Nebulizer Gas Flow Rate Research Articles

A new aerosol delivery approach for enhanced long-term respiratory care in resource-poor settings

Continuous aerosol therapy is safe, superior, and the mainstay in the therapy of patients with severe asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), and coronavirus disease (COVID-19). However, continuous nebulization has been perceived as highly expensive and labor-intensive, which often requires specialized medical equipment. Moreover, it is difficult to maintain consistent aerosol output and particle size delivery over an extended period without operator intervention. This work proposes a simple and reliable continuous nebulization method using a conventional gas jet nebulizer and intravenous (IV) bottle/bag. The present work reports detailed experimental studies on a gas jet nebulizer with Particle image velocimetry (PIV), Particle/droplet Imaging Analysis (PDIA), and Mie scattering techniques to demonstrate the feasibility of the proposed technique. The preliminary investigation shows that the proposed method provides continuous liquid output delivery without external supervision. The liquid delivery rate and mass median diameter (MMD) of the nebulizer mainly depend on the gas flow rate and suction height. The MMD of the primary generated droplets is reported to vary between 100 and 230 μm for a ± 10 cm suction height and 500–1000 mlph nebulization gas flow rate. Most importantly, the nebulizer spray angle, stability, droplet size distribution, and the axial and radial velocities of the droplets are marginally affected by the suction height. Therefore, the proposed system is a versatile, safe, and cost-effective method of continuous nebulization therapy, especially in resource-poor countries or contagious disease outbreak situations.

Multi-energy calibration and induced plasma optical emission spectrometry (MEC-MIP OES) as an alternative method for the multi-elemental determination of essential elements in cocoa.

The challenge of combining MEC-MIP OES arises from the limited number of emission lines available in this analytical technique. For the MEC-MIP OES optimization, the emission line wavelengths, sample dilution, proportion sample:standard for preparing MEC solutions, and nebulizer gas flow rate were studied. Then, the use of multi-energy calibration (MEC) and microwave-induced plasma optical emission spectrometry (MIP OES) was proposed as an alternative method for the determination of essential elements (Ca, K, Mg, Mn, and Na) in cocoa. In the optimized conditions, the method presented adequate analytical performance, with recoveries of 94-104% and relative standard deviations lower than 5%, showing adequate precision. The limits of detection (mg kg-1) were 12 for Ca, 2 for K, 3 for Mg, 3 for Mn, and 6 for Na. The proposed method was applied to analyze cocoa samples cultivated in Brazil and Ecuador after acid decomposition. The results were in the range (mg kg-1) of 409-1530 for Ca, 5520-13300 for K, 1460-3210 for Mg, 16-34 for Mn, and 28-61 for Na. Samples cultivated in Ecuador presented higher metal concentrations than the Brazilian samples. The proposed procedure was an easy and reliable approach for determining metals in cocoa samples, enabling multi-elemental determination with a lower cost and simplified calibration to be applied in routine applications.

Microfluidic aerosol-assisted synthesis of gefitinib anticancer drug nanocarrier based on chitosan natural polymer

An aerosol-assisted approach was devised to synthesize gefitinib anticancer drug-loaded chitosan nanocarriers (GefNCs). The nanocarrier synthesis involves mixing and interacting gefitinib molecules with chitosan natural polymer within a microfluidic chip. The combination was nebulized with an on-chip integrated micropneumatic nebulizer with N2 as the nebulizer gas. The aerosol was collected in a beaker containing a glutaraldehyde cross-linking agent while magnetically stirring. The chip was created by CO2 laser engraving on polymethyl methacrylate sheets. The synthesized GefNCs were characterized using FTIR, DLS, FESEM, and TEM. The FESEM images revealed a nanoparticle size distribution of 18.5 ± 4.6 nm. After adjusting numerous experimental parameters such as chip design, polymer concentration, solution flow rate, and nebulizer gas flow rate, the synthesized nanocarrier's release mechanism was investigated using various kinetic models. The results demonstrated that the release behavior of GefNCs is pH-sensitive and greater at acidic pH values than physiological pH, making the synthesized nanocarrier a potential for targeted gefitinib delivery to cancer cells. Furthermore, the kinetic studies revealed that the drug's release mechanism best matches Fick's diffusion rule. Under optimal conditions, the encapsulation efficiency was 77.8 %. The cytotoxicity of the produced nanocarrier was investigated on the A549 non-small cell lung carcinoma. The MTT test revealed that the produced nanocarrier had a lower IC50 than the free medication. Furthermore, cytotoxicity experiments on empty nanocarriers revealed that the materials utilized to synthesize nanocarriers have no appreciable cytotoxicity. The developed microfluidic-assisted approach provides a quicker synthesis procedure with a high encapsulation efficiency.

