Charged Aerosol Research Articles

Separation of polyphenols by HILIC methods with diode array detection, charged aerosol detection and mass spectrometry: Application to grapevine extracts rich in stilbenoids

The characterization of plant extracts is usually accomplished by reverse-phase liquid chromatography, but the development of new complementary approaches, such as HILIC, offers an orthogonal method. In this study, five HILIC stationary phases were evaluated to assess their ability to retain polyphenols. They were selected to cover the main different HILIC mechanisms: bare silica; silica with ethylene bridge; neutral amide; amino; zwitterionic. A total of 31 polyphenol standards were used for the screening, including 9 stilbenes, 8 flavonoids, 6 anthocyanins, and 8 phenolic acids. Three different detections were tested: diode array detector, charged aerosol detector and mass spectrometry.Results indicated that silica supports were not suitable for retaining polyphenols, with no or low retention observed except for anthocyanins. The effectiveness of stationary phases in retention of phenolics following the order related to increased retention: zwitterionic, amide, and amino.The choice of mobile phase also influenced retention. Mobile phases containing TFA as pH modifier limited retention, while formic acid was found to be more effective for polyphenol retention. Ammonium buffers also improved retention but often compromised peak shape. pH changes mainly impacted ionizable compounds, such as phenolic acids, by increasing their retention when they were ionized.DAD was wellsuited for detecting polyphenols that possess aromatic rings, though peak wavelengths depend on the structures of the polyphenols. CAD, while less sensitive than DAD and MS, provided an almost similar response for structurally related compounds, even with gradient elution. MS was the preferred detector for quantification when resolution between compounds was challenging, as it is often the case with natural extracts.The study successfully demonstrated that best HILIC conditions were obtained using an amino stationary phase composed of a polyethylenimine and formic acid-based mobile phase. These conditions were successfully applied to the analysis of stilbenoid-rich extracts from different parts of the vine. The elution order of stilbenoids followed the degree of polymerization. With CAD, the chromatographic profile was more representative of sample composition. It was demonstrated for the first time the interest of a combination of HILIC and CAD for analyzing stilbenes, offering a complementary approach to the classic RP analysis.

A simplified tutorial on charged aerosol detection: Understanding the basics, optimization, and troubleshooting

The charged aerosol detector (CAD) measures the overall charge deposited on aerosolized particles to produce a signal proportional to the mass of analyte present, which applies to compounds with or without a chromophore. A significant benefit of CAD is the ability to quantitate a wide range of non-volatile compounds in absence of their authentic standards due to uniform response factor for such analytes. CAD is also a valuable tool to help detect and/or quantitate compounds with poor or no UV absorption. These can include salts, impurities, and a variety of other types of analytes.In this tutorial, fundamental principles of CAD and its utilization, troubleshooting, and maintenance will be demonstrated to ensure proper CAD usage. Successful operation of CAD includes optimizing power function value (PFV) to allow for a broader dynamic range and improve uniformity of response. The use of an inverse gradient (admixed post-column) enables more accurate quantitation, when employing a gradient analysis method. Several troubleshooting strategies, including diagnosing inverse gradient pump organic solvent delivery and determining volume match/mismatch between the inverse gradient and system pumps, will be presented along with important aspects of operating a CAD. Lastly, ensuring reliable results involves monitoring the performance of CAD over time to understand whether it is working sufficiently or if maintenance is required.

Combined Quantification and Characterization of Dissolved Organic Matter by Liquid Chromatography-Mass Spectrometry Using Charged Aerosol Detection.

Dissolved organic matter (DOM) is a complex mixture of thousands of molecular formulas comprised of an unknown number of chemical compounds, the concentration and composition of which are critical to ecosystem function and biogeochemical cycling. Despite its importance, our understanding of the DOM composition is lacking. This is principally due to its molecular complexity, which means that no single method is capable of describing DOM in its entirety. Quantification is typically done by proxy (e.g., relative to carbon content) and does not necessarily match well to compositional data, due to incomplete analytical windows and selectivity of different analytical methods. We present an integrated liquid chromatography (LC)-diode array detector (DAD)-charged aerosol detector (CAD)-mass spectrometry (MS) pipeline designed to both characterize and quantify solid-phase extractable DOM (SPE-DOM) in a single analysis. We applied this method to a set of eight Swedish water bodies sampled in the summer and winter. Chromophoric SPE-DOM was proportionally higher in samples with higher SPE-DOM concentrations but remained relatively consistent between sampling occasions. Ionizable SPE-DOM was relatively consistent across sites but was proportionally higher in summer. Overall, the carbon content of DOM was very consistently ∼40% across sites in both summer and winter. These findings suggest that SPE-DOM concentration at these sites is driven by (presumably allochthonous) chromophoric inputs, with an increased relative contribution in summer of material that is more ionizable and less chromophoric and may be either autochthonous or selectively enriched from allochthonous sources. Thus, with minimal additional effort, this method provided further compositional insights not attained by any single analysis in isolation.

