences arising from an easily ionizable matrix are lower with a diatomic gas than with argon as outer gas. The interferences when the argon/nitrogen, argon/oxygen and argon/air plasmas are used are similar and practically independent of the nebulizer-gas pressure applied.     

As, Cd, Cr, Ni and Pb pressurized liquid extraction with acetic acid from marine sediment and soil samples

Rapid leaching procedures by Pressurized Liquid Extraction (PLE) have been developed for As, Cd, Cr, Ni and Pb leaching from environmental matrices (marine sediment and soil samples). The Pressurized Liquid Extraction is completed after 16 min. The released elements by acetic acid Pressurized Liquid Extraction have been evaluated by inductively coupled plasma-optical emission spectrometry. The optimum multi-element leaching conditions when using 5.0 ml stainless steel extraction cells, were: acetic acid concentration 8.0 M, extraction temperature 100 °C, pressure 1500 psi, static time 5 min, flush solvent 60%, two extraction steps and 0.50 g of diatomaceous earth as dispersing agent (diatomaceous earth mass/sample mass ratio of 2). Results have showed that high acetic acid concentrations and high extraction temperatures increase the metal leaching efficiency. Limits of detection (between 0.12 and 0.5 μg g^− 1) and repeatability of the over-all procedure (around 6.0%) were assessed. Finally, accuracy was studied by analyzing PACS-2 (marine sediment), GBW-07409 (soil), IRANT-12-1-07 (cambisol soil) and IRANT-12-1-08 (luvisol soil) certified reference materials (CRMs). These certified reference materials offer certified concentrations ranges between 2.9 and 26.2 μg g^− 1 for As, from 0.068 to 2.85 μg g^− 1 for Cd, between 26.4 and 90.7 μg g^− 1 for Cr, from 9.3 to 40.0 μg g^− 1 for Ni and between 16.3 and 183.0 μg g^− 1 for Pb. Recoveries after analysis were between 95.7 and 105.1% for As, 96.2% for Cd, 95.2 and 100.6% for Cr, 95.7 and 103% for Ni and 94.2 and 105.5% for Pb.     

Differential pulse voltammetric indirect determination of aluminium in drinking waters, blood, urine, hair, and medicament samples using L-dopa under alkaline conditions

The differential pulse voltammetric (DPV) indirect determination of aluminium using L-dopa under alkaline conditions on a glassy carbon working electrode was studied. The proposed method relies on the linear decrease of the DPV anodic peak current of L-dopa with increase in the concentration of aluminium added. Under the optimum experimental conditions (pH 8.5, 0.08 M NH4Cl-NH3.H2O buffer solution, and 4 x 10(-4) M L-dopa), the linear range is 2-18 x 10(-7) M AlIII. The detection limit is 7.6 x 10(-8) M and the relative standard deviation for 8 x 10(-7) M AlIII is 3.5% (n = 8). A number of foreign species were examined as potential interferents. The method was applied to the determination of aluminium in drinking waters, synthetic renal dialysate, sodium chloride injection, sucrafate, hydrothorax, blood, urine and hair samples. The physiological significance is discussed.     

Determination of trace amounts of cadmium, cobalt, chromium, iron, molybdenum, nickel, selenium, titanium, vanadium and zinc in blood and milk by neutron activation analysis

The concentrations of Cd, Co, Cr, Fe, Mo, Ni, Se, Ti, V and Zn in biological fluids, human blood serum and market milk were determined by neutron activation analysis, with enrichment by coprecipitation. The pre-concentration of these trace elements was accomplished by converting the dissolved trace metal ions into their pyrrolidinedithiocarbamate (1-pyrrolidinecarbodithioate) chelates, followed by coprecipitation with a metal carrier such as Ni, Pb or Bi. The coprecipitation was carried out prior to irradiation for the short-lived nuclides (V, Ti and Se) and after irradiation for the other elements. The validity of the method was checked using certified biological reference materials; the concentrations of trace elements found by the proposed method agreed well with the published certified data. The limits of detection for Cd, Co, Cr, Fe, Mo, Ni, Se (obtained through the long-lived isotope 75Se) and Zn under the present experimental conditions were found to be 5, 5, 10, 520, 5, 70, 10 and 150 ng, respectively, for 5 ml of biological liquor. The limits of detection for Ti and V obtained (through their short-lived radionuclides 51Ti and 52V, respectively) were found to be 180 and 1.4 ng, respectively, for 50 ml of market milk, or 70 and 0.7 ng for 1 ml of blood serum.     