Development of a Dispersive Liquid-Liquid Aerosol Phase Extraction Method for the Quantification of Ag, Cd, Cu, Ni, and Pb in Seawater by Inductively Coupled Plasma Optical Emission Spectroscopy.

The dispersive liquid-liquid aerosol phase extraction (DLLAPE) method was applied for the determination of Ag, Cd, Cu, Ni, and Pb in seawater samples by inductively coupled plasma optical emission spectroscopy (ICP-OES). Key parameters such as sample pH and extractant concentration were systematically evaluated, with ammonium O,O'-diethyldithiophosphate (DDTP) identified as the optimal chelating agent. Optimal extraction conditions were achieved at pH 2.5 for Ag, Cu, Ni, and Pb, while Cd extraction efficiency was found to be pH independent. The extractant concentration did not greatly improve the extraction efficiency. Furthermore, the influence of nebulizer gas flow rate and extraction time was evaluated, achieving the maximum extraction yield at 0.6 L min-1 and 120 s, respectively. The method was evaluated for accuracy and bias through recovery studies, and the results showed that most elements had recovery rates close to 100% with relative standard deviation values in between 3 and 9%. However, in the case of Ag and Ni, 1.184 and 1.089 correction factors were, respectively, applied to compensate for the bias. Moreover, the procedural limits of quantification (pLOQs) found for Ag, Cd, Cu, Ni, and Pb were 0.4, 0.14, 0.2, 0.2, and 0.2 μg L-1, respectively. The in-house validation of the method provided expanded uncertainty values lower than 6% for all elements except for Ag (16.6%). Finally, the application of the method to real seawater samples from coastal areas in Alicante and San Juan (Spain) confirmed its suitability for trace metal analysis in complex marine matrices, underscoring its potential for environmental monitoring and research.

Microwave-sustained inductively coupled atmospheric-pressure plasma (MICAP) for the elemental analysis of complex matrix samples

Microwave induced plasma optical emission spectrometry (MIP-OES) has gained widespread attention in the last few years for trace elemental analysis. Among the new generation of MIPs it is worth to mention the microwave-sustained inductively coupled atmospheric-pressure plasma (MICAP) for which previous works have shown similar detection capabilities to those afforded by ICP-OES. Nevertheless, this instrument has not been applied yet to complex matrix sample analysis. Therefore, the goal of this work is to evaluate MICAP-OES performance (e.g., analytical figures of merit, matrix effects, etc.) for elemental analysis of samples of different nature (e.g., environmental, food and polymers). To this end, both spectral and non-spectral interferences were investigated for 19 elements (Ag, Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Ni, Pb, Sr, Tl, Zn) in the presence of inorganic acid, organic and saline solutions and compared to a 5 % w w−1 HNO3 solution. Unlike previous MIPs, experimental data showed that the optimum nebulizer gas flow rate for a given emission wavelength was mostly independent of matrix characteristics. Regarding matrix effects, this device was highly robust operating both inorganic acid and organic matrices. Interestingly, when operating saline matrices, changes on emission signal by easily ionizable elements were less significant than those early reported by alternative MIP cavities. Moreover, due to MICAP spectrometer design employed allows real-time simultaneous analysis, Rh, Pd, Sc and Y were suitable internal standards to minimize non-spectral interferences. Finally, MICAP-OES can be successfully applied to the elemental analysis of different complex matrix samples (i.e., CRM-DW1 Drinking water; BCR-146 Sewage sludge industrial; BCR-185 Bovine liver; BCR-278R Mussel tissue; NIST-1549 Non-fat milk powder; ERM-EC681k Polyethylene (high level) and BCR-483 Sewage sludge amended soil).

