Conventional Concentric Nebulizer Research Articles

Determination of boron in high-temperature alloy steel using non-linear inter-element correction and microwave plasma-atomic emission spectrometry

The determination of B in high-temperature alloy steel using microwave plasma-atomic emission spectrometry (MP-AES) is presented. This instrumental emission technique was developed recently using 2.45 GHz microwaves to generate atmospheric pressure N2-plasma, self-sustained inside a modified inductively coupled plasma (ICP) torch. The sample introduction to the MP is pneumatic using a conventional concentric nebulizer and a cyclonic spray chamber system. The emission line detection is sequential using a Czerny-Turner monochromator and charge-coupled device (CCD) system. Boron in steel, generally considered an analytically difficult element in a highly impacted matrix, was determined using HNO3–HCl digested steel solutions and 249.773 nm B emission line. Iron spectral interference on this B emission line was corrected using a non-linear inter-element correction (NL-IEC) method. Steel matrix effects on B recovery were attenuated using the method of standard addition. The amount of B in NBS 348a steel is found to be 58 ± 1 mg kg−1 and the certified amount of B is 55 ± 4 mg kg−1.

A simple and demountable capillary microflow nebulizer with a tapered tip for inductively coupled plasma mass spectrometry

A simple and demountable capillary microflow nebulizer (d-CMN) was developed for inductively coupled plasma mass spectrometry (ICP-MS). It consisted of a nebulizer body, a fused-silica capillary with a tapered tip and a polytetrafluoroethylene (PTFE) adapter. The gas orifice i.d., the solution capillary tip i.d. and its wall thickness were 200, 30, and 5μm, respectively. The sensitivities, detection limits, precisions and the long-term stability with the d-CMN were evaluated. The experimental results indicated that its performances at low uptake rates were similar or better than those obtained with the conventional concentric nebulizer at 820μL/min and the micromist nebulizer at 200μL/min. The demountable construction of the d-CMN permitted that the blocked or broken solution capillary could be conveniently renewed. The low self-aspiration rate (4.77μL/min) and the analytical characteristics comparable to commercial microflow nebulizers made the d-CMN a good choice for coupling capillary electrophoresis and microbore high-performance liquid chromatograph to ICP-MS. The proposed d-CMN was successfully applied in the iodine speciation by coupling microchip capillary electrophoresis (MCE) to ICP-MS. The absolute detection limits for iodide and iodate of 0.20 and 0.29fg were achieved with satisfactory resolution.

UV/spray chamber for generation of volatile photo-induced products having enhanced sample introduction efficiency

A combined spray chamber/UV photolysis unit is described which is shown to substantially enhance sample introduction efficiency for several elements in the presence of 1–5% concentrations of formic, acetic and propionic acids. Enhancement factors of 2–40-fold were achieved for Ag, As, Se, Sb, Hg, I, Bi, Pb and Sn when the aerosol field within the cyclonic chamber produced during conventional concentric nebulizer sample introduction was illuminated by an axially placed 6 W mercury pen lamp. UV photolysis of the organic acids likely initiates radical reactions, generating volatile analyte species.

Study on solvent-loading effect on inductively coupled plasma and microwave-induced plasma sources with a microliter nebulizer

To investigate the solvent-loading effect, a microliter nebulizer, called a sonic spray nebulizer (SSN), was used to introduce a sample solution at the microliter per minute level into an inductively coupled plasma (ICP) and into a nitrogen microwave-induced plasma (MIP). We compared the ICP to the MIP, and the SSN to a conventional concentric nebulizer (CCN). Our results confirm that a certain amount of water solvent is useful for analyte excitation in an Ar-ICP, since hydrogen released from the water enhances the energy transfer inside the plasma. However, we found the dominant water–solvent effect in the N 2-MIP source was to consume MIP energy, rather than to promote the analyte excitation. Therefore, a means of solvent removal should be used with a N 2-MIP. We also discuss other differences between the ICP and the MIP. With the SSN, several organic solvents were successfully introduced into the ICP without degrading the plasma stability.

A multimicrospray nebulizer for microwave-induced plasma mass spectrometry

We have developed a nebulizer, called a multimicrospray nebulizer (MMSN), that efficiently introduces analytes for plasma mass spectrometry and plasma emission spectrometry. In this nebulizer, both the sample solution and the nebulizer gas are divided into several streams to produce a multispray. That is, the MMSN is a nebulizer that contains several micronebulization units, each unit including an orifice for passing the nebulizer gas and a capillary for introducing a sample solution. The microspray from each micronebulization unit can be operated at a microliter per minute sample uptake rate to achieve high nebulization efficiency. The multimicrospray nebulizer is capable of introducing more analyte to the plasma compared with a single-orifice micronebulizer, which has a very low sample uptake rate. In this work, an MMSN with three orifices was found to be suitable for microwave-induced plasma mass spectrometry (MIP-MS). The sample uptake rate can be varied within a range of 5-250 microL/min. Therefore, the nebulizer is unique in its ability to deal with various sample volumes and provide high nebulization efficiency. The sensitivity for all elements obtained with the MMSN was higher than that obtained with a conventional concentric nebulizer (CCN), which is difficult to achieve with other types of microintroduction nebulizers. For most elements, the MIP-MS sensitivity was improved about 2-fold at a sample uptake rate of 150 microL/min, a much lower rate than that for the CCN (usually 0.5-1.5 mL/min). The sensitivity for arsenic was improved by a factor of 5. The relative standard deviation was found to be less than 2.0%.