Nonmetals in the argon-inductively coupled plasma-optical emission spectrometry: I. Phosphorus, sulfur and carbon

The behavior of phosphorus, sulfur and carbon in the argon-ICP-OES was systematically investigated for a wide range of nebulizer gas flows and observation heights. Five lines of phosphorus, four lines of sulfur and three lines of carbon, which have analytical usable detection limits, were taken into consideration. The further parameter set was inspired by the needs of every-day-analysis in the laboratory, especially the low integration time that is necessary for analysis of large amounts of samples. For each element line a signal-to-noise plot was obtained with a method described earlier. The optimum conditions for the combined analysis were determined from signal-to-noise plots of those element lines with the lowest detection limits. The lowest detection limits for phosphorus (0.13 mg/L) and carbon (0.01 mg/L) are useful for solving many analytical problems. However, even the best detection limit for sulfur (2.97 mg/L) is only of limited use without further preconcentration. A major problem was the background of carbon, most probably from carbon dioxide, which increased the available detection limit to about 0.04 mg/L. Surprisingly, the best detection limits were obtained at very low observation heights, which were only a couple of millimeters above the load coil. Fortunately, all elements showed a similar behavior and so the detection limits at compromise conditions were only slightly higher compared with the single-element detection limits.     

Some properties of a microwave boosted glow discharge source using neon as the operating gas

The use of neon as the operating gas for the analysis of aluminium samples with the microwave boosted glow discharge source has been studied. A new type of anode tube allowed the gas to enter the source near the sample surface so that more material was transported into the discharge. Erosion rates have been measured under conditions optimised for high line-to-background ratios and found to be lower than with argon (9 and 21 n/s, respectively). Despite the lower erosion rate the detection limits measured for a number of elements in aluminium are in the range 0.02–1 g/g and comparable to those obtained with argon as the operating gas.     

Electron probe X-ray microanalysis of archeological finds of the Baikal region

A procedure was developed for determining Fe, Ni, Sn, and Zn in copper by electron probe X-ray microanalysis. The dependence of the detection limits for analytes on excitation conditions was studied and the optimum conditions for measuring the analytical signal were found. It was shown that the precision of quantitative electron probe microanalysis depends on the homogeneity of the reference samples. Individual certified reference samples of copper alloys previously synthesized for spectrochemical and chemical analysis were applied to electron probe microanalysis and justified. Performance characteristics of the proposed procedure were evaluated. Examples of using the procedure for determining the composition of archeological finds from a burial place in the Baikal region are presented.     

The determination of selenium by atom-trapping atomic absorption spectrometry

The application of atom-trapping atomic absorption spectrometry to the determination of selenium has been studied in detail. The optimum experimental parameters were established and the interference of major elements on the determination of selenium was studied using collection on a cold silica tube. The atom-trapping atomic absorption technique gives a detection limit of 0.03 ppm after 2-min collection on silica in an air—acetylene flame. This compares with ca. 1 ppm by the conventional absorption technique at the same 196.1-nm line. Methods to minimize interferences were examined, including the use of a double tube arrangement, an aluminium oxide-coated silica tube and ion-exchange separation. A combination of combustion in an oxygen flask and collection from an air—acetylene flame on the aluminium oxide-coated silica tube yielded satisfactory results in the analysis of four plant tissue samples.     

电感耦合等离子体原子发射光谱法(ICP-AES)测定锰结壳中的多种金属元素

采用硝酸-盐酸-氢氟酸高压封闭消解样品,电感耦合等离子体光谱法测定锰结核GBW07296和富钴结壳GSMC-1标准物质中的18种常、微量元素。实验过程中确定了最佳工作条件,选择了最佳分析谱线。实验结果表明,该方法线性相关系数良好r>0.999 8,方法检出限低,精密度高,RSD小于2.0%(n=6),可同时测定锰结壳中的多种金属元素,方法完全能满足岩石、土壤、海洋沉积物中多个元素的检测需求。     

Main parameters influencing the double-pulse laser-induced breakdown spectroscopy in the collinear beam geometry

Two Nd:YAG lasers emitting at 532 nm were combined in the same direction (collinear beam geometry) for double-pulse laser-induced breakdown spectroscopy studies on aluminum samples at atmospheric pressure in air. The influence of the delay between the two laser pulses was investigated for the background emission, for lines detected in aluminum samples and for atmospheric lines with different detection systems (photomultiplier tube, Czerny–Turner spectrometer and echelle spectrometers). The optimization of the delay between the two laser pulses depended on the excitation energy levels of the emission lines: two optima of interpulse delays were observed in the collinear geometry. Different regimes of laser–plasma interactions were discussed depending on the interpulse delay for aluminum samples. Furthermore, the effect of the sampling geometry, in terms of lens-to-sample distance, focal length of the focusing lens, was studied to determine parameters influencing the single- and double-pulse scheme. Besides, the analytical performance of the system was evaluated to characterize the advantages of the double-pulse laser-induced breakdown spectroscopy in terms of improvement of sensitivity and reduction of self-absorption effect for aluminum samples.     

