Conventional Pneumatic Nebulization Research Articles

High-Efficiency Miniaturized Ultrasonic Nebulization Sample Introduction System for Elemental Analysis of Microvolume Biological Samples by Inductively Coupled Plasma Quadrupole Mass Spectrometry

Sensitive and high-throughput analysis of trace elements in volume-limited biological samples is highly desirable for clinical research and health risk assessments. However, the conventional pneumatic nebulization (PN) sample introduction is usually inefficient and not well-suited for this requirement. Herein, a novel high-efficiency (nearly 100% sample introduction efficiency) and low-sample-consumption introduction device was developed and successfully coupled with inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). It consists of a micro-ultrasonic nebulization (MUN) component with an adjustable nebulization rate and a no-waste spray chamber designed based on fluid simulation. The proposed MUN-ICP-QMS could achieve sensitive analysis at a low sampling rate of 10 μL min-1 with an extremely low oxide ratio of 0.25% where the sensitivity is even higher comparing to PN (100 μL min-1). The characterization results indicate that the higher sensitivity of MUN is attributed to the smaller aerosol size, higher aerosol transmission efficiency, and improved ion extraction. In addition, it offers a fast washout (20 s) and reduced sample consumption (as low as 7 μL). The absolute LODs of the studied 26 elements by MUN-ICP-QMS are improved by 1-2 orders of magnitude compared with PN-ICP-QMS. The accuracy of the proposed method was validated by the analysis of human serum, urine, and food-related certified reference materials. Furthermore, preliminary results of serum samples from patients with mental illnesses demonstrated its potential in the field of metallomics.

A chip-based supersonic microfluidic nebulizer for efficient sample introduction into inductively coupled plasma – Mass spectrometry

As the use of microfluidic chips for handling biological samples is increasing, so is the need for combining them with powerful analytical techniques for metal determination such as inductively-coupled plasma mass spectrometry (ICP-MS). So far, coupling a microfluidic chip to an ICP-MS has been demonstrated mainly through the use of conventional pneumatic micro-flow nebulizers. However, disadvantages associated with the use of such nebulizers entail dead volume issues and liquid suction exerted on the outlet channel of the chip. Herein, we propose that a microfluidic chip, bearing a pneumatic nozzle for liquid nebulization, has the potential to advance metal determination in chip-based ICP-MS. More specifically, we demonstrate for the first time that the coupling of a chip-based supersonic microfluidic nebulizer (chip-μf-Neb) to an ICP-MS can be conveniently achieved through the use of a spray chamber with a laminar flow makeup gas. Operation of the combined system was evaluated at low liquid flow rates across 0.5–20 μL min−1, while nebulization and makeup argon (Ar) gas flow rates were optimized with respect to maximizing indium (In) sensitivity and minimizing oxide formation; a maximum sensitivity of 40000 cps (μg L−1)−1 was achieved at 10 μL min−1. The system was further evaluated for its performance in single-particle analysis, featuring a transport efficiency of 46% for Ag nanoparticles. Finally, the capabilities for conducting single-cell analysis were demonstrated with the detection of 80Se and 75As in individual Chlamydomas reinhardtii cells, which were previously incubated in 20 μM of selenate and 300 μM of arsenate, respectively. Efficient operation at low liquid flow rates along with the absence of self-aspiration render this nebulizer a promising tool for combining the powerful field of microfluidics with metal quantitation by means of ICP-MS.

Fast and highly sensitive Cd isotopic analyses in low-Cd complex samples with MC-ICPMS based on plasma electrochemical vapor generation