Characterization of CNC Nanoparticles Prepared via Ultrasonic-Assisted Spray Drying and Their Application in Composite Films.

The ultrasonic-assisted spray dryer, also known as a nano spray dryer and predominantly used on a lab scale in the pharmaceutical and food industries, enables the production of nanometer-sized particles. In this study, the nano spray dryer was applied to cellulosic materials, such as cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). CNC suspensions were successfully dried, while the CNF suspensions could not be dried, attributable to their longer fibril lengths. The nano spray drying process was performed under different drying conditions, including nebulizer hole sizes, solid concentrations, and gas flow rates. It was confirmed that the individual particle size of nano spray-dried CNCs (nano SDCNCs) decreased as the nebulizer hole sizes and solid contents of the suspensions decreased. The production rate of the nano spray dryer increased with higher solid contents and lower gas flow rates. The resulting nano SDCNCs were added to a polyvinyl alcohol (PVA) matrix as a reinforcing material to evaluate their reinforcement behavior in a plastic matrix using solvent casting. After incorporating the 20 wt.% nano SDCNCs into the PVA matrix, the tensile strength and tensile modulus elasticity of the neat PVA nanocomposite film increased by 22% and 32%, respectively, while preserving the transparency of the films.

A new approach for the determination of As, Cu, and Pb in seawater samples using manganese oxide octahedral molecular sieve as a sorbent for dispersive solid-phase microextraction

This study introduces a novel method for preconcentrating As, Cu, and Pb from seawater samples using manganese oxide octahedral molecular sieve (OMS-2), as a sorbent, and the analysis by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The OMS-2 nanomaterial was synthesized and characterized using X-ray diffraction and scanning electron microscopy, revealing a crystallite size of 20.9 nm and a typical needle-like morphology of cryptomelane structure. To optimize the ICP-OES operating conditions and the preconcentration process, a central composite design was used. The optimal conditions for ICP-OES analyses were 1200 W and 0.7 L min−1 for the levels of the radio frequency potential (RF) and nebulization gas flow rate, respectively. The optimal conditions for the adsorption process were achieved at a pH of 6.5, 30 mg of OMS-2, and 35 min of stirring time, in the presence of the sample matrix. The enrichment factors obtained were 66, 45, and 21, and a limit of detection of 0.3, 0.1, and 2.1 μg L−1 for As, Cu, and Pb, respectively. The recovery tests ranged from 80 % to 120 %. The method was successfully applied to determine As, Cu, and Pb in seawater samples.

Analysis of teicoplanin impurities by two-dimensional ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

A two-dimensional ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry （2D-UPLC-Q/TOF-MS） method was established for the separation and structural analysis of the components in teicoplanin. This method effectively solved the problems associated with chromatographic systems， such as liquid chromatography-mass spectrometry （LC-MS）， which used a non-volatile phosphate buffer as the mobile phase and were not suitable for the rapid identification of impurities. Moreover， this method circumvented the complexities associated with locating and identifying impurities using the original method by re-establishing a chromatographic system suitable for LC-MS. In this study， for one-dimensional （1D） chromatography， the chromatographic separation was performed on an Octadecyl silica （ODS） hypersil column （250 mm×4.6 mm， 5 μm） with gradient elution using 3.0 g/L sodium dihydrogen phosphate buffer （pH 6.0）/acetonitrile=9/1 （v/v） as mobile phase A and 3.0 g/L sodium dihydrogen phosphate buffer （pH 6.0）/acetonitrile=3/7 （v/v） as mobile phase B. The column temperature was maintained at 30 ℃ and an ultraviolet detector was used at 254 nm for analysis. For 2D chromatography， desalting was performed on a Waters ACQUITY UPLC BEH C18 column （50 mm×2.1 mm， 1.7 μm） with gradient elution using ammonium formate buffer （pH 6.0） and acetonitrile as the mobile phases. The column temperature was maintained at 45 ℃. The MS data for the components and impurities were collected by positive ion electrospray ionization （ESI） using the full-information tandem MS mode （MSE）. The cone and nebulizer gas flow rates were set at 50 and 900 L/h， respectively. The ion source and nebulizer gas temperatures were set at 120 ℃ and 500 ℃， respectively. The ESI and cone needle voltages were set at 2500 and 60 V， respectively. The collision energy was set at 20-50 eV. The molecular formulas of the components and impurities were determined using their exact masses and isotope distributions， and the structural components and impurities of teicoplanin were deduced from their fragment ions according to the fragmentation pathway of the TA2-2 component. Moreover， the 10 components reported in the European Pharmacopoeia 10.0 were analyzed and 22 impurities of teicoplanin were identified by 2D-UPLC-Q/TOF-MS. Three new impurities and two characteristic fragment ions of the teicoplanin parent nucleus were detected， and the fragmentation pathway of TA2-2 was deduced. Using this method， 1D-UPLC is applicable for the accurate qualification of components based on relative retention times， and 2D-UPLC-Q/TOF-MS is suitable for the rapid identification of the structure of components based on their fragment ions. The results indicate that 2D-UPLC-Q/TOF-MS may be used to analyze the structure of impurities in teicoplanin based on their exact masses， isotope distributions， and fragment ions. The method is rapid， simple， and sensitive， which provides a novel strategy for the quality control and process optimization of teicoplanin.