Application of HPLC Coupled with a Charged Aerosol Detector to the Evaluation of Fructose, Glucose, Sucrose, and Inositol Levels in Fruit Juices, Energy Drinks, Sports Drinks, and Soft Drinks

The study aimed to estimate the levels of fructose, glucose, sucrose, and inositol levels in sweetened beverages with a newly developed method using HPLC coupled with a charged aerosol detector (CAD). In total, 85 commercially available non-alcoholic beverages, including 18 energy drinks, 8 sports drinks, 15 soft drinks, 14 fruit drinks, 7 fruit nectars, and 22 fruit juices were analyzed by HPLC-CAD. The method was validated, and it was characterized by a wide concentration range (1–150 µg/mL), sensitivity, and good accuracy (94.9–103%). The results showed significant variation in fructose, glucose, and sucrose concentrations in energy drinks, sports drinks, soft drinks, fruit drinks, fruit nectars, and juice. The highest total sugar contents (fructose, glucose, sucrose, and inositol) were found in energy drinks (14.2 g/100 mL), followed by fruit nectars (13.7 g/100 mL) and soft drinks (12.7 g/100 mL). Statistical analysis (Spearman correlation test, Kruskal–Wallis test) of the data showed significant relationships between particular sugars in the analyzed products.

The Generation of Seismogenic Anomalous Electric Fields in the Lower Atmosphere, and Its Application to Very-High-Frequency and Very-Low-Frequency/Low-Frequency Emissions: A Review

The purpose of this paper is, first of all, to review the previous works on the seismic (or earthquake (EQ)-related) direct current (DC) (or quasi-stationary) electric fields in the lower atmosphere, which is likely to be generated by the conductivity current flowing in the closed atmosphere–ionosphere electric circuit during the preparation phase of an EQ. The current source is electromotive force (EMF) caused by upward convective transport and the gravitational sedimentation of radon and charged aerosols injected into the atmosphere by soil gasses during the course of the intensification of seismic processes. The theoretical calculations predict that pre-EQ DC electric field enhancement in the atmosphere can reach the breakdown value at the altitudes 2–6 km, suggesting the generation of a peculiar seismic-related thundercloud. Then, we propose to apply this theoretical inference to the observational results of seismogenic VHF (very high frequency) and VLF/LF (very low frequency/low frequency) natural radio emissions. The formation of such a peculiar layer initiates numerous chaotic electrical discharges within this region, leading to the generation of VHF electromagnetic radiation. Earlier works on VHF seismogenic radiation performed in Greece have been compared with the theoretical estimates, and showed a good agreement in the frequency range and intensity. The same idea can also be applied, for the first time, to seismogenic VLF/LF lightning discharges, which is completely the same mechanism with conventional cloud-to-ground lightning discharges. In fact, such seismogenic VLF/LF lightning discharges have been observed to appear before an EQ. So, we conclude in this review that both seismogenic VHF radiation and VLF/LF lightning discharges are regarded as indirect evidence of the generation of anomalous electric fields in the lowest atmosphere due to the emanation of radioactive radon and charged aerosols during the preparation phase of EQs. Finally, we have addressed the most fundamental issue of whether VHF and VLF/LF radiation reported in earlier works is either of atmospheric origin (as proposed in this paper) or of lithospheric origin as the result of microfracturing in the EQ fault region, which has long been hypothesized. This paper will raise a question regarding this hypothesis of lithospheric origin by proposing an alternative atmospheric origin outlined in this review. Also, the data on seismogenic electromagnetic radiation and its inference on perturbations in the lower atmosphere will be suggested to be extensively integrated in future lithosphere–atmosphere–ionosphere coupling (LAIC) studies.