Cd isotopes have provided a powerful tool for better understanding Cd geochemical cycling in soil, water and biological systems. Conventional solution-based MC-ICPMS techniques used for Cd isotopic analysis typically requires time-consuming purification, which greatly limits the wide application of Cd isotope. In this work, a fast, highly sensitive and cost-effective Cd isotopic analysis method has been developed based on plasma electrochemical vapor generation (PEVG) coupled with MC-ICPMS. PEVG enhances sensitivity by more than 6 times compared with conventional pneumatic nebulization (PN) system, allowing Cd analysis to be carried out with samples as low as ∼ 13 ng. Usefully, the tolerance level for organic resin materials and matrix elements (Sn/In/Pd/Zr/Mo/Zn:Cd > 250:1) is greatly improved because of the excellent matrix separation capability inherent to PEVG. This allows simplification of the complex and time-consuming ion-exchange chromatography purification process, achieving a reduction of time by > 20 times compared to conventional two-step Cd purification process. The precision and accuracy of this method were first assessed by measuring NIST 3108 and BGEG-Cd standard under optimum conditions (δ114/110Cd of 0.00 ± 0.06‰ and −1.00 ± 0.06‰ (2sd, n = 25)). The method was also successfully applied to sensitive and fast determination of δ114/110Cd in various reference materials (soil, sediment, and basalt) and environmental samples (pyrite, galena, sphalerite, soils and tap water), validating the applicability of the proposed technique. Owing to the sensitivity, selectivity, low power, and low gas consumption of the PEVG, the proposed PEVG-MC-ICPMS technique provides a much faster and cost-effective approach for the accurate measurement of Cd isotopic compositions in low-Cd complex samples.

Evaluation of solution anode glow discharge as a vapor generator in ICP-OES procedures: Application to highly sensitive determination of Cd and Hg

Herein, we developed a novel microplasma-assisted vapor generation technique based on solution anode glow discharge (SAGD) as a substitute for the pneumatic nebulization (PN) routinely used in inductively coupled plasma-optical emission spectrometry (ICP-OES). Under the optimal state of the newly proposed SAGD-ICP-OES system, the detection limits (DLs) of Cd and Hg were reduced by some 12- and 90-fold respectively, and an average of 2 times for other elements (Ag, Bi, Pb, Tl and Zn) in comparison with conventional PN. This system not only obtained the good detection limits amenable to the ultra-trace determination of Cd (DL = 0.3 μg L−1) and Hg (DL = 0.2 μg L−1), but also retained the ability of multi-element analysis. Its accuracy was demonstrated by the determination of Cd and Hg using GBW07312 (stream sediments) and GBW10029 (fish) certified reference materials (CRMs) and spiked tap water samples. The results showed good consistency with the certified values and the values obtained using inductively coupled plasma−mass spectrometry.

Determination of trace cadmium in geological samples by membrane desolvation inductively coupled plasma mass spectrometry

The accurate determination of Cd in geological samples by inductively coupled plasma mass spectrometry (ICP-MS) suffers significant interference from polyatomic ions especially the oxides and hydroxides of Mo and Zr. In this study, we coupled membrane desolvation system with ICP-MS to reduce Mo and Zr based interference and accurately measured Cd content in geological samples. With the solvent in samples solution were removed by membrane desolvation system, Zr based interferences were reduced to blank level and Mo based interferences were reduced by about 10 times. In addition, the membrane desolvation sample introduction system also increased the Cd sensitivity 13 times compared to conventional pneumatic nebulizer with spray chamber. Under the optimal conditions, a linear working curve is obtained at least for Cd concentrations of 0.1–10 μg/L, with a correlation coefficient of 0.9999 and detection limit is calculated to be 0.004 μg/L for Cd. The proposed method was demonstrated by analysis of 25 geological standard reference samples and the results showed that membrane desolvation significantly improved analytical accuracy for Cd by ICP-MS, especially for the low Cd samples.

Sensitive determination of Hg together with Mn, Fe, Cu by combined photochemical vapor generation and pneumatic nebulization in the programmable temperature spray chamber and inductively coupled plasma optical emission spectrometry

Continuous photo-induced generation of mercury cold vapor has been successfully coupled with conventional pneumatic nebulization in programmable temperature spray chamber (PCVG–PN–PTSC) allowing fast, sensitive and easy multi-element analysis. The applied technique enabled simultaneous determination of non-volatile forming elements (Fe, Cu, Mn) and volatile Hg, while 15%v/v formic acid is present in the sample. PTSC elevated temperature (40°C) causes partial conversion of sample matrix into vapor form, thus improving plasma robustness. The efficiency of Hg vapor generation and its transport to the plasma is close to 100%. Moreover, spray chamber temperature stabilization improved the precision of the measurements (Hg signal RSD below 0.5%). The achieved limit of detection for Hg (90pgmL−1) at 194.23nm with no monochromator purge is better by almost two orders of magnitude than that obtained by conventional PN-ICP-OES. On the other hand, LODs for non-vapor forming elements are comparable to those obtained with pneumatic nebulization. The linear dynamic ranges for all examined elements are at least three orders of magnitude up to 1000ngmL−1. None mutual interference between examined analytes (Hg, Fe, Cu, Mn) has been observed. The method was validated by the analysis of two CRM materials of different matrix composition (waste water ERM CA713 and estuarine sediment ERM CC580) giving satisfactory results. As low as 2 ppb of Hg can he directly determined in waste water. The proposed procedure uses mild reagents and allows for fast multi-element analysis, and matches green chemistry requirements.