Characterizing a nitrogen microwave inductively coupled atmospheric-pressure plasma ion source for element mass spectrometry.

A high-power nitrogen-based microwave inductively coupled atmospheric-pressure plasma was coupled to a quadrupole mass spectrometer to investigate its characteristics as an ion source for element mass spectrometry. The influence of operating conditions on analyte sensitivity, plasma background, and polyatomic ion formation was investigated for conventional solution-based analysis. By varying the forward power and the nebulizer gas flow rate, the plasma background ions were found to decrease with increasing gas flow rates and decreasing operating power. Analyte ions showed different trends, which could be related to the physical-chemical properties of the elements. We could identify three groups based on the location of maximum intensity in the power vs. flow rate contour plot. Atomic ions of elements with low first ionization energy and low oxygen bond strength were found to maximize at a high nebulizer gas flow rate and lower microwave power. Elements with intermediate ionization energy and higher oxygen bond strength required higher power settings for optimum sensitivity, while elements with the highest ionization energies required the highest power and lowest gas flow rates for their optimization. The latter group showed a substantial suppression in sensitivity compared to elements of similar mass, which is considered to result from the high abundance of NO in the plasma source, whose ionization energy is close to that of these elements. Metal oxide ions were found at similar or higher abundances than in the conventional argon-based ICP and could be minimized only by using a low gas flow rate and high power settings. These general trends were also observed when the vacuum interface was modified. To change the dynamics of the supersonic expansion, different sampler cone orifice sizes and sampler-skimmer distances were investigated and the interface pressure was lowered through an additional pump. These modifications did not yield significant differences in ion transmission but lowering the interface pressure reduced the relative abundance of metal oxide ions. The limits of detection were evaluated for optimized plasma conditions and found comparable to those of an argon ICP source with the same mass spectrometer.

Optimization of Evaporative Light Scattering Detector using Response Surface Methodology for Liquid Chromatography Analysis of Frondoside A

AbstractResponse surface methodology is employed to investigate the optimum evaporative light scattering detector (ELSD) operating conditions for high performance liquid chromatography (HPLC) analysis of frondoside A, which is a bioactive compound valuable for its anti‐cancer activity. The results suggest that ELSD response is mostly affected by nebulizing gas flow rate and evaporator temperature. The optimum response of frondoside A is achieved by adjusting ELSD evaporator and nebulizer temperature at 80 °C and 35 °C, respectively, with nebulizing gas flow rate of 0.9 SLM. The analysis of variance (ANOVA) test results demonstrated that the established model can successfully describe the relationship between the signal response and ELSD experimental parameters, and predict the optimum ELSD parameters for frondoside A analysis. Furthermore, analytical method validation performed in optimum conditions shows that the proposed method also exhibits adequate sensitivity and linearity, with acceptable precision and accuracy. The results demonstrate the suitability of HPLC‐ELSD technique for the development of routine analysis procedures of frondoside A in natural product samples.