Role of the Power Function Value in Linearity and Universality for Charged Aerosol Detectors: Theoretical Elucidations from a Validated Model.

High-throughput drug discovery on the microgram scale is now common, making analyte quantitation without molecule-specific calibration imperative. The charged aerosol detector (CAD) was invented to be a next-generation universal liquid chromatography (LC) detector with excellent response universality for nonvolatile analytes as well as sensitivity for nonchromophoric compounds. Although the CAD is a mass flow-sensitive detector, its response to mass is inherently nonlinear, which challenges traditional quantitation. In CAD software, there is a "power function value" (p) setting that can be used to linearize the signal through digital signal processing. The exact workings of this power function value algorithm remain unknown; however, its optimization is a crucial aspect of analytical method development for LC-CAD. Herein, we developed a theoretical relationship that can be used to predict the chromatogram (plus peak area, width, and height) at any p if the data are collected at p = 1. This model was validated using a diverse dataset comprising 1440 measurements including peak heights, areas, and widths. Predicted areas had an average error of less than 2% showing excellent agreement between calculated and experimental results. An open-access automated code is tested and provided, which predicts the power function value that produces the most linear response. It is vital to note that optimizing the power function value affects peaks of different heights disproportionately. Low-level impurities were shown to be minimized and eventually eliminated by increasing the power function value. This model provides an easy-to-implement tool (MATLAB or Excel) that assists in choosing the optimal p for each LC-CAD method, increasing the speed of method development and improving the accuracy of quantitative workflows.

Release of <sup>137</sup>Cs into the gas phase during the interaction of <sup>137</sup>Cs compounds with molten lead

The release of137Cs into an Ar flowduring the interaction of137CsI and137CsOH—137Cs2CO3with molten lead at a temperature of ~852 Kwas studied.During the heating of Pb0with137CsI,137CsOH—137Cs2CO3, and137CsI—137CsOH—137Cs2CO3, from 2 to 8% of137Cs can pass into the gas flow. Based on the distribution of137Cs between the elements of the gas purification system, it was concluded that the chemical and disperse composition of compounds containing137Cs in the gas phase is quite heterogeneous. Volatile137Cs compounds formed upon heating137CsI,137CsOH—137Cs2CO3, and137CsI—137CsOH—137Cs2CO3with Pb0in a gas flow at ~852 K can contain both charged aerosols and aerosols without electric charge.

RP-CAD for Lipid Quantification: Systematic Method Development and Intensified LNP Process Characterization.

Lipid nanoparticles (LNPs) and their versatile nucleic acid payloads bear great potential as delivery systems. Despite their complex lipid composition, their quality is primarily judged by particle characteristics and nucleic acid encapsulation. In this study, we present a holistic reversed-phase (RP)-charged aerosol detection (CAD)-based method developed for commonly used LNP formulations, allowing for intensified LNP and process characterization. We used an experimental approach for power function value (PFV) optimization termed exploratory calibration, providing a single PFV (1.3) in an appropriate linearity range for all six lipids. Followed by the procedure of method calibration and validation, linearity (10-400 ng, R2 > 0.996), precision, accuracy, and robustness were effectively proven. To complement the commonly determined LNP attributes and to evaluate the process performance across LNP processing, the developed RP-CAD method was applied in a process parameter study varying the total flow rate (TFR) during microfluidic mixing. The RP-CAD method revealed a constant lipid molar ratio across processing but identified deviations in the theoretical lipid content and general lipid loss, which were both, however, entirely TFR-independent. The deviations in lipid content could be successfully traced back to the lipid stock solution preparation. In contrast, the observed lipid loss was attributable to the small-scale dialysis following microfluidic mixing. Overall, this study establishes a foundation for employing RP-CAD for lipid quantification throughout LNP processing, and it highlights the potential to extend its applicability to other LNPs, process parameter studies, or processes such as cross-flow filtration.

Digitally Enabled Generic Analytical Framework Accelerating the Pace of Liquid Chromatography Method Development for Vaccine Adjuvant Formulations.