Inductively Coupled Plasma Optical Emission Spectrometry for Rare Earth Elements Analysis

Abstract Inductively coupled plasma optical emission spectrometry (ICP-OES) merits multielements capability, high sensitivity, good reproducibility, low matrix effect and wide dynamic linear range for rare earth elements (REEs) analysis. But the spectral interference in trace REEs analysis by ICP-OES is a serious problem due to the complicated emission spectra of REEs, which demands some correction technology including interference factor method, derivative spectrum, Kalman filtering algorithm and partial least-squares (PLS) method. Matrix-matching calibration, internal standard, correction factor and sample dilution are usually employed to overcome or decrease the matrix effect. Coupled with various sample introduction techniques, the analytical performance of ICP-OES for REEs analysis would be improved. Compared with conventional pneumatic nebulization (PN), acid effect and matrix effect are decreased to some extent in flow injection ICP-OES, with higher tolerable matrix concentration and better reproducibility. By using electrothermal vaporization as sample introduction system, direct analysis of solid samples by ICP-OES is achieved and the vaporization behavior of refractory REEs with high boiling point, which can easily form involatile carbides in the graphite tube, could be improved by using chemical modifier, such as polytetrafluoroethylene and 1-phenyl-3-methyl-4-benzoyl-5-pyrazone. Laser ablation-ICP-OES is suitable for the analysis of both conductive and nonconductive solid samples, with the absolute detection limit of ng-pg level and extremely low sample consumption (0.2 % of that in conventional PN introduction). ICP-OES has been extensively employed for trace REEs analysis in high-purity materials, and environmental and biological samples.

Straightforward way to enhance robustness in ultrasonic nebulization-axial view inductively coupled plasma optical emission spectrometry via an additional N2 gas stream

In the present study a low flow of N2 is mixed with the aerosol produced by ultrasonic nebulization (USN) prior analysis using inductively coupled plasma optical emission spectrometry (ICP OES). The foreign gas is added for improving plasma characteristics in axially-viewed ICP. By computing the Mg ionic to atomic ratio (plasma robustness) it was concluded that N2 dissociates closer to the load coil when USN is used as sample introduction system. The maximum emission intensity of Mg(II) for pneumatic nebulization (PN) was observed at 11mm from the load coil while it was 8mm for USN, indicating earlier aerosol desolvation, atomization and excitation processes in the ICP. Emission profiles of Ar(I) 415.861nm, Ba(II) 486.601nm and Ba(II) 233.527nm indicated that metastable Ar species are overpopulated in the ICP under the N2 flow. Copper and manganese ionic lines with energy close to 16eV (Ar ionization) were monitored to evaluate spatially dependent charge-transfer reaction along the ICP axis in the presence and absence of the N2 flow. The Cu(II) signal profiles indicated abundance of Ar+ species at low distances from the load coil when N2 was added. On the other hand, differences were not observed at longer distances from the load coil for both plasmas (mixed-gas and pure Ar-ICP). The calculated limits of detection (LODs) for both plasmas had the same order of magnitude. Analysis of certified reference samples demonstrated that the accuracy was preserved by adding the low flow of N2. It was concluded that adding a low flow of N2 to the aerosol produced by USN is a simple way to increase plasma robustness, which is usually lower than that achieved using conventional PN.