Speciation of mercury compounds by capillary electrophoresis coupled on-line with quadrupole and double-focusing inductively coupled plasma mass spectrometry

The development and analytical characterization of capillary electrophoresis (CE) coupled on-line with both quadrupole (Q) and double focusing (DF) inductively coupled plasma mass spectrometry (ICP-MS) for the separation and determination of three chemical species of Hg (CH3CH2Hg+, CH3Hg+ and Hg2+) are described. The Hg compounds are separated as mercury–cysteine complexes by capillary zone electrophoresis in a 100 cm × 75 µm id fused silica capillary at 20 kV and using a 20 mM sodium tetraborate decahydrate buffer (pH = 9.3). At relatively high concentrations (parts per million level), the determination of these compounds can be carried out by means of UV detection. However, the determination of low mercury concentrations (parts per billion level) can be achieved only by coupling to ICP-MS detection. To accomplish this coupling a conventional concentric nebulizer has been used. The optimization of the CE-ICP-MS interface operation parameters as well as sample stacking conditions of the analytes are discussed. The analytical performance characteristics of the developed CE-ICP-MS methodology have been evaluated and limits of detection were 4 and 7 µg l−1 (as Hg) for inorganic mercury and methylmercury, respectively. Such low levels for this CE technique are achieved via sample stacking and the use of DF-ICP-MS at low resolution for specific mercury detection.

Sonic Spray Nebulizer for Inductively Coupled Plasma Atomic Emission Spectrometry

A novel nebulizer called a sonic spray nebulizer (SSN) was developed to introduce microliter sample solution for ICP-AES with a high nebulization efficiency. At a sample uptake rate of 50 m l min–1, the detection limit of ICP-AES with the SSN is comparable to that with a conventional concentric nebulizer (CCN) at a typical sample uptake rate of 850 m l min–1. The absolute sensitivity of the SSN was improved by an average factor of 13, compared to that of the CCN. The SSN system is capable of introducing a sample solution at a rate as low as 1 m l min–1 with a relative standard deviation (RSD) of about 2%; therefore, the SSN nebulizer should be very useful for introducing biological or other samples in very limited volumes.

Microliter Sample Introduction Technique for Microwave-Induced Plasma Mass Spectrometry

Nitrogen-MIP-MS has an advantage over conventional inductively coupled plasma mass spectrometry (ICPMS) in that it is free from Ar-related spectral interference when measuring the concentration of elements, for example As and Se. Therefore, MIP-MS is a powerful technique for simultaneous determination of multiple elements. However, the ionization efficiencies in the MIP are lower for elements with high values of ionization potential (IP). Our goal was to improve the sensitivity of MIP-MS for As and Se by optimizing the sample introduction technique. A new nebulizer, called the sonic spray nebulizer (SSN), was developed to introduce a liquid sample into the MIP-MS with a flow rate at the microliter per minute level. Our results showed that plasma characteristics could be significantly affected by the sample introduction method used. Compared with a conventional concentric nebulizer (CCN), the detection limits were improved. By using a sample uptake rate that was only one-seventh of that for the CCN, i.e., a SSN rate of 50 μL/min, detection limits were improved by a factor of about 7 for As, Se, and Au, which have very high IP values. Detection limits were also improved for Te, Be, Zn, Sb, and Cd but remained almost the same for elements with low ionization potentials. A mechanism that accounts for this sensitivity enhancement was discussed. Typically, relative standard deviation was found to be less than 2%. In addition, the formation of oxide ions of rare earth elements was reduced by a factor of more than 100 when the SSN was used. The SSN system is capable of introducing samples at a rate as low as 1 μL/min with good precision, which is highly desirable in many cases.

Characterization of an interface for sample introduction into an inductively coupled plasma

The development of a nebulizer system as an “interface” for inductively coupled plasma spectrometry is described. The interface should make it possible to connect different liquid flow systems to an ICP in an optimal way and consists of a conventional concentric nebulizer, an aerosol chamber with a heating region for desolvation and a jet separator. The working principle of the interface is to attain nearly 100 % conversion of the sample into a dried aerosol in an excess of argon. An acceptable solvent plasma load is obtained by removing the excess argon and the major part of the solvent in the jet separator. The main benefits of the interface are enhanced analyte transport efficiency (≈ 35 %) and enhanced aerosol analyte concentration at acceptable solvent plasma loads.