The growing use of adjuvants in the fast-paced formulation of new vaccines has created an unprecedented need for meaningful analytical assays that deliver reliable quantitative data from complex adjuvant and adjuvant-antigen mixtures. Due to their complex chemical and physical properties, method development for the separation of vaccine adjuvants is considered a highly challenging and laborious task. Reversed-phase liquid chromatography (RPLC) is among the most important tests in the (bio)pharmaceutical industry for release and stability indicating measurements including adjuvant content, identity, and purity profile. However, the time constraints of developing "on-demand" robust quantitative methods prior to each change in formulation can easily lead to sample analysis becoming a bottleneck in vaccine development. Herein, a simple and efficient generic analytical framework capable of chromatographically resolving the most commonly used non-aluminum-based adjuvants across academic and industrial sectors is introduced. This was designed to seek a more proactive approach for fast-paced assay development endeavors that evolved from extensive stationary phase screening in conjunction with multifactorial in silico simulations of adjuvant retention time (RT) as a function of gradient time, temperature, organic modifier blending, and buffer concentration. The multifactorial retention models yield 3D resolution maps with excellent baseline separation of all adjuvants in a single run, which was found to be very accurate, with differences between experimental and simulated retention times of less than 1%. The analytical framework described here also includes the introduction of a more versatile approach to method development by introducing a dynamic RT database for adjuvants covering the entire library of adjuvants with broad mechanisms of action across numerous vaccine formulations with excellent linearity, accuracy, precision, and specificity. The power of this framework was also demonstrated with numerous analytical assays that can be generated rapidly from simulations guiding vaccine processes in the development of new adjuvant formulations. Analytical assay in this work covers content, purity profile by LC with diode array detector (DAD) and charged aerosol detector (CAD), and component identification by LC with mass spectrometry (MS) across complex vaccine formulations, including the use of surfactants (e.g., polysorbates) as well as their separation from adjuvant targets.

Development of a certified reference material for D-phenylalanine with evaluation of enantiomeric purity.

D-Phenylalanine (D-Phe) is a small chiral organic molecule that is both an important pharmaceutical intermediate and used as a calibrator for quantifying amino acids in liquid chromatography-circular dichroism. We have developed a process for a national certified reference material (CRM) for D-Phe following ISO 17034:2016. The identity of D-Phe was confirmed using mass spectrometry (MS) and nuclear magnetic resonance (NMR), infrared, and ultraviolet (UV) spectroscopy. The absolute optical conformation was also determined using circular dichroism (CD) spectroscopy and optical rotation measurements. Impurities were identified via liquid chromatography (LC) with a UV-Vis detector and a charged aerosol detector (CAD) and LC-MS. Both mass balance and quantitative NMR were employed for value assessment, and the associated uncertainty was evaluated. The certified purity was determined to be 0.995 ± 0.003g/g, a validation that was confirmed by CD using L-Phe CRM as a calibrator. Twenty milligrams of raw material was packed in sealed brown glass tubes for storage, and no inhomogeneity was observed. Stability tests revealed that the D-Phe CRM remained stable at -20°C for at least 26months, at 4°C for at least 14days, and at 25°C and 60°C for at least 7days. The D-Phe CRM can be used to ensure the accuracy and reliability of D-Phe quantitation in the pharmaceutical field and also as a calibrator to ensure traceability to the International System of Units (SI) for L-Phe quantitation and protein purity analysis using LC-CD methods. The approach outlined in this paper also has potential for use in the development of other chiral CRMs.

Mass and Mobility of Ions Produced by Radioactive Sources and Corona Discharges.

Positive and negative ions produced by radioactive sources and corona discharges in gases find a number of applications, including charging aerosol particles prior to their measurement by electrical and/or electrical mobility techniques. The degree to which these ions can charge aerosol particles depends on their mobility and mass; properties that are strongly affected by the composition of the carrier gas and the impurities that it contains. We show that when the purity of the carrier gas is increased, the mobility of both positive and negative ions increases by more than 50%, whereas the respective masses reduce by more than 50%. In most cases, the dominant positive species is N4+, whereas NO2- and NO3- prevail for the negative polarity. Differences in ion mobility and mass resulting from the two ionization methods (i.e., radioactive source and corona discharges) remain limited. When volatile methyl siloxanes (VMS) are introduced deliberately to the gas, the mobility of the cations decreases by 39% and their mass increases by 385%, while the dominant mobility and mass peaks of the negative ions remains almost unaffected. Interestingly, introduction of VMS also leads to consistent and reproducible positive ion properties across all variations of the experiments, which can be especially relevant for charging aerosol particles in a reproducible manner. Taken together, the new measurements we report in this paper corroborate prior knowledge that the composition and purity of the carrier gas strongly influence the properties of positive and negative ions generated in aerosol neutralizers, and provide new evidence regarding their evolution in the presence of impurities.