Effect of temperature on direct chemical vapor generation for plasma optical emission spectrometry: An application of programmable temperature spray chamber

A new approach based on a programmable temperature spray chamber (PTSC) is described that extends the analytical capability of a direct chemical vapor generation technique (DCVG) by affecting the sensitivity of measurements by both microwave induced plasma (MIP) and inductively coupled plasma (ICP) optical emission spectrometry. Examination of DCVG process and instrumental conditions was performed to characterize the new approach when coupled with the robust and non-robust argon ICP, and helium or argon low-power MIP. Hence, a real comparison between four examined plasma spectrometry systems may be attained based on determination of hydride-forming elements including As, Se and Sb, and Hg forming atomic vapor as well as iodine forming molecular vapor. All observed trends are discussed and explained so that the influence of analyte vapor generation process on analytical figures of merit clearly may be distinguished from that of the water aerosol and vapor delivery process.The main advantage of the DCVG system based on PTSC is its full compatibility with conventional pneumatic nebulization system used in plasma spectrometric techniques, and the improvement in determination of elements that are released from aqueous solutions as easily volatile species. In order to improve the sensitivity, the PTSC was either cooled at 0°C in the case of MIP-OES or electrically-heated at 60°C when coupled with the ICP-OES. For ICP-OES, a slight improvement in sensitivity with increasing temperature was observed due to increased sample delivery rate to the plasma rather than that due to increased analyte vapor generation efficiency. With PTSC, the figures of merit by ICP-OES are improved for all analytes studied comparing with those by ICP-OES with a conventional solution nebulization. The LODs obtained for As, Se, Sb, Hg and I were 5, 5.4, 2.7, 0.085 and 9μgL−1, respectively.Concerning DCVG-PN-PTSC-MIP-OES system, a predominant role of the analyte vapor generation efficiency on the analytical performance was found rather than increased analyte transport efficiency. The beneficial effect of the analyte vapor release is enhanced, however, by combination with reduction of the water loading to the plasma by PTSC cooling. The performance of the DCVG-PN-PTSC-He MIP-OES system was evaluated by determining LODs, which are 20, 14, 19, 2.5 and 8μgL−1 for As, Se, Sb, Hg, and I, respectively.

Direct analysis of alcoholic beverages for the determination of cobalt, nickel and tellurium by inductively coupled plasma mass spectrometry following photochemical vapor generation

A novel and sensitive method is described for the determination of Co, Ni and Te in alcoholic beverages by photochemical vapor generation combined with inductively coupled plasma mass spectrometry. Volatile species of Co, Ni and Te were liberated from mixed formic acid and acetic acid media following exposure to a UV source. Limits of quantification of 0.5, 0.1, and 0.4μgL−1 for Co, Ni and Te, respectively, were obtained, which correspond to improvements 9, 35, and 3 times more over those obtained with conventional pneumatic nebulization. Method accuracy was demonstrated by comparison of the determined Co, Ni and Te concentrations with those obtained following sample digestion and determination using conventional solution nebulization for sample introduction, resulting in good agreement at a 95% confidence level.

Towards the use of ICP-OES for the elemental analysis of organic compounds such as glucosamine

Inductively coupled plasma optical emission spectrometry with a long demountable torch (whose outer tube is 2.5 cm longer than a standard torch) and a conventional pneumatic nebulisation system was applied to the determination of C, H and O concentrations from an organic compound dissolved in water. The sample solution was simply aspirated directly into the plasma without any sample pre-treatment (such as desolvation or degassing). The long torch was required to significantly decrease the background arising from entrained air. Good linearity was obtained for C, N, H and O upon calibration with standard solutions prepared from ultrapure tris(hydroxymethyl)aminomethane. A weighed blank correction was applied to compensate for the contribution from water, especially in the cases of H and O. Under these conditions, the detection limits for C, N, H and O were, respectively, 0.2, 50, 1000 and 2000 μmol of analyte per g of solution. Accurate concentrations, according to a Student's t test at the 95% confidence level, were measured for C, H and O in a solution of D-glucosamine hydrochloride. No internal standardisation was necessary. However, the N concentration was biased high, irrespectively of the N emission line used (from 149.262 to 593.178 nm), which rules out spectroscopic interference and will be further investigated. Nonetheless, the possibility of accurately determining C, H and O simultaneously with trace elements makes the approach quite promising. It is much simpler than alternate methods that require derivatisation of the compound prior to detection.

