Number-based Particle Size Distribution Research Articles

Inhibiting the formation of PM0.4 by optimizing the distribution of excess air coefficient in preheating combustion of lignite

Preheating combustion can effectively reduce NOx concentration, but the formation characteristics of PM0.4 in preheating combustion is unclear. In this study, the emission of PM0.4 in preheating combustion was reduced by optimizing the distribution of excess air coefficient. The mass-based particle size distribution (MPSD) of PM10, mass yield of PM0.4, elemental compositions and morphologies of PM, and the number-based particle size distribution (NPSD) were analyzed to discuss the effect of αp on PM formation. The results showed that in preheating combustion, with an increase of αp, the mass yield of PM0.4 first decreased and then increased. The mass yield of PM0.4 is minimum when αp is 0.6. Preheating combustion can simultaneously reduce PM0.4 mass yield and NOx concentration. The relationship between NOx concentration and αp is similar to the relationship between the mass yield of PM0.4 and αp. The MPSD of PM0.4 is multimodal and unimodal when αp is less than 1 and larger than 1, respectively. Particle volume concentration of PM0.4 indicates that the multimodal and unimodal of PM0.4 is a result of evolution of particles with different characteristics of gas-to-particle transformation. The effect of αp on the transformation of inorganic element from coal particles to PM0.4 is S > Fe ≈ Ca ≈ Mg > Na > Si. αp affects the mass yield of PM0.4 by affecting the combustion intensity of coal/char particles in preheating furnace and combustion furnace. When αp is 0.6, the combustion intensity of coal particles in preheating furnace and combustion furnace minimize the vaporization of inorganic elements.

The effect of preheating temperature and combustion temperature on the formation characteristics of PM0.4 from preheating combustion of high-alkali lignite

Preheating combustion is getting popular because it can reduce NOx formation, but its effect on particulate matter (PM) formation is still unclear. This study focuses on the effect of preheating temperature (Tp) and combustion temperature (Tc) on the formation characteristics of fine mode particles (PM0.4) in preheating combustion. The mass-based particle size distribution, elemental compositions and morphologies of PM and number-based particle size distribution were analyzed to reveal the mechanisms of reducing PM0.4 formation during preheating combustion. The results showed that compared with conventional combustion, preheating combustion with optimized Tp and Tc can effectively decrease the mass yield of PM0.4 and NOx concentration by 77.9% − 82.2% and 70.9% − 77.8%, respectively. In preheating combustion, the mass yield of PM0.4 basically didn’t change with Tp. When Tc was lower than Tp, the mass yield of PM0.4 was basically unchanged with Tc. The precursors of PM0.4 mainly vaporized in the preheating furnace. The vaporization of inorganic elements, gas-to-particle transformation, and coagulation occurring in the combustion furnace had a negligible effect on the mass yield of PM0.4. When Tc was higher than Tp, increasing Tc can significantly increase the vaporization of inorganic elements from unburned char/coal particles in the combustion furnace. As a result, the mass yield of PM0.4 increased. To effectively reduce the formation of PM0.4 and NOx, a higher Tp and a lower Tc is suggested. The volatility of inorganic elements in preheating combustion has an order as S > Na > Mg > Fe≈Ca > Si. Refractory elements including Fe, Mg, and Ca contributed the most to decrease of PM0.4 in preheating combustion compared with conventional combustion. Preheating combustion has a stronger reductive atmosphere and a lower particle temperature. The vaporization of inorganic elements from coal particles in preheating combustion is probably determined by particle temperature rather than reductive atmosphere.

Real-Time Nanoparticle Characterization Through Optofluidic Force Induction

We propose and demonstrate a scheme for optical nanoparticle characterization, optofluidic force induction (OF2i), which achieves real-time optical counting with single-particle sensitivity, high throughput, and for particle sizes ranging from tens of nanometers to several micrometers. The particles to be analyzed flow through a microfluidic channel alongside a weakly focused laser vortex beam, which accomplishes two-dimensional trapping of the particles in the transverse directions and size-dependent velocity changes due to the optical forces in the longitudinal direction. Upon monitoring the trajectories and velocity changes of each individually tracked particle, we obtain detailed information about the number-based particle size distribution. A parameter-free model based on Maxwell’s equations and Mie theory is shown to provide very good agreement with the experimental results for standardized particles of spherical shape. Our results prove that OF2i can provide a flexible work bench for numerous pharmaceutical and technological applications, as well as for medical diagnostics.Received 25 April 2022Revised 24 June 2022Accepted 27 June 2022DOI:https://doi.org/10.1103/PhysRevApplied.18.024056© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasClassical opticsLight-matter interactionMetrologyMicrofluidicsOptical forcesPhysical SystemsColloidsNanoparticlesSuspensionsAtomic, Molecular & OpticalCondensed Matter, Materials & Applied PhysicsFluid DynamicsPolymers & Soft Matter