Combination of high performance liquid chromatography and flame atomic absorption spectrophotometry using a novel nebulizer interface supported T shaped slotted quartz tube for the determination of Vitamin B12

A novel nebulizer interface (NI) was proposed to combine high performance liquid chromatography (HPLC) and flame atomic absorption spectrophotometer (FAAS). A glass concentric nebulizer was linked to T-shaped slotted quartz tube (T-SQT) using a tubing to transfer the liquid solution eluted from the chromatographic system into the atomization region of FAAS system. T-SQT was also used to intensify the interaction of atoms with the hollow cathode lamp light. Vitamin B12 was selected as an analyte to show the applicability of the new hyphenated system. After optimizing some parameters such as mobile phase flow rate and pH, nebulizer gas flow rate, T-SQT height and injection volume, linear range for the analyte was determined between 4.7 and 92 mg/kg as Co. Limit of detection (LOD) and limit of quantitation (LOQ) for the HPLC-NI-T-SQT-FAAS system were calculated to be 1.6 and 5.3 mg/kg as Co, respectively. Recovery studies were also conducted to verify the accuracy and applicability of the developed method for vitamin tablets and excellent percent recovery results (~ 100%) with low standard deviation values were obtained when matrix-matching calibration strategy was performed for each vitamin tablet. A successful separation and detection of the analyte was achieved within 3.0 min that offers high sample throughput. Two different vitamin tablets were analyzed by the optimized hyphenated system. The developed method also provides low usage of sample solution in contrast to conventional nebulizer in the FAAS system.

Determination of elemental bioavailability in soils and sediments by microwave induced plasma optical emission spectrometry (MIP-OES): Matrix effects and calibration strategies.

In the past few years, microwave induced plasma optical emission spectrometry (MIP-OES) has generated great interest as an alternative technique to inductively coupled plasma-based techniques due to its lower operational cost. Since MIP-OES suffers from severe matrix effects due to easily ionizable elements (EIEs) (Na, Ca, etc.), it is unclear whether this technique could be employed for elemental bioavailability studies in soils and sediments since the main extractant solutions employed in such works may contain high levels of these elements. Thus, the aim of this work was to evaluate the feasibility of MIP-OES as a detector for such applications. To this end, the influence of different extractant solutions (0.25molL-1 MgCl2, 0.25molL-1 CaCl2, 0.10molL-1 acetic acid, 0.05molL-1 Na2EDTA, 0.25molL-1 NaNO3, 0.25molL-1 NaOAc/HOAc and 0.10molL-1NH2OH·HCl) on the analyte emission of several elements (As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Rh, Se, Sr and Zn) was investigated. Results were compared to those obtained using a reference solution made of 5% w w-1 HNO3 solution. For saline extractant solutions, both the optimum nebulizer gas flow rate (Qg) and analyte emission were modified with regard to the reference solution. In general, the optimum Qg was reduced by between 0.1 and 0.2Lmin-1 for both ionic and atomic lines. Under optimum Qg conditions, analyte emission was supressed by saline solutions except for atomic lines with an upper electronic state below 4eV, which were enhanced. The magnitude of matrix effects was strongly dependent on EIE ionization energy. The lower the ionization energy, the greater the matrix effects were registered. No measurable matrix effects were registered on both Qg and analyte emission within experimental uncertainties for NH2OH·HCl and acetic acid extractant solutions. Experimental data suggest that matrix effects were related to changes in plasma characteristics and the analyte excitation/ionization mechanism. To mitigate matrix effects and improve long-term MIP-OES performance, internal standardization using either Rh (343.489nm and 369.236nm) or OH molecular emission band (308.958nm) was required. This calibration methodology was successfully applied to the study of the elemental bioavailability in soil samples from a vineyard affected by copper-based fungicides and sediment samples from an area affected by mining waste.

Design of experiment-based LC-MS/MS method development for simultaneous estimation of nateglinide and metformin hydrochloride in rat plasma.