Study of a direct current atmospheric pressure glow discharge in helium with wet aerosol sample introduction systems

In this study a He DC atmospheric pressure glow discharge (APGD) is characterized under dry conditions and with the introduction of wet aerosols. The aerosols are generated by a conventional pneumatic nebulization system using a MicroMist nebulizer placed in a double pass spray chamber according to Scott or alternatively by a custom-built drop-on-demand (DOD) system based on printer cartridges. The experiments are performed at a He gas flow of 500 mL min−1 and 40 mA current. The influences of the H2O load on the discharge rotational temperature (Trot), excitation temperature (Texc) and the electron number density (ne) are determined. Temperature reductions when comparing dry and wet conditions are found to be around 500 K for the Trot and 240–400 K for the Texc. Detection limits for the elements Cd, Cu, Mg, Mn and Na are presented for pneumatic nebulization coupled to a continuous flow injection system. They are found to be between 10 μg L−1 for Na and 140 μg L−1 for Cu. In the case of the drop-on-demand system a value of 16 μg L−1 for Na was obtained. The applicability of the discharge to the determination of Na in a tap water sample at concentration levels of 20 mg L−1 is shown for both introduction systems and the accuracy of the results is found to be within 1.3 mg L−1 as compared to the result of inductively coupled plasma optical emission spectrometry (ICP-OES).

Improved determination of iodine by sequential (photo)chemical vapor generation and pneumatic nebulization in the programmable temperature spray chamber and inductively coupled plasma optical emission spectrometry

Continuous generation of volatile iodine species based on chemical or photochemical oxidation may be further improved using a sequential (photo)chemical vapor generation/pneumatic nebulization/programmable-temperature spray chamber (P)CVG–PN–PTSC system providing the benefits of a temperature-controlled ICP sample introduction technique. Two experimental setups were designed and optimized to obtain the higher sensitivity. In the CVG mode, the sample and the oxidizing solution are continuously pumped and mixed directly before entering a concentric nebulizer placed in the PTSC, while in PCVG mode the sample solution containing 3%v/v acetic acid is on-line exposed to UV radiation before nebulization.A study was conducted to evaluate the performance of a new CVG–PN–PTSC technique for determination of iodine element by ICP-OES. The ICP-OES intensity is enhanced by a factor of up to 12 by prior oxidation of the iodide to volatile species combined with subsequent pneumatic nebulization, presumably because of increased analyte transport efficiency into the plasma. Next, by heating the spray chamber at 40°C, signal intensities were enhanced by a factor of 3 as compared to the results found at room temperature. Furthermore, using an elevated temperature of the spray chamber slightly increased plasma robustness (MgII to MgI line intensity ratio exceeds 10), likely as a result of increased water vapor that improves plasma stability as well as sensitivity. Both systems were optimized in a wide range of chemical and operating parameters.With both CVG and PCVG–PN–PTSC, the slopes of analytical working graphs of ICP-OES are improved by over an order of magnitude for iodine compared to those with a conventional pneumatic nebulization. Generally, for determination of iodine, the technique exhibits a linear dynamic range of 3 orders of magnitude. For iodine, LODs of 11ngmL−1 were achieved in CVG mode and 17ngmL−1 in PCVG mode at 206.15nm. The technique also gave good short-term stabilities below 2% RSD for both modes. Finally, a continuous CVG technique using sodium nitrite exhibits a better analytical performance than the PCVG mode. Quantitative determination of iodide in mineral water is preferentially carried out by the standard addition procedure. The proposed methodologies were validated with determining of trace iodide in simulated seawater in 2% nitric acid standard reference material CRM-SW, giving rise to satisfactory results.

Determination of total mercury in biological tissue by isotope dilution ICPMS after UV photochemical vapor generation

A method is developed for the determination of trace mercury in biological samples using photo chemical vapor generation (PVG) and isotope dilution inductively coupled plasma mass spectrometry (ID ICPMS) detection. Biological tissues were solubilized in formic acid. Subsequently, the sample solutions were exposed to an ultraviolet (UV) source for the reduction of mercury into vapor species prior to ICPMS measurements. The formic acid served not only as a tissue solubilizer in the sample preparation procedure, but also as a photochemical reductant for mercury in the PVG process. The problem arising from the opaque formic acid digested solution was efficiently solved by using ID method. The optimum conditions for sample treatment and PVG were investigated. A limit of detection (LOD) of 0.5 pg g(-1), based on an external calibration, provided 350-fold improvement over that obtained by utilizing conventional pneumatic nebulization sample introduction. Method validation was demonstrated by the determination of total mercury in several biological tissue certified reference materials (CRMs). The results were in good agreement with the certified values.