Unified and Versatile Multiplex Platform for Expedited Method Development and Comprehensive Characterization of Therapeutic Peptides.

Agile analytical approaches are needed for fast and comprehensive characterization of peptide drug candidates. In this study, a unified and versatile multiplex platform was developed to expedite method development and enable the routine determination of multiple quality attributes simultaneously. The platform integrates the automation of size exclusion chromatography (SEC), reversed phase liquid chromatography coupled to reversed phase liquid chromatography (RPLC-RPLC), and hydrophilic interaction liquid chromatography hyphenated to charged aerosol detection (HILIC-CAD). Various therapeutic peptide constructs, including macrocyclic peptides and disulfide constrained peptides, across different lots were studied. The effect of the mobile phase acetonitrile content on the impurity profiles was systematically studied using two SEC columns. A prototype MaxPeak Premier SEC 125 Å column packed with BEH PEO particles achieved the separation of impurities (>2.0% area), whereas no impurities could be observed with an ACQUITY UPLC Protein BEH SEC 125 Å column packed with BEH diol particles. Comprehensive impurity profiling and expedited method development was performed utilizing RPLC-RPLC. Each peptide was analyzed by a combination of 12 conditions in the second dimension, using four columns with octadecyl, phenyl-hexyl, and cyano bonded phases, and three mobile phases with various solvents, modifiers, and pH compositions. Additionally, a HILIC-CAD method was developed for the quantification of TFA, commonly present in peptide products.

Electrospray ionisation suppression in aquatic dissolved organic matter studies – Investigation via liquid chromatography–mass spectrometry

Ionisation suppression is a persistent issue in electrospray ionisation mass spectrometry, which decreases the signal of co-eluting analytes. In non-targeted analysis, where analyte and organic matrix identity is unknown, this poses a very challenging analytical problem when it comes to quantitatively assessing differences between samples, including in a compositional sense. In this study, I demonstrate the problems that arise due to ionisation suppression using a very simple sample mixing scheme between a fresh, metabolite rich sample (a leaf leachate) and a forest pond water. Samples were analysed after solid phase extraction on Agilent PPL and using high performance liquid chromatography coupled to electrospray ionisation – Orbitrap mass spectrometry, charged aerosol detector and diode array detector, the latter two allowing quantification of eluting material. I found that more than half of the well-resolved analytes expected to be present (at equal concentration) were completely lost from detection after mixing with pond water DOM. The average recovery of analytical signal (i.e., the signal weighted average), was about 50%, and was highly variable between analytes. Ionisation suppression also affected the signal obtained from the geochemical background DOM, and material recovery decreased slightly when mixing samples and extracting at a higher volume on PPL. Overall, the results showed that ionisation suppression is an extremely important problem for comparison of biogeochemical samples, even when only considering presence and absence of detected features. A multi detector approach and liquid chromatographic separation adds great value in comparison to use of only high resolution mass spectrometry (in direct infusion mode).

Automated multicolumn screening workflow in ultra-high pressure hydrophilic interaction chromatography for streamlined method development of polar analytes

The pharmaceutical industry is rapidly advancing toward new drug modalities, necessitating the development of advanced analytical strategies for effective, meaningful, and reliable assays. Hydrophilic Interaction Chromatography (HILIC) is a powerful technique for the analysis of polar analytes. Despite being a well-established technique, HILIC method development can be laborious owing to the multiple factors that affect the separation mechanism, such as the selection of stationary phase chemistry, mobile phase eluents, and optimization of column equilibration time. Herein, we introduce a new automated multicolumn and multi-eluent screening workflow that streamlines the development of new HILIC assays, circumventing the existing tedious ‘hit-or-miss’ approach. A total of 12 complementary columns packed with sub-2 µm fully porous and 2.7 µm superficially porous particles operated on readily available ultra-high pressure liquid chromatography (UHPLC) instrumentation across a diverse set of commercially available polar stationary phases were investigated. Different mobile phases with pH ranging from pH 3 to 9 were evaluated using different organic modifiers. The gradient and column re-equilibration were judiciously set to ensure a reliable assay screening framework that indicates promising conditions for subsequent method optimization to achieve resolution of challenging mixtures. This UHPLC screening system is coupled with a diode array and charged aerosol detectors (DAD, CAD and mass spectrometry) to ensure versatile detection for a variety of compounds. This fast-screening platform lays the foundation for a convenient generic workflow, accelerating the pace of HILIC method development and transfer across both academic and industrial sectors.