This research aims to develop and validate a bioanalytical method for simultaneous estimation of an antidiabetic combination using LC-MS/MS in rat plasma. Nateglinide and metformin hydrochloride are commonly used combination for clinical management of Type 2 diabetes. Hence, simultaneous determination in plasma is essential for the rapid analysis of samples from the pharmacokinetic studies. Statistical optimization was carried out for liquid chromatography (LC) parameters and mass spectroscopic (MS) parameters by design of experiment (DoE) (Design Expert Version 11, Stat Ease Inc., USA) approach. A 33 full factorial design was used for optimization of LC parameters; %methanol, %formic acid, and flow rate were selected as independent variables, whereas peak area and tailing factor were considered as dependent variables for both drugs. Box-Behnken design was used to optimize MS parameters including drying gas flow rate, nebulizing gas flow rate, DL temperature, heat block temperature, and positive voltage as independent factors, and responses selected were [M + H]+ intensity of nateglinide and metformin hydrochloride. The [M + H]+ intensity of the optimized method for nateglinide and metformin hydrochloride were 2,462,838 and 11,873,826, respectively. The model was found significant for optimizing LC and MS parameters with p < 0.05 for both nateglinide and metformin hydrochloride. The optimized method was validated as per the ICH-M10 guideline, which was accurate, precise, and selective. The method was cost-effective and capable of quantitating concentrations in picogram levels for nateglinide and metformin hydrochloride simultaneously.

Signal enhancement in desorption nanoelectrospray ionization by custom-made inlet with pressure regulation.

The efficiency of desorption/ionization becomes more critical as the sampled surface area decreases. Desorption electrospray and desorption nanoelectrospray belong to ambient ionizations and enable direct surface analysis including mass spectrometric imaging. Lateral resolution in tens of micrometers was demonstrated for desorption nanoelectrospray previously, but sensitivity of the surface scan can be an issue. For desorption electrospray, the drag force in the source is driven by the flow of used gases and vacuum suction. Ion signal intensity can be improved by controlling the nebulizing gas flow rate or auxiliary pumping of a closed compartment in front of the mass spectrometer inlet. Because nanoelectrospray generates charged droplets without the assistance of a nebulizing gas, only vacuum suction drives the gas flow. In this study, the effect of pressure drop between the atmospheric and evacuated region of a mass spectrometer on the ion signal intensity was investigated for desorption nanoelectrospray. A modification of the commercial inlet was designed. An auxiliary pump was directly connected to an inner compartment of the modified mass spectrometer inlet through a needle valve that enabled the regulation of the reduced pressure. Adjustment of the pressure drop significantly increased signal intensity (more than one order of magnitude in some cases). To a lesser extent, the temperature of a heated capillary (an integral part of the inlet) also influenced the signal intensity. The applicability of desorption nanoelectrospray equipped with pressure regulation was demonstrated by the analysis of synthetic cathinones or a pill of paracetamol. Because pressure in the inlet depends on the diameters of orifices and the power of vacuum systems of mass spectrometers, the effect of the pressure regulation can be different for different instruments. Nevertheless, the presented results confirmed the importance of pressure drop-driven transport for desorption nanoelectrospray efficiency and can encourage its new applications.

REDUCING THE DETECTION LIMITS OF SPECTROMETER WITH NITROGEN MICROWAVE PLASMA «GRAND-SVCH»

The article presents the results of a study of the effect of the power supplied to the microwave plasma and the nebulizer gas flow rate on the detection limits of the spectrometer with nitrogen microwave plasma «Grand-SVCH». It is shown that a change of the spectral lines intensity of the elements being determined with varying parameters of the spectra excitation source is related to their excitation energy. The maximum intensities of the lines are achieved at a power of 1700 W and a nebulizer gas flow of 0,4 l/min and 0,6 l/min for lines with excitation energies of 4-15 eV and 3,5-4 eV, respectively. Using the obtained values of the parameters of the excitation source of the spectra allows reducing the detection limits of elements by 1,5-4 times.

Green and simple extraction of free seleno-amino acids from powdered and lyophilized milk samples with natural deep eutectic solvents

Natural deep eutectic solvents (NADES) were introduced for the extraction of free seleno-amino acids from lyophilized and powdered milk samples. Different NADES were evaluated, and lactic acid:glucose (LGH) showed the highest selenium recoveries. Selenium analysis was performed by inductively coupled plasma mass spectrometry (ICP MS). Se-NADES analysis in ICP MS was optimized according to the radio frequency power and nebulization gas flow rate. Se-NADES extraction was optimized by an experimental design. LGH dilution, LGH volume, sample quantity, and ultrasound time were factors influencing the extraction. Seleno-amino acids were determined by liquid chromatography-ICP MS. After optimization, the limits of detection obtained were 7.37, 8.63, and 9.64 µg kg−1 for selenocysteine, selenomethionine, and seleno-methyl-selenocysteine, respectively. The NADES-extraction is a green procedure with 2 penalty points in the EcoScale. The method was applied to the analysis of powdered milk, lyophilized Se-fortified sheep milk, and ERM-BD151 skimmed milk powder.