Advantages and effects of nitrogen doping into the central channel of plasma in axially viewed-inductively coupled plasma optical emission spectrometry

The effects and benefits of N2 addition to the central channel of the ICP through the nebulizer gas used in ICP OES with axial view configuration were investigated in the present study. The N2 flow rate, nebulizer gas flow rate, RF power and sample uptake rate were evaluated and compared for two sample introduction systems (pneumatic nebulization/aerosol desolvation and conventional pneumatic nebulization). It was observed that N2 did not affect solution nebulization and aerosol transport but affects the ICP characteristics. The higher thermal conductivity of N2 (in comparison with Ar) changes energy distribution in the ICP, observed by monitoring the signals of Ar emission lines and sodium emission. The ratio Mg(II)-280.270nm/Mg(I)-285.213nm was utilized as a diagnostic tool for plasma robustness. The addition of N2 (20mLmin−1) increased plasma robustness significantly and mitigated effects caused by Na, K and Ca. For 40 spectral lines evaluated, it was observed that the emission signals of ionic spectral lines were in general more affected by N2 than those of atomic spectral lines. Detection limits, precision, sensitivity and linearity of calibration curves obtained using N2-Ar-ICP were almost similar to those obtained using Ar-ICP. The analysis of 5 different reference materials revealed that accuracy was not degraded by adding N2 to the Ar-ICP.

The influence of the sample introduction system on signals of different tin compounds in inductively coupled plasma-based techniques

The influence of the sample introduction system on the signals obtained with different tin compounds in inductively coupled plasma (ICP) based techniques, i.e., ICP atomic emission spectrometry (ICP–AES) and ICP mass spectrometry (ICP–MS) has been studied. Signals for test solutions prepared from four different tin compounds (i.e., tin tetrachloride, monobutyltin, dibutyltin and di-tert-butyltin) in different solvents (methanol 0.8% (w/w), i-propanol 0.8% (w/w) and various acid matrices) have been measured by ICP–AES and ICP–MS. The results demonstrate a noticeable influence of the volatility of the tin compounds on their signals measured with both techniques. Thus, in agreement with the compound volatility, the highest signals are obtained for tin tetrachloride followed by di-tert-butyltin/monobutyltin and dibutyltin.The sample introduction system exerts an important effect on the amount of solution loading the plasma and, hence, on the relative signals afforded by the tin compounds in ICP–based techniques. Thus, when working with a pneumatic concentric nebulizer, the use of spray chambers affording high solvent transport efficiency to the plasma (such as cyclonic and single pass) or high spray chamber temperatures is recommended to minimize the influence of the tin chemical compound. Nevertheless, even when using the conventional pneumatic nebulizer coupled to the best spray chamber design (i.e., a single pass spray chamber), signals obtained for di-tert-butyltin/monobutyltin and dibutyltin are still around 10% and 30% lower than the corresponding signal for tin tetrachloride, respectively. When operating with a pneumatic microconcentric nebulizer coupled to a 50°C-thermostated cinnabar spray chamber, all studied organotin compounds provided similar emission signals although about 60% lower than those obtained for tin tetrachloride. The use of an ultrasonic nebulizer coupled to a desolvation device provides the largest differences in the emission signals, among all tested systems.

The Role of Nebulized Therapy in the Management of COPD: Evidence and Recommendations

Current guidelines recommend inhalation therapy as the preferred route of drug administration for treating chronic obstructive pulmonary disease (COPD). Previous systematic reviews in COPD patients found similar clinical outcomes for drugs delivered by handheld inhalers - pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs) - and nebulizers, provided the devices were used correctly. However, in routine clinical practice critical errors in using handheld inhalers are highly prevalent and frequently result in inadequate symptom relief. In comparison with pMDIs and DPIs, effective drug delivery with conventional pneumatic nebulizers requires less intensive patient training. Moreover, by design, newer nebulizers are more portable and more efficient than traditional jet nebulizers. The current body of evidence regarding nebulizer use for maintenance therapy in patients with moderate-to-severe COPD, including use during exacerbations, suggests that the efficacy of long-term nebulizer therapy is similar, and in some respects superior, to that with pMDI/DPIs. Therefore, despite several known drawbacks associated with nebulized therapy, we recommend that maintenance therapy with nebulizers should be employed in elderly patients, those with severe disease and frequent exacerbations, and those with physical and/or cognitive limitations. Likewise, financial concerns and individual preferences that lead to better compliance may favor nebulized therapy over other inhalers. For some patients, using both nebulizers and pMDI/DPI may provide the best combination of efficacy and convenience. The impact of maintenance nebulizer treatment on other relevant clinical outcomes in patients with COPD, especially the progressive decline in lung function and frequency of exacerbations, needs further investigation.