Quantitative analysis of the impurities in Etimicin using hydrophilic interaction liquid chromatography coupled with charged aerosol detector

Etimicin is a typical aminoglycoside antibiotic (AG). High performance liquid chromatography-evaporation light scattering detector (HPLC-ELSD) method is a commonly used method for determining impurities in Etimicin. However, due to the poor reproducibility, low sensitivity and narrow linear range of the ELSD, high-throughput quantitative analysis of impurities in Etimicin currently poses a challenge. In this study, a sensitive method using hydrophilic interaction liquid chromatography coupled with charged aerosol detector (HILIC-CAD) was developed for the analysis of the impurities in Etimicin. The liquid phase conditions for determination impurities in Etimicin were optimized using Box Behnken design (BBD) and response surface methodology (RSM), resulting in satisfactory separation and optimal CAD output signal. We also studied the influence of CAD parameters on the signal-to-noise ratio and linearity of Etimicin and its impurities. This method has also been proven to be effective in separating impurities from two other typical AGs, Isepamicin and Amikacin. In the method validation, the coefficient of determination (R2) of Etimicin, Isepamicin and Amikacin and their impurities were all greater than 0.999, within the range of 0.5–50 μg/mL. The average recoveries of the impurities of three typical AGs were 99.03 %-101.22 %, RSDs all were less than 2.5 % for intra-day and inter-day precision, with good precision and accuracy. The developed HILIC-CAD quantification method was sensitive, accurate and highly selective for quantitative analysis of impurities in the AGs without need ion-pairing reagents, which is ensure the public medication safety. The method is first reported application of HILIC-CAD method for quantitative analysis of the impurities in AGs.

High-Throughput Fluorometric Assay For Quantifying Polysorbate In Biopharmaceutical Products Using Micelle Activated Fluorescence Probe N-Phenyl-1-Naphthylamine.

Polysorbates are among the most used surfactants in biopharmaceutical products containing proteins. Our work aims to develop a high-throughput fluorometric assay to further diversify the analytical toolbox for quantification of PSs. The assay leverages the micelle activated fluorescence signal from N-Phenyl-1-Naphthylamine (NPN). The development and optimization of assay parameters were guided by the pre-defined analytical target profile. Furthermore, NMR was used to probe the interaction between protein, PS80 and NPN in the measurement system and understand protein interference. All assay parameters including excitation and emission wavelengths, standard curve, NPN concentration, and incubation time have been optimized and adapted to a microplate format, making it compatible with automated solutions that will be pursued in the near future to drive consistency and efficiency in our workflows. The specificity, accuracy, and precision of the assay have been demonstrated through a case study. Furthermore, NMR results provided additional insight into the change of the interaction dynamics between PS80 and NPN as the protein concentration increases. The results indicate minimal interaction between the protein and PS80 at lower concentration. However, when the concentration exceeds 75mg/mL, there is a significant interaction between the protein and PS-80 micelle and monomer. A high-throughput fluorometric assay has been developed for quantification of polysorbates in biopharmaceutical samples including in-process samples, drug substance and drug product. The assay reported herein could serve as a powerful analytical tool for polysorbate quantification and control, complementing the widely used liquid chromatography with charged aerosol detection method.

A 3D Numerical Model to Estimate Lightning Types for PyroCb Thundercloud

Pyrocumulonimbus (pyroCb) thunderclouds, produced from extreme bushfires, can initiate frequent cloud-to-ground (CG) lightning strikes containing extended continuing currents. This, in turn, can ignite new spot fires and inflict massive harm on the environment and infrastructures. This study presents a 3D numerical thundercloud model for estimating the lightning of different types and its striking zone for the conceptual tripole thundercloud structure which is theorized to produce the lightning phenomenon in pyroCb storms. More emphasis is given to the lower positive charge layer, and the impacts of strong wind shear are also explored to thoroughly examine various electrical parameters including the longitudinal electric field, electric potential, and surface charge density. The simulation outcomes on pyroCb thunderclouds with a tripole structure confirm the presence of negative longitudinal electric field initiation at the cloud’s lower region. This initiation is accompanied by enhancing the lower positive charge region, resulting in an overall positive electric potential increase. Consequently, negative surface charge density appears underneath the pyroCb thundercloud which has the potential to induce positive (+CG) lightning flashes. With wind shear extension of upper charge layers in pyroCb, the lightning initiation potential becomes negative to reduce the absolute field value and would generate negative (−CG) lightning flashes. A subsequent parametric study is carried out considering a positive correlation between aerosol concentration and charge density to investigate the sensitivity of pyroCb electrification under the influence of high aerosol conditions. The suggested model would establish the basis for identifying the potential area impacted by lightning and could also be expanded to analyze the dangerous conditions that may arise in wind energy farms or power substations in times of severe pyroCb events.

Characterization of ribostamycin and its impurities using a nano-quantity analyte detector: Systematic comparison of performance among three different aerosol detectors

Characterization of aminoglycoside antibiotics like ribostamycin is important due to the complex composition and common toxic impurities. Aerosol detectors are often employed for determination of these non-absorbent analytes. In this work, a robust and cost-effective method was developed for simultaneous detection of ribostamycin and its related substances using high-performance liquid chromatography (HPLC) with a relative new aerosol detector named nano-quantity analyte detector (NQAD). With the introduction of less toxic but more compatible ion-pairs pentafluoropropionic acid (PFPA) and trifluoroacetic acid (TFA) in the eluent, an optimized separation effect was achieved. Compared with the other two aerosol detectors namely ELSD (evaporative light scattering detector) and CAD (charged aerosol detector), method verification and quantitative detection results revealed that NQAD had higher sensitivity than ELSD with a 0.8 μg/mL limit of detection, as well as wider linear range (from 2 μg/mL to 1000 μg/mL) than both CAD (from 2 μg/mL to 200 μg/mL) and ELSD (from 8 μg/mL to 200 μg/mL) detector. The performance of NQAD helped to realize detection of ribostamycin and its impurities with significant concentration differences in a single run. With a cation suppressor to eliminate the ion-suppression caused by the ion-pairs in the eluent, the structure of nine impurities in ribostamycin sample was characterized by liquid chromatography-mass spectrum (LC-MS). Both external standard and area normalization calculation were investigated, and NQAD obtained more accurate results due to its full-range linear response-to-concentration relationship, providing an alternative for routine quality control of multi analyte systems.

Experimental study of aerosol behavior in ambient electric and magnetic fields at low indoor relative humidity

The tendency of aerosols to carry viral particles featured significantly in public discourse during the SARS Covid-19 pandemic. In this research, the potential significance of the aerosol electric charge, especially as it relates to indoor relative humidity (RH) is considered. While electrostatic interactions may occur at any level of humidity, the level of humidity has a strong influence on these interactions. Above 55 % RH, there is sufficient moisture in the air to facilitate neutralization of the electric charges of particles and surfaces, whereas, at lower humidity levels, less moisture and higher surface resistivities enable increasingly stronger electrostatic interactions. Experiments were designed and conducted to study the behavior of electrically charged aerosols in fields emanating from capacitive touchscreens and permanent magnets. These preliminary experimental results suggest that operating indoor environments closer to the 55–60 % RH range could reduce interactions between these charged aerosols and capacitive touchscreens. This relative humidity range is within the acceptable ranges of humidity recommended by ASHRAE standard 55 which defines thermal environmental conditions for human occupancy.

Spontaneous weathering of natural minerals in charged water microdroplets forms nanomaterials.

In this work, we show that particles of common minerals break down spontaneously to form nanoparticles in charged water microdroplets within milliseconds. We transformed micron-sized natural minerals like quartz and ruby into 5- to 10-nanometer particles when integrated into aqueous microdroplets generated via electrospray. We deposited the droplets on a substrate, which allowed nanoparticle characterization. We determined through simulations that quartz undergoes proton-induced slip, especially when reduced in size and exposed to an electric field. This leads to particle scission and the formation of silicate fragments, which we confirmed with mass spectrometry. This rapid weathering process may be important for soil formation, given the prevalence of charged aerosols in the atmosphere.