Effect of calcined kaolin on PM0.4 formation from combustion of Zhundong lignite

Kaolin is a widely used additive to alleviate slagging and to control particulate matter (PM) during coal combustion. Calcination is a widely used method of physical modification of kaolin. However, the effect of calcined kaolin on PM during Zhundong lignite combustion is not fully studied. In this research, Zhundong lignite blended with calcined kaolin was combusted in a drop-tube furnace. The performance of calcined kaolin on PM0.4 reduction was analyzed by means of mass-based particle size distribution of PM10, elemental composition of PM0.4, and number-based particle size distribution of PM0.4. Aerosol dynamic modeling was adopted to compare the contribution of chemical adsorption and coagulation to PM0.4 reduction by calcined kaolin. The effect of the addition ratio and the furnace temperature on PM0.4 reduction was systematically investigated. The results showed that the reduction efficiency of PM0.4 by calcined kaolin for Zhundong lignite lacking Si-Al compounds was higher than that for Zhundong lignite rich in Si-Al compounds. Aerosol dynamic modeling indicated that chemical adsorption contributed the most to PM0.4 reduction by calcined kaolin. During Zhundong lignite combustion, the order of the reactivities for the inorganic elements with calcined kaolin was Na > Mg > Fe > Ca. Due to the formation of more reaction sites by calcination, PM0.4 reduction efficiency was proportional to the furnace temperature in range from 900 °C to 1300 °C. By considering the PM0.4 reduction, the increase in SO2 and NOx emissions, and the variation of ash fusion temperatures, the optimized addition ratio of calcined kaolin for Zhundong lignite is approximately 6%.

Study on the formation of ultrafine particulate matter (PM) during char combustion in a wet oxy-combustion atmosphere

In this study, the effect of H2O on the formation of ultrafine particulate matter (PM) in an oxy-combustion atmosphere with various O2 contents of 21%, 27%, and 33% was investigated in a high-temperature drop tube furnace at 1800 K. The combustion-generated ultrafine PM was collected by a 14-stage electrical low-pressure impactor for analyzing the mass- and number-based particle size distribution (PSD). The element composition of ultrafine PM was identified using inductively coupled plasma mass spectrometry. The results indicated that all the primary peaks of the mass- and number-based PSD of ultrafine PM were located nearby 0.2 μm under various O2/CO2/H2O atmospheres. As H2O content increased, both the mass and the number yield of ultrafine PM decreased initially and then increased, with an inflection point at 5% H2O content. The inhibitory effects of 5% H2O content on the formation of ultrafine PM at 21%, 27% and 33% O2 contents were −12.3%, −28.5%, and −33.5%, respectively, while the promoting effects of 30% H2O content were 105.4%, 54.0%, and 7.0%, respectively. Thus, the yield of ultrafine PM in the oxy-combustion atmosphere with low O2 content fluctuates more with the increase of H2O, and was more sensitive to H2O. Moreover, with the increase of H2O and O2 content, the average mass of ultrafine PM exhibited an enlarged tendency. And high H2O content (30%) evidently favored the enrichment of alkali and alkaline earth metals (e.g. Na, K, Ca and Mg), as well as Fe in PM0.1, whereas the volatilization of Si and Al was suppressed.

Characterization of Particle Emissions from a DGEN 380 Small Turbofan Fueled with ATJ Blends

The fine particulate matter (PM) emitted from jet aircraft poses a serious threat to the environment and human health which can be mitigated by using biofuels. This paper aims to quantify PM emissions from a small turbofan fueled with the alcohol to jet (ATJ) synthetic kerosene and its various blends (5%, 20%, and 30% of ATJ) with Jet A-1 fuel. Emissions from a turbofan engine (DGEN 380) with a high bypass ratio, applicable in small private jets, were studied. Among the four fuels tested, the PM-number emission index (EIN) was the lowest for the ATJ 30% blend. EIN for ATJ 30% dropped from 1.1 × 1017 to 4.7 × 1016 particles/kg of fuel. Burning alternative fuel blends reduced the particle mass emissions over the entire range of fuel flow by at least 117 mg/kg of fuel. The particles formed in the nucleation mechanism dominate PM emission, which is characteristic of jet engines. Thus, number-based particle size distributions (PSDs) exhibit a single mode log-normal distribution. The highest values of EIN were found for Jet A-1 neat compared to other fuels. The use of the ATJ additive did not cause significant changes in the size of the particles from nucleation mode. However, a magnitude reduction of nucleation mode was found with the increase in the ATJ ratio.

