Solid Sample Introduction Research Articles

Electrospray mass spectrometry of trimethyllead and triethyllead with in-tube solid phase microextraction sample introduction

A study of positive ionization electrospray mass spectrometry (ES-MS) was performed on trimethyllead (TML) and triethyllead (TEL). The system consisted of in-tube solid phase microextraction (SPME) coupled directly to an electrospray mass spectrometer. Fragmentation patterns of compounds were observed by applying different fragmentation voltages. High voltages produced sufficient fragmentation to elucidate the dissociation of the trialkyllead compounds. Electrospray mass spectrometry has been shown to be a suitable detection system for organolead speciation. Applying fragmentation energy programming, it might be possible to obtain in parallel the molecular and atomic signals of lead compounds. Copyright 1999 John Wiley & Sons, Ltd.

Studies on the Fundamental Characteristics of Laser Ablation/Low-Pressure Inductively Coupled Plasma

We designed a low-pressure inductively coupled plasma (LP-ICP) with a laser ablation chamber that was used for solid sample introduction, and we investigated the fundamental characteristics of Ar and He ICPs with the LP-ICP. Fundamental characteristics of Ar and He ICPs at low pressure were studied by measuring excitation temperature and electron number density as operating conditions such as forward power, discharge gas flow rate, and pressure were varied. Excitation temperatures of Ar and He LP-ICPs were independent of the operating conditions, but the electron number density of Ar ICP showed a significant change as the operating conditions were varied. The electron number density of He LP-ICP could not be determined because the Stark width of He LP-ICP was too small to be measured with the resolution of the spectrometer employed in this work. The excitation temperatures of Ar and He LP-ICPs were approximately 4200–4500 K. The electron number density values of Ar LP-ICP were found to range from 2.63 × 1014 to 5.75 × 1014.

Laser ablation and arc/spark solid sample introduction into inductively coupled plasma mass spectrometers

Sample introduction using laser ablation and arc and spark ablation is reviewed. Few references were found in the literature on the use of spark or arc ablation as a sample introduction technique into the ICP-MS and emphasis is therefore placed on the use of laser ablation sampling, particularly for Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection; however, many of the principles can also be applied to optical emission detection. The applications of the techniques are described, with particular emphasis on micro-sampling of geological materials.

Multielement Analysis of Graphite and Silicon Carbide by Inductively Coupled Plasma Atomic Emission Spectrometry Using Solid Sampling and Electrothermal Vaporization

An improved graphite furnace electrothermal vaporization device, equipped with an autosampler system for precise and almost contamination-free introduction of solid samples, was used for the simultaneous determination of Al, Ag, As, Bi, Ca, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Na, Ni, and Pb in graphite and silicon carbide by inductively coupled plasma atomic emission spectrometry. The volatilization of most analytes could be significantly improved by addition of Freon 1,2 to the argon carrier gas. Calibration was performed using aqueous standard solutions. Owing to the extremely low blanks, large applicable sample portions (up to 16 mg), high transport efficiency, and the addition of Freon 1,2, extraordinarily low limits of detection in the range 5−250 ng/g were achieved. The accuracy was checked by comparison of the results with those obtained by various other methods. For most analytes in both matrixes, the comparison led to very good agreement of the results.

Calibration of laser-ablation ICP-MS. Can we use synthetic standards with pneumatic nebulization?

An approach for the determination of trace element concentrations in high purity metals, using an inductively coupled plasma mass spectrometer (ICP-MS) with a laser-ablation system for direct solid sample introduction after calibration with nebulized liquid standards was made. Due to the inherent differences in the rate of sample introduction with laser-ablation and pneumatic nebulization, a matrix element must be used as an internal standard. This is problematical for elements that have no isotope with a relative abundance of less than 0.1 %, since the ion signals would be too high for direct measurement, and reduction of the ablation rate would compromise the sensitivity for trace elements. Due to the high stability of ICP-unit and mass filter of the instrument used, it was found that the tail of a mass-peak of the matrix element could be used as an internal standard. Therefore, a position at –0.5 amu from the matrix-isotope (e.g. 62.5Cu in copper samples) was used for internal standardization. The standard deviation of this signal in a period of 2.5 h was 3.6% RSD with no notable drift when the laser ablation was used for sample introduction. The calibration of the matrix-element by nebulizing liquid standards showed that the ion signal measured on the peak-tail is directly proportional to the element concentration in the ICP. This indicates that the peak shape is not only stable, but also independent of the peak height. The advantages of this method lie in the easy preparation of calibration standards for quantitative measurements with a laser-ablation system and access to homogeneous standards for materials, that are difficult to homogenize in the solid state. The calibration of the traces is performed relatively to a fixed concentration of the matrix element. Calibrations were carried out for trace concentrations in high purity copper and good recoveries were obtained for high-purity reference standards.

Laser ablation sampling

Laser ablation sampling provides significant benefits and capabilities for chemical analysis. It represents one of the most promising technologies for direct solid sample introduction. Despite the advantages, there are a number of issues that should be addressed to better understand and utilize this technology. Laser ablation itself is a complex process and is poorly understood, fundamentally. In this paper, we describe the current achievements and limitations in order to better understand and utilize laser ablation sampling for chemical analysis. Several current issues related to laser ablation sampling are discussed, including calibration and optimization, fractionation, sensitivity enhancements, mass loading, and particle transport.

Rapid and simultaneous multi-element analysis of atmospheric particulate matter using inductively coupled plasma mass spectrometry with laser ablation sample introduction

A precise and accurate method of analysis using inductively coupled plasma mass spectrometry combined with laser ablation for direct solid sample introduction was developed for the determination of Na, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sb, Ce, W and Pb in atmospheric particulate matter. Analyte element calibration was performed easily using a standard filter sample prepared by dropping an aqueous standard solution on to the surface of the same type of membrane filter as used for collecting atmospheric particulate matter. The absolute limits of detection ranged from 1.2×10–3 ng for Ce and W to 56.6 ng for Na. For replicate determinations of the analyte elements, the repeatabilities were within 10% (as RSD), except for Al (11%), Cu (18.5%) and Ag (16%). The method was successfully applied to the determination of trace elements in atmospheric particulate matter collected in Tokyo, Japan. The analytical results were in good agreement with those obtained by the commonly used method of instrumental neutron activation analysis.

Applications of Laser-Induced Breakdown Spectrometry

INTRODUCTION When a high-powered laser beam is focused onto a small area or spot of a solid surface, the temperature of the locally heated region rises rapidly to the vaporization temperature of the solid material and an optically induced plasma, frequently called a laser-induced plasma (LIP) or laser-ablated plasma (LAP) or laser spark is formed at the surface. The plasma will be formed when the laser power density exceeds the breakdown threshold value of the solid surface. Although different materials have different breakdown thresholds, an optical plasma is produced when the laser power density exceeds several megawatts per centimeter squared (106 - 109 W/cm2). This plasma has been used for sampling, atomization, excitation, and ionization in analyhcal atomic spectroscopy. It has also been frequently used and proposed as a source for atomic emission spectrometry (AES). In this case the technique is most ofien referred to as laser microprobe optical emission spectrometry (LM-OES) developed by Brech and Cross [1] in early nineteen-sixties or more recently called laser-induced breakdown spectrometry (LIBS) [2,3]. Generally, this analyhcal technique involves two steps; the pulsed focused laser beam directed into a gaseous sample or the surface of a solid or liquid, to produce a transient LIP, followed by the measurement of a characteristic atomic emission signal related to some species present in the plasma. The LIP formed is tightly focused and consists of vaporized atoms, ions, electrons, and molecular fragments. The application of LIBS for direct spectrochemical analysis is a rapidly growing field ranging from the detection of atmospheric pollutants to monitoring of material production processes, and even to “clean-room” technology. Laser ablation techniques have also been applied for solid sample introduction into other plasma sources [4–9]. In recent years, the powerful technique of LIBS as an analytical tool has been recognized by a number of research groups, and has led to an increasing number of publications on the applications of LIBS both in the laboratory and in industry. This growing success of LIBS is a result of thorough research carried out to understand the related plasma physical processes, aided by marked improvements in laser systems and photodetector technology.

Electrothermal Vaporisation System Including In Situ Digestion for the Direct Determination of Lead in Botanical Samples by Inductively Coupled Plasma Atomic Emission Spectrometry

A new approach to in situ solid sample digestion, subsequent vaporisation and introduction into an inductively coupled plasma, was developed for the direct determination of lead by atomic emission spectrometry. A powdered sample was mixed with diammonium hydrogenphosphate and the mixture was weighed in a sample cuvette made of tungsten. The cuvette was then placed on a tungsten boat furnace (TBF) and tetramethylammonium hydroxide solution was added to the mixture. After the in situ wet digestion was completed and the excess reagents were evaporated by the resistance heating of the TBF, the analyte in the sample cuvette was vaporised and introduced into the plasma. The solid samples were analysed by using a calibration curve prepared from the aqueous standard solutions. In this communication, system characterisation with lead and its analytical results in several biological samples are described.

Direct Processing and Analysis of Solid and Other Complex Samples with Automatic Flow Injection Systems

Abstract The use of a suitable sampling or sample-processing unit connected to a flow injection system can significantly expand the scope of application of the flow injection technique by enabling the direct introduction and treatment of solid and other complex samples in a single automated system. In recent years various sample pretreatment techniques, including electrolytic dissolution, on-line leaching, continuous microwave digestion, on-line sterilizable membrane dialysis/filtration, pervaporation, dynamic gas-extraction, and flow-reversal liquid-liquid extraction, among others, have proven useful for solving a variety of analytical problems in conjunction with flow injection systems. The principles behind these techniques and their applications in fast assay and on-line process monitoring are reviewed and discussed. Selected major advances in this research field are outlined.

Laser ablation solid sampling: vertical spatial emission intensity profiles in inductively coupled plasma

Spectral emission intensity in the inductively coupled plasma (ICP) was measured versus height above the load coil during laser ablation solid-sample introduction. The laser-beam pulse width, power density, and wavelength, and the sample composition are know to effect the particle size distribution of the ablated mass. Ceramic and metal samples were ablated using nanosecond and picosecond pulses, and provided similar emission intensity profiles for common elements, indicating that changes in the particle size distribution are not manifested in the vertical spatial emission profile. The gas environment in the ablation chamber also influences the particle size distribution as well as the ablation interaction. Gas composition will influence the spatial emission intensity profile because of changes in the excitation characteristics of the ICP. A preliminary study using noble gases in the ablation interaction was conducted by keeping the spatial profile constant, maintaining a constant total gas composition to the ICP.

Geoanalysis using plasma spectrochemistry - milestones and future prospects.

Highlights of plasma spectrochemistry in geoanalysis are reviewed. The techniques are evaluated in terms of recent instrumental developments, calibration strategies, spectral and matrix interferences and analytical performance. While acid decomposition results in solutions containing low salt contents, this decomposition strategy is inappropriate for numerous sample types due to poor recoveries. On the other hand, alkali fusions result in total decomposition, but solutions containing high salt contents constrain the accuracy due to interference effects in the inductively coupled plasma (ICP), the sample introduction system, and in the quadrupole mass spectrometer interface. Therefore, practical limits of determination are evaluated in terms of salt tolerances. It is concluded that ICP-atomic emission spectrometry (AES) is employed mainly for the accurate determination of the major and minor elements and the more abundant trace elements. On the other hand, ICP-mass spectrometry (MS) is used mainly for the determination of trace elements and together with the possibility of obtaining some isotopic information, it profoundly enhances the capability for solving geochemical problems. Several methods of direct solid sample introduction are described. These include direct current (DC) arc emission spectroscopy (DC-AES), slurry nebulization (SN), spark ablation (SA), laser ablation (LA) and glow discharges (GD). These devices allow direct solid analysis of bulk samples, single minerals and inclusions.

Application of an ETV-ICP system for the determination of elements in human hair

When determining element contents in hair samples without sample digestion it is necessary to analyze large sample volumes in order to minimize problems of inhomogeneity of biological sample materials. Therefore an electrothermal vaporization system (ETV) is used for solid sample introduction into an inductively coupled plasma (ICP) for the determination of matrix and trace elements in hair. This paper concentrates on the instrumental aspects without time consuming sample preparation. The results obtained for optimization tests, ETV operating parameters and ICP operating parameters, are shown and discussed. Standard additions are used for calibration for the determination of Zn, Mg, and Mn in human hair. Studies including reproducibility and detection limits for chosen elements have been carried out on certified reference materials (CRMs). The determination of reproducibility (relative standard deviation (RSD) of n = 10) and detection limits (DLs) of Zn (RSD < 8.5%, DL < 0.8 μ g −1), Mn (RSD < 14.1%, DL < 0.3 μ g −1), and Mg (RSD < 7.4%, DL < 6.6 μ g −1) are satisfactory. The concentration values found show good agreement with the corresponding certified values. Further sample preparation steps, including hair sampling, washing procedure and homogenization for hair, relating to measurements of real hair samples are described.

‘Underflow’ introduction system for solid and liquid samples in bench‐top gas chromatographic/mass spectrometric systems

AbstractA simple, inexpensive inlet system was developed for the introduction of liquid and solid samples, to be employed in commercial gas chromatographic/mass spectrometric instruments, and not requiring sample injection through the chromatographic column. The system does not need any modifications of the ion source housing and pumping system and is based on admitting the sample vapour as an underflow to the normal helium flow through the chromatographic column at a location near the transfer line.

Optimization of a novel ETV system for solid sample introduction into an ICP and its application to the determination of trace impurities in SiC

The application of a novel electrothermal vaporization unit (ETV) for sample introduction into an inductively coupled plasma (ICP) is described. The system can be used for vaporizing both liquid and solid samples into an ICP or other excitation device. Exchangeable graphite cups can be used for rapid analysis of solid samples without any sample pretreatment. Free programmable, PC controlled heating cycles make it possible to use individual temperature programs to vaporize either organic or inorganic materials. By use of a computer operating parameters of the system, like ETV-temperature program, ETV-carrier gas flow rates, rf-power and observation height have been optimized with regard to the requirements of solid sampling. The system was first developed for steel analysis but was also used for investigation of environmental samples. An additional application of the system is the determination of impurities in ceramic materials like silicon carbide. Investigation indicated that PdCl 2 is a useful modifier for destruction of silicon carbide and simultaneous vaporization of the refractory impurities like aluminium, iron, vanadium and titanium. SiC samples from different manufacturers have been analysed. Concentration values of the elements investigated range from 8–950 μg g −1. On the assumption that the sample amount is about 5 mg, detection limits of the elements range from 0.3–4.4 μg g −1. Relative standard deviations of 2–14% have been found.

ChemInform Abstract: Solid Sample Introduction for Plasma Spectrometry and a Comparison of Results for Laser Ablation, Electrothermal Vaporization, and Slurry Nebulization

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Capsule-Based Microwave Digestion

Samples can be found in solid, liquid, or gaseous form. While one might argue that solids are the most ubiquitous type of sample analyzed, it would be difficult to defend the convenience of handling liquids. Indeed, most of our analytical instrumentation, from the electro-chemical through chromatographic to the spectroscopic, requires samples in liquid form. After a decade of effort in our laboratory developing solid-sample introduction methods for inductively coupled plasma emission and mass spectrometry, we have come to appreciate the convenience of liquid samples. As we approached parts per billion detection limits in solid samples using electro-thermal vaporization, we encountered inhomogeneity problems in our solid samples and standards. When tackling difficult

Communication. Assessment of direct solid sample analysis by graphite pellet electrothermal vaporization inductively coupled plasma mass spectrometry

Graphite pellet vaporization was evaluated as a method for solid sample introduction for ICP-MS. A detection limit of 0.1 ppb of Cd was obtained indicating that the technique might be very useful for screening. The accuracy was poor using the technique of external standards and four reference materials, suggesting that the technique of standard additions might be required if the technique was to be used for anything other than semi-quantitative measurements.

Review of Solid Sample Introduction for Plasma Spectrometry and a Comparison of Results for Laser Ablation, Electrothermal Vaporization, and Slurry Nebulization

The relative merits of three solid sample introduction techniques for inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry have been evaluated. The techniques studied were laser ablation (LA), slurry nebulization, and slurry introduction via electrothermal vaporization. The application of each technique to the quantification of Pa and Pb in geochemical samples has been described and the results obtained for each technique have been compared. To help in assessing the potential of the systems described here a simple classification of the agreement obtained between found and known values has been proposed allowing a comparison of these results with other results published in the literature to be made. Problems encountered during the evaluation of the techniques have been described and, for LA, the associated problems have led to the development of a modified sampling system which was used in an investigation of some fundamental aspects of LA as a method of solid sample introduction. Possible routes for improvement in sampling and transport are suggested, including use of reactive gases, ablation under stopped flow conditions and removal of large particles by gravitational settling.

Precision and accuracy of laser ablation-ICP-MS analysis of rare earth elements with external calibration

Solid sample introduction into an ICP-MS by laser ablation is an effective method for the total analysis of rare earth elements (REEs) in soils because no digestion is needed. A problem of the method, however, is the difference of the ablated mass for each laser shot. Therefore, internal standard for the compensation of signal instability, sample preparation, and the calibration method have to be carefully chosen.