Development of an accurate,sensitive, and robust isotope dilution laser ablation ICP-MS method for simultaneous multi-element analysis (chlorine,sulfur, and heavy metals) in coal samples

A method for the direct multi-element determination of Cl, S, Hg, Pb, Cd, U, Br, Cr, Cu, Fe, and Zn in powdered coal samples has been developed by applying inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with laser-assisted introduction into the plasma. A sector-field ICP-MS with a mass resolution of 4,000 and a high-ablation rate laser ablation system provided significantly better sensitivity, detection limits, and accuracy compared to a conventional laser ablation system coupled with a quadrupole ICP-MS. The sensitivity ranges from about 590 cps for ³⁵Cl⁺ to more than 6 × 10⁵ cps for ²³⁸U⁺ for 1 μg of trace element per gram of coal sample. Detection limits vary from 450 ng g⁻¹ for chlorine and 18 ng g⁻¹ for sulfur to 9.5 pg g⁻¹ for mercury and 0.3 pg g⁻¹ for uranium. Analyses of minor and trace elements in four certified reference materials (BCR-180 Gas Coal, BCR-331 Steam Coal, SRM 1632c Trace Elements in Coal, SRM 1635 Trace Elements in Coal) yielded good agreement of usually not more than 5% deviation from the certified values and precisions of less than 10% relative standard deviation for most elements. Higher relative standard deviations were found for particular elements such as Hg and Cd caused by inhomogeneities due to associations of these elements within micro-inclusions in coal which was demonstrated for Hg in SRM 1635, SRM 1632c, and another standard reference material (SRM 2682b, Sulfur and Mercury in Coal). The developed LA-ICP-IDMS method with its simple sample pretreatment opens the possibility for accurate, fast, and highly sensitive determinations of environmentally critical contaminants in coal as well as of trace impurities in similar sample materials like graphite powder and activated charcoal on a routine basis. Figure LA-ICP-IDMS allows direct multi-element determination in powdered coal samples     

Determination of As and Sb in iron and steel by neutron activation analysis with multiple gamma-ray detection

Recycled steel products demands a new technique for determining tramp elements in steel. In this paper, As and Sb in iron certified reference materials were determined by neutron activation analysis with the multiple gamma-ray detection method. The determined values are in good agreement with certified and reference values. The lower determination limits (LDL) for As and Sb in high purity iron are 0.012 and 0.0025 ppm, respectively. As the demanded LDL for As and Sb is 0.1 ppm, the method described in this work is suitable for determining As and Sb in recycled steel.     

Quality of determinations by X-ray microanalysis using standard samples of basalt glass enterprises and copper-containing alloys

Nine copper-based alloys and five man-made basalt glasses are characterized as reference samples (RS) for X-ray electron-probe microanalysis (EPMA). It is shown that the uniformity of the reference samples affects the accuracy of EPMA. The information obtained on the basis of abundant experimental data for silicate minerals, glasses, alloys, and oxides suggests that the characterized RS can be used in EPMA for analytical works, the certification of procedures, and the control of the data quality. The optimum conditions of measurements were found using the dependence of the analytical line intensity and the detection limits of the elements on the conditions of excitation and the registration of the analytical signal. The accuracy the results obtained corresponded to class 2 analyses, which suggests that the characterized RS are competitive for glasses certified as international reference samples for EPMA.     

Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 microL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 micrograms PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 microgram g-1 (Fe) and 0.08 microgram g-1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%.     

Determination of major and trace elements in human scalp hair by pressurized-liquid extraction with acetic acid and inductively coupled plasma–optical-emission spectrometry

An analytical method has been developed for determination of major (Ca, K, Mg, and Na) and trace elements (As, Cd, Co, Li, Ni, and Sr) in human scalp hair. The proposed method includes a novel, simple, rapid, highly efficient, and automated metal-leaching procedure, by pressurized-liquid extraction (PLE), combined with a rapid simultaneous detection system—inductively coupled plasma–optical-emission spectrometry (ICP–OES). PLE is one of the most promising recently introduced sample-preparation techniques, with the advantages of reducing solvent consumption and enabling automated sample handling. The operating conditions for PLE, including concentration of the extraction solvent, extraction temperature, static time, number of extraction steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio, and flush volume were studied using an experimental design (Plackett–Burman design, PBD). The optimum conditions were use of 0.75 mol L⁻¹ acetic acid as extracting solution and powdered hair samples thoroughly mixed with DE, as a dispersing agent, at a DE mass/sample mass ratio of 4. Extraction was performed at room temperature and an extraction pressure of 140 atm for 5 min in one extraction step. The flush volume was fixed at 60%. The PLE-assisted multi-element leaching proposed is complete after 7 min (5 min static time plus 1 min purge time plus 1 min end relief time). Under the optimised conditions the figures of merit, for example limits of detection and quantification, repeatability of the over-all procedure, and accuracy, were evaluated. Analysis of GBW-07601 (human hair) certified reference material revealed accuracy was good for the target elements. The optimised method was finally applied to several human scalp-hair samples.