用于MIP-AES的气动雾化法的研究

水溶液样品经气动雾化后引入低功率微波诱导等离子体, 由于采用了新的去溶系统和分离器, 大大改进了微波诱导等离子体原子发射光谱法的光谱分析性能。详细考察了各实验参数对测定一些元素的影响。这些元素的检出限和测定精密度令人满意。     

Spray nebulization for sample introduction in ion mobility spectrometry

A new sample introduction system based on spray nebulization has been successfully developed to perform direct analysis of liquid samples by IMS. The system comprises a concentric nebulizer that generates a spray plume which is introduced in the ionization region of the IMS instrument through a temperature controlled transfer line. This system avoids previous problems of direct injection of liquid samples and maintains the countercurrent flow of inert gas necessary for the operation of the IMS instrument. Evaluation of the qualitative and quantitative capabilities of the methodology has been performed after a carefully study of the main variables affecting the spray nebulization and the transport of the analyte molecules through the transfer line. To demonstrate the usefulness of the new sample introduction system, direct analysis of drugs and drug metabolites in saliva or urine samples have been performed, obtaining accurate, reliable and sensitive results. Moreover, analytes with physico-chemical properties that limited the capability of thermal desorption as sample introduction method such as amino acids can be analyzed by using the spray nebulization methodology.     

Improvement of the power of detection in ICP/OES by a new way of sample introduction (hydraulic high-pressure nebulization)

Summary During an ICP-/OES procedure, the application of an aerosol solely created by a very high hydraulic pressure (1000 to 5000 psi) is employed for sample introduction (HHP-nebulization). The BEC-values achieved are lower by a factor of 1.7 to 3.6 in comparison to pneumatic nebulization.

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Steigerung des Nachweisvermögens in der ICP/OES durch eine neue Art der Probeneinführung (hydraulische Hochdruck-Zerstäubungstechnik)

     

Characterization of aerosols generated by thermospray nebulization for atomic spectroscopy

The performance of an inductively coupled plasma (ICP) for atomic emission spectroscopy (AES) is strongly dependent upon the sample introduction system. The Thermospray Vaporizer has recently been shown to yield enhanced sensitivity compared to conventional pneumatic nebulizers when used as a sample introduction source for the ICP. This report is a study of the properties of the aerosols produced by the thermospray. Aerosol particle diameter distributions have been related to droplet size distribution and nebulization efficiencies as a function of the relevant variables of the nebulization system. The results help explain high emission intensities and lower detection limits achieved using the thermospray. The higher efficiencies with thermospray, compared to conventional pneumatic nebulization, also makes the thermospray a prime candidate for sample introduction into molecular gas ICPs.     

化学蒸气发生-非色散原子荧光光谱技术的发展

紫外光化学蒸气发生（UV-PVG）是一种绿色的样品引入技术,作为接口已被成功应用于结合光谱与质谱检测领域,实现对目标元素的检测. 方法简单高效,试剂用量少,可用于现场式检测. 同时,UV-PVG也拓宽了化学蒸汽发生元素范围,不仅可应用于As、Hg、Sb、Pb等可氢化物发生元素,还可以应用于过渡金属元素包括Cd、Fe、Co、Ni、Os以及非金属元素中的I、Br. 从机理推测、应用范围、优缺点和发展趋势方面对UV-PVG进行了阐述.     

A new nebulization device with exchangeable aerosol generation mode as a useful tool to investigate sample introduction processes in inductively coupled plasma atomic emission spectrometry

A new sample introduction device has been designed in order to differentiate between the effects of the aerosol production and its following desolvation on analytical performances of an inductively coupled plasma optical spectrometer. This research tool allows to easily switch between the pneumatic and ultrasonic aerosol generation mode and to use a joint desolvation chamber. In this way, a real comparison between aerosol production systems may be attained and the influence of aerosol generation process on analytical figures clearly distinguished from that of the desolvation process. In this work, the separate effects of the aerosol generation and desolvation processes on analytical sensitivity and tolerance towards matrix effects have been investigated. Concerning sensitivity, it was found that both the processes play an important role in determining emission intensities, being the increase in sensitivity due to desolvation higher than that due to the improved aerosol generation efficiency. Concerning the matrix effects, a predominant role of the desolvation system was found, while the influence of the aerosol generation mode was much less important. For nitric acid, the decreasing effect was mitigated by the presence of a desolvation system, due to partial removal of the acid. On the contrary, the depressive effect of sulfuric acid was enhanced by the presence of a desolvation system, due to degradation of the solvent removal efficiency and to further decrease in the analyte transport rate caused by clustering phenomena. Concerning the interferences due to sodium and calcium, a depressive effect was observed, which is enhanced by desolvation.     

New developments in thermospray sample introduction for atomic spectrometry

The status of thermospray sample introduction for analytical atomic spectrometry was last reviewed in 1992. In this review, we summarize developments in this field since that time, including investigations of aerosol generation processes, noise diagnosis and control with inductively coupled plasma-atomic emission or mass spectrometry (ICP-AES/MS), high flow thermospray, the use of dual-stage desolvation systems based on membrane dryers, and the utilization of thermospray with axially viewed ICP-AES. Since a major advantage of methods based on thermospray is improved limits of detection, the emphasis for applications of thermospray with ICP spectrometries remains focused on environmental sample types, particularly with ICP-MS. Relatedly, the use of thermospray as a means for the direct speciation of Se is also under development.     

Photo-induced chemical-vapor generation for sample introduction in atomic spectrometry

Chemical-vapor generation (CVG) is widely used as a sample-introduction technique for atomic spectrometry, with the advantages of efficient matrix separation, high analyte-transport efficiency, and high selectivity and sensitivity. Recently, photo-induced CVG (photo-CVG) was demonstrated to be a powerful alternative to conventional CVG. In photo-CVG, volatile species (including hydrides, elemental, carbonylated and alkylated analytes) are generated from non-volatile precursors by ultraviolet irradiation in the presence of low-molecular-weight organic compounds. Photo-CVG is simple, fast and environmentally friendly with little interference from transition metals. Its analytical applications have been demonstrated in analysis of Hg, conventional hydride-forming elements (As, Bi, Sb, Se, Te), transition metals (Ni, Co, Fe) and non-metals (I). In addition, photo-CVG was developed as a simple, effective interface between high-performance liquid chromatography (HPLC) and atomic spectrometry. This review summarizes the applications of photo-CVG for various analytes and as a novel interface between HPLC and atomic spectrometry. We also discuss current research on the possible reaction mechanism of photo-CVG.     

High-performance flow atomic spectrometry: New nebulization techniques,on-line speciation and on-line sample pretreatment

An interface-free combination of HPLC separation techniques and methods for element determination by atomic spectrometry can be achieved by hydraulic high-pressure nebulization (HHPN). With high-temperature HHPN (300 ( degrees )C) super heated liquids can be nebulized providing aerosol yields of up to 90% in flame AAS. This new nebulization method combines the advantages of HHPN and thermospray techniques (very small aerosol droplets, high aerosol yield, nebulization of saturated salt solutions).     

High-performance flow atomic spectrometry: New nebulization techniques, on-line speciation and on-line sample pretreatment

An interface-free combination of HPLC separation techniques and methods for element determination by atomic spectrometry can be achieved by hydraulic high-pressure nebulization (HHPN). With high-temperature HHPN (300^°C) super heated liquids can be nebulized providing aerosol yields of up to 90% in flame AAS. This new nebulization method combines the advantages of HHPN and thermospray techniques (very small aerosol droplets, high aerosol yield, nebulization of saturated salt solutions).     

Evaluation of a hollow cathode atomic emission source designed for continuous solution sample introduction

A hollow cathode discharge capable of continuous operation with solution sample introduction is described. Discharge current densities up to 0.64 are maintained in a helium plasma. Analyte emission intensities are optimized in terms of anode placement in relation to the hollow cathode, carrier gas flow rate, discharge current and sample solution flow rate. Detection limits for selected elements are reported and range from 0.03 for Li to 200 for Zn. Temporal stability of the discharge is examined and a calibration curve for Li is presented.     

Characterization of a membrane interface for sample introduction into atom reservoirs for analytical atomic spectrometry

This paper describes and characterizes a new interface for organic solvent sample introduction into atom reservoirs for analytical atomic spectrometry, especially for inductively coupled plasmas. The unoptimized analyte transport efficiencies were in a range between 45 and 65 % and the solvent removal efficiencies were 80–100 % using Freon and chloroform as solvents. The interface gives - for inductively coupled plasmas - a higher analyte transport efficiency at optimum solvent load in comparison with normal nebulizer systems. The interface is easy to optimize since all gas and liquid flows can be varied independently. The interface provides for optimum coupling of analytical liquid flow techniques to instruments for analytical atomic spectrometry.     

The graphite filter furnace: a new atomization concept for atomic spectroscopy

A new atomization concept for electrothermal atomic absorption spectroscopy (ETAAS) is proposed and discussed. The basic idea is to form within part of an atomizer a large surface over which the collection of fine particles of the sample is to be distributed, and to constrain the vapor exit from that part to the analytical zone. For the amounts of analyte which are in the range of ordinary ETAAS, these techniques do not affect the character of atomic vapor release because the surface area for the analyte is smaller than that of the vapor passage. However, when there is an excess of matrix, this technique creates the conditions for matrix vapor saturation which impedes the evaporation. This in turn restricts the concentration of matrix vapor in the analytical zone and, respectively, limits spectral background and gas-phase chemical interferences. The concept is realized in the design of a graphite filter furnace. The principle of operation of the atomizer and practical methods to obtain analytical advantages are discussed and compared, using experimental data.     