Optimization of Operational Conditions for Scandium Determination in Aluminum Alloys by Inductively Coupled Plasma Optical Emission Spectrometry

A method for the determination of scandium (Sc) in aluminum alloy samples by inductively coupled plasma optical emission spectrometry was developed. The method was optimized by the Box–Behnken design, which evaluated the operational conditions (radio frequency power, nebulizer gas flow rate, and sample flow rate). The optimum conditions were established as a radio frequency power of 1300 W, a nebulizer gas flow rate of 0.83 L/min, and a sample flow rate of 0.9 mL/min. Satisfactory performance characteristics (background equivalent concentration, limits of detection and quantification) were obtained under the optimum conditions. The method proposed using the optimum conditions allowed Sc determination with limits of detection and quantification of 0.15 and 0.48 μg/L, respectively. The accuracy of the proposed method was confirmed by analyzing an aluminum alloy certified reference material and performing a standard addition method. The standard addition experiments resulted in recoveries between 96.5% and 105%. The method developed has been applied to the Sc determination in aluminum alloy samples from the Beijing Institute of Aeronautical Materials, and the recovery study results ranged between 98.0 and 100.5%.

Differential adsorption of analyte and deuterated analogue onto the rotor seal of the injector in high-performance liquid chromatography/electrospray ionisation mass spectrometry.

Samples were injected onto the HPLC system via either a Valco C14W.1 internal sample injector or a Rheodyne 7125 injector, both with dissimilar Vespel rotor seals, and linked to a quadrupole time-of-flight (QTOF) mass spectrometer. Alternatively, samples were infused directly into the mass spectrometer via a syringe-driver. Electrospray ionisation in positive mode was used in both cases. Experiments demonstrated significant differential adsorption of the analyte (RAC inhibitor, NSC23766) and its tri-deuterated internal standard onto the Vespel rotor seal, with the latter seeming to be preferentially adsorbed. The deuterated analogue also showed lower electrospray sensitivity, as demonstrated by syringe infusion of a mixture of the compounds, compared with their separate infusion at the same concentration. This study has demonstrated the problem of differential adsorption onto HPLC Vespel rotor seals, and that the use of a stable-isotope-labelled analogue as internal standard does not guarantee the constancy of the analyte/internal response ratio in quantitative methods. The partial solution was to work at much higher concentration where adsorption, whilst still apparent, was relatively insignificant.

Characterization of matrix effects using an inductively coupled plasma-sector field mass spectrometer

Comprehensive characterization of ICP-SFMS matrix effects as function of analyte mass, matrix mass, focus lens voltage and nebulizer gas flow rate.

Design Characteristics to Eliminate the Need for Parameter Optimization in Nanoflow ESI-MS.

The sampling efficiency in electrospray ionization-mass spectrometry (ESI-MS) can be improved by decreasing the liquid flow rate to the nanoflow regime, where it is possible to draw a large fraction of the ESI plume into the mass spectrometer. This mode of operation is typically more difficult than ESI-MS at higher flow rates because it requires careful optimization of a number of parameters to achieve optimal sampling efficiency. In this work, we screened the relative impact on signal intensity and spray stability of factors that included sprayer position, spray electrode protrusion, sprayer tip shape, spray angle relative to the MS inlet, nebulizer gas flow rate, ESI potential, and means for generating the electric field to initiate electrospray. Based on the screening results, we explore the possibility of providing fixed optimal values for many of the key source parameters to eliminate much of the tuning that is required for conventional nanoflow sources. This approach has potential to greatly simplify nanoflow ESI-MS, while providing optimized sensitivity, stability, and robustness, with decreased variability between analyses.