Correction of matrix effects for As and Se in ICP OES using a Flow Blurring® multiple nebulizer

A new and efficient multiple nebulizer based on Flow Blurring® hydrodynamics (FBMN) has been employed for elemental analysis. The aerosol generated by the FBMN has been characterized and compared with a conventional pneumatic nebulizer (MicroMist®, MM). Both nebulizers have been operated with the same cyclonic spray chamber for comparison. At a solution flow rate of 300 μL min−1 and a nebulizer gas flow rate of 0.60 L min−1 the aerosol produced by the FBMN is formed by droplets smaller than 53 μm, and the Sauter mean diameter (D3,2) and the median diameter (D50) of the primary aerosols are 16.3 and 16.8 μm, and 20.4 and 23.3 μm with the FBMN and MM, respectively. The sample introduction system based on the FBMN successfully corrects matrix effects in As and Se determination by inductively coupled plasma optical emission spectrometry. The FBMN makes feasible the implementation of an on-line internal standard (I.S.) strategy by mixing the I.S. solution with analytical reference solutions or a sample solution directly in the spray chamber. It has been demonstrated that the combination of FBMN and In as an internal standard leads to better accuracy for determining As in a lake sediment.

Ultrasonic nebulization with an infrared heated pre-evaporation tube for sample introduction in ICP-OES: application to geological and environmental samples

An improved sample introduction system was developed for inductively coupled plasma optical emission spectrometry (ICP-OES). The heater/condenser (HC) of a commercial ultrasonic nebulizer (USN) system was replaced by a pre-evaporation tube (PET) and a sheathing device. The aerosol exiting the USN was heated to 400 °C by infrared (IR) heating. Multivariate optimizations were conducted under robust conditions to find operating conditions improving the detection limit. Under optimum conditions and compared to conventional pneumatic nebulization, 10–25 fold improvement in sensitivity and detection limit was obtained for a range of elements using USN-PET(IR), including elements that are removed in the HC (such as Hg and B) of USN-HC. Compared to USN-PET where the PET is heated with heating tape, and to conventional USN-HC, USN-PET(IR) provided a two-fold improvement in sensitivity and detection limit. The improvement was more significant for ionic emission lines than atomic emission lines. Plasma robustness, measured by the Mg II/Mg I intensity ratio, also increased significantly, enabling the accurate multi-element analysis of geological and environmental samples using an external calibration, with an Ar emission line for internal standardization. Moreover, compared to an identical USN-PET set-up operated with the same aerosol carrier gas flow rate, but with heating tape, USN-PET(IR) significantly reduced the washout time during the analysis of geological materials, making it essentially independent of the element (with the possible exception of Hg) and analyte concentration (at least up to 400 mg L−1), which suggests that it now mostly arises from the dead volume of this sample introduction system.

Selective identification, characterization and determination of dissolved silver(i) and silver nanoparticles based on single particle detection by inductively coupled plasma mass spectrometry

The different behaviours of dissolved silver and silver nanoparticles under ICP-MS single particle detection conditions have been used to differentiate directly between both forms of silver in aqueous samples. Suspensions containing silver nanoparticles at number concentrations below 109 L−1 and/or dissolved Ag(I) are introduced into the ICP-MS by conventional pneumatic nebulization and measured with a time resolution of 5 ms. Each silver nanoparticle is converted in the ICP into a packet of ions, which are detected as a single pulse, whose intensity is proportional to the number of silver atoms in the nanoparticle, whereas dissolved silver produces pulses of averaged constant intensity. The frequency plots with respect to the intensity measured for each pulse show independent distributions for dissolved silver and silver nanoparticles, whose profiles are also different (Poisson and lognormal, respectively). Size limits of detection for pure Ag nanoparticles of 18 nm, equivalent to a silver mass of 32 ag, were obtained. Number concentration limits of detection of 1 × 104 L−1 can be achieved. A methodological approach for identification, characterization and determination of mass and number concentration of dissolved Ag(I) and silver nanoparticles at environmentally relevant concentrations is presented.