Titanium dioxide nanoparticles in food: comparison of detection by triple-quadrupole and high-resolution ICP-MS in single-particle mode

We used triple-quadrupole and high-resolution inductively coupled plasma-mass spectrometry (ICP-MS) in single-particle mode to characterize the food additive E171 (titanium dioxide, TiO2) in chewing gum, chocolate candy, and cake decoration in the same sample extracts. Then, we spiked TiO2 particles (with similar characteristics as E171) to milk as an example of a calcium-rich matrix. The obtained particle size distributions with both techniques were highly similar in terms of shape and median and mean diameters. Median diameters were in the range of 123 to 209 nm and mean diameters from 146 to 223 nm. In addition, they were in agreement with results obtained by scanning electron microscopy and asymmetric flow field-flow fractionation coupled to multi-angle light scattering and ICP-MS. Repeatable determination of number-based particle size distributions was possible with both ICP-MS techniques even in a calcium-rich matrix showing that both instruments were similarly efficient in resolving the Ca interferences. The combination of spICP-MS with microscopy and TiO2 recovery allowed validating the methods and identifying the presence of aggregated/agglomerated particles in one sample. For the TiO2 powder and the two remaining food products, recoveries were higher than 60%. Both instruments are fit for purpose even if the analyses were performed with differences in detector mode, dwell times, and calculation tools. This shows that both techniques may be used as long as operating conditions are optimized and applicability range is defined.

Evolution of particulate matter in the post-combustion zone of Zhundong lignite

Understanding the conversion of particulate matter (PM) in the post-combustion zone is important for controlling the emissions and ash deposition from coal combustion. In this study, the evolution of PM in the post-combustion zone of coal was investigated experimentally and numerically. The air combustion of three Zhundong lignite was performed in a drop tube furnace. PM was sampled at different flue gas temperature from 473K to 1273K. Low pressure impactor, X-ray fluorescence, scanning electron microscope, and scanning mobility particle sizer were applied to analyze mass-based particle size distribution (MPSD), elemental compositions, morphology, and number-based particle size distribution (NPSD) of PM. The results show that when the flue gas temperature decreases from 1273K to 473K, the MPSD and compositions of PM0.4-10 remain stable, while PM0.4 moves towards larger particle size. The reduction of NaCl concentration in the flue gas between 1073K and 1273K may be due to the sulfation of NaCl. The critical condensation temperature of NaCl in flue gas is between 843K and 902K. When the flue gas was sampled beyond the critical condensation temperature, NaCl vapors is converted to PM0.4 through nucleation and condensation during the cooling of the sampling system. The particle size distribution of submicron particles in the post-combustion zone is well described by an aerosol dynamics model with moment method. In the post-combustion zone of Zhundong lignite, coagulation is the dominate mechanism controlling the evolution of PM0.4 from 1273K to 473K.

Comparison of Particle Size Distributions of Reference Particles by Using Different Measuring Methods

Particle size analysis is most fundamental analysis to powder technology. However, the validation or calibration of particle size analysis, especially the laser diffraction (LD) method, was not often carried out due to the difficulty to prepare the well-known sample. For example, the validation of LD method need spherical reference particles, of which size distribution is better to have a range over one decade of size. As this request, the Association of Powder Process Industry and Engineering, Japan distributed three kinds of standard reference particles (SRP) of spherical barium titanate glass; their size ranges are 1 – 10 µm, 3 – 30 µm and 10 – 100 µm. Those particles are also fitted to the reference particles in JIS Z 8900-1 Standard.In this paper, the particle size distribution (PSD) based on volume of SRP which was converted from the number-based PSD of SRP measured by a scanning electron microscope (SEM) was compared with PSD measured by LD instruments, which was conducted by the Technical Group of Measurement and Control in APPIE. PSD results measured by LD instruments were almost same as each other. PSD by LD method was slightly different from PSD measured by SEM. This discrepancy was discussed by using by a flow type image analysis method which could measure the size of particles in the aqueous solution. It was found that sample particles could not be dispersed completely in the aqueous solution even if using dispersing instruments such as an ultrasonic bath, and that this influence was not serious to the PSD result when using the suitable operating condition of ultrasonic bath.