Chemical vapor generation for sample introduction into inductively coupled plasma atomic emission spectroscopy: vaporization of antimony(III) with bromide

A new method for antimony determination in soils is proposed. It is based on the chemical vapor generation of Sb(III) with bromide, after a reaction in sulfuric acid media and transport of the gaseous phase into an inductively coupled plasma for atomic emission spectrometry. The experimental variables influencing the method were delimited by experimental design and the most important were finally optimized by the modified Simplex method. In optimized conditions the method involves the reaction of 579 microl concentrated sulfuric acid with 120 microl 5% w/v KBr and 250 microl antimony solution. Measurement of antimony emission intensity at 217.581 nm provides a method with an absolute detection limit of 3.5 ng and a precision (RSD) of 5.8% for the injection of five replicates of 175 ng Sb(III) (250 microl of 0.7 microg ml(-1) solution). The interference of common anions and cations on the antimony signal was evaluated. A 21% Sb(III) volatilization efficiency was calculated from the mean of six experiments at optimum conditions. The accuracy of the methodology was checked by the analysis of one standard reference soil after acid decomposition heating in a microwave oven.     

Particle sample introduction system for inductively coupled plasma–atomic emission spectrometry

Development and characterization of a new, relatively inexpensive, computer-controlled, particle sample introduction (PSI) system for programmable delivery of small amounts of diluted powdered samples into an inductively coupled plasma (ICP) and measurement by atomic emission spectrometry (AES) is described. The PSI was developed for use with non-hygroscopic particles, in particular those with a particle weight in the ng range (i.e., with a diameter in low μm-range) and for solids that can be converted to a powder (i.e., a collection of particles). In this first report on PSI–ICP–AES, linearity of calibration curves and plasma loading concerns were addressed using three modes of operation. In the first mode, the PSI operated similar to a nebulizer and it delivered to the plasma for a period of 5–10 s a relatively constant amount of particles diluted with graphite. In the second mode, the PSI delivered to the plasma a small “puff” of a diluted sample, thus generating a transient, time-domain signal with duration of about a second. In the third mode, an even smaller “puff” was delivered to the plasma and, using high-speed data acquisition (in the kHz range), time-resolved emission signals from individual, μm-diameter and ng-weight particles were observed. Thus, the PSI can also be thought of as a nano-particle (i.e., ng rather than nm) sample introduction system. Similarly, the high-speed, wide-bandwidth single-channel time-resolved data acquisition mode enabled the determination of particle-size distribution. In addition, a dual-channel (or dual-element) mode enabled homogeneity studies on a per-individual-particle basis. In all modes, linear calibration curves were obtained (provided that plasma loading was avoided). Per-cent relative standard deviation ranged between 3.1% and 4.2% for Ni in certified reference materials but was as high as 50% for heterogeneous soil samples. Tungsten emission signals from refractory tungsten carbide powders were enhanced using mixed gases and by modifying the chemical environment of the ICP using SF₆. Furthermore, when coupled with high-speed data acquisition, PSI brought unique capabilities to ICP–AES for homogeneity studies from individual ng-weight particles and for the determination of particle size distributions. Overall, it was concluded that PSI is an attractive alternative to powder sample introduction systems described in the literature.     

An improved monosegmented continuous-flow system for sample introduction in flame atomic spectrometry

A monosegmented system for sample introduction which does not require air removal is proposed. The sample is intercalated into an unsegmented carrier stream together with air plugs. Segmentation involving the placement of a single air plug in the tailed portion of the sample is also investigated and compared with the original approach in which the sample is introduced between two air bubbles. Effects of sample volume (25–1000 μl) and length of the air plugs (5–200 cm) on the recorded peak and measurement reproducibility are discussed. Flame instability caused by the air plugs is not a problem with the larger samples. The single-line system proposed for determination of zinc in plant digests is very stable. Limited dispersion is achieved by injecting only about 100 μl of sample; a sampling rate of 400 measurements per hour at the 1% carryover level can be attained. Precise results (r.s.d. ca. 1%) in agreement with those obtained by conventional atomic absorption spectrometry (a.a.s.) are achieved. The advantages of the proposed system compared to a conventional flow-injection system for a.a.s. are emphasized. The determination of calcium in natural waters demonstrates the feasibility of monosegmentation when a reagent solution must be added. Lanthanum solution can be added by merging zones or by confluence, either before or after the sample injection. The accuracy, precision, sample consumption and system stability attained are favourable.     

Thermospray nebulizer as sample introduction technique for microwave plasma torch atomic emission spectrometry

A thermospray nebulizer was used as a sample introduction device for microwave plasma torch (MPT) atomic emission spectrometry (AES). Experimental parameters, including the power supplied to the MPT, the flow rates of support and carrier gases, the observation height, the sample uptake rate, the thermospray working temperature, the temperature of the aerosol spray chamber and cooling water were optimized. Under optimum conditions, the relative standard deviation (RSD) of 10 measurements for 21 elements is in the range 0.3–2.0%. The detection limits were improved in comparison with the ultrasonic nebulizer as sample introduction technique for MPT–AES. The inclusion of 20% methanol into the MPT showed there is no effect on the stability of MPT discharge. The technique can thus be held to have the potential for interface to reverse-phase HPLC systems.