Hydroxyapatite/iron oxide nanocomposite prepared by high energy ball milling

Nanocomposites (HAp/iron oxide), made of hydroxyapatite (HAp) and ferrimagnetic iron oxide, were synthesized by high-energy ball milling a mixture consisting of iron oxide nanoparticles and the starting materials used for the HAp synthesis: calcium hydrogen phosphate anhydrous (CaHPO4), and calcium hydroxide (Ca(OH)2). Two HAp/iron oxide samples with the magnetic phase content of 12 and 30 wt.% were prepared and their microstructure, morphology and magnetic properties were analysed by X-ray diffraction and transmission electron microscopy. Furthermore, the measurement of particle size distribution was performed by laser scattering, and temperature/field dependence on magnetization was determined. X-ray diffraction data confirmed the formation of two-phased samples (HAp and spinel iron oxide) without the presence of any other parasite phase. The shape of particles was nearly spherical in both samples, ranging from only a few to several tens of nanometres in diameter. These particles formed agglomerates with the most common value of the number-based particle size distribution of 380 and 310 nm for the sample with 12 and 30wt.% of iron oxide, respectively. Magnetization data showed that both HAp/iron oxide composites had superparamagnetic behaviour at room temperature.

Characterizing particulate matter emissions in an aviation kerosene-fueled model combustor at elevated pressures and temperatures

The present study investigated the characteristics of particulate matter (PM) emissions in a single-dome, Rich-Quench-Lean, model combustor under different operating conditions typical for aero-engines, with special emphasis on identifying the individual effects of pressure, temperature, and equivalence ratio on PM emissions in aero-combustors. Results showed that the number-based particle size distribution was shifted from the nucleation mode (<50 nm) to the accumulation mode (50–1000 nm) as the dome equivalence ratio increased from 0.944 to 1.267. When the dome equivalence ratio further increased from 1.342 to 1.814, the number distribution was shifted to smaller particle sizes that are dominated by the nucleation mode. With the increase of operating pressure, the PM emissions have a notably higher number concentration with smaller size particles. While increasing pressure can significantly enhance the nucleation rate yielding higher primary soot particle concentration, the hydrogen radicals that play a crucial role in the hydrogen-abstraction/carbon-addition soot surface growth mechanism are suppressed, thereby leading to the reduced surface growth rate and smaller particle size. On the other hand, the overall accumulation mode seems not being affected with increasing pressure, resulting in a similar size distribution beyond Dp > 60 nm for the different pressure cases investigated. Regarding the influence of combustion temperature, a non-monotonic response of particle geometric mean diameter with increasing primary zone average temperature was found in that particle size increased and decreased in the temperature range below and above 2270 K respectively. This non-monotonic response with temperature variation is likely caused by the competition between soot growth rate and oxidation rate. It is postulated that the increasing trend of particle size is a result of more carbonaceous particles formed under elevated temperatures providing surface areas available for the condensation of organic compounds, while the soot oxidation rate eventually overtakes at higher temperatures leading to the observed decreasing trend.

Challenges in Determining the Size Distribution of Nanoparticles in Consumer Products by Asymmetric Flow Field-Flow Fractionation Coupled to Inductively Coupled Plasma-Mass Spectrometry: The Example of Al2O3, TiO2, and SiO2 Nanoparticles in Toothpaste

According to the current European regulation on cosmetics, any ingredient present as a nanomaterial should be indicated in the ingredient list. There is a need for analytical methods capable of determining the size of the relevant ingredients and thus assessing if these are nanomaterials or not. An analytical method based on asymmetric flow field-flow fractionation (AF4) and inductively coupled plasma-mass spectrometry (ICP-MS) was developed to determine the size of particles present in a commercial toothpaste. Multi-angle light scattering (MALS) was used for on-line size determination. The number-based particle size distributions (PSDs) of the particles were retrieved upon mathematical conversion of the mass-based PSDs recovered from the AF4-ICP-MS fractograms. AF4-ICP-MS allowed to separate and detect Al2O3 and TiO2 particles in the toothpaste and to retrieve a correct TiO2 number-based PSD. The potential presence of particles in the lower size range of the Al2O3 mass-based PSD had a strong impact on sizing and nanomaterial classification upon conversion. AF4 coupled with ICP-MS and MALS was found to be a powerful approach for characterization of different particles in a multiple-particle system such as toothpaste. Confirmation of particle size by a secondary method such as single particle ICP-MS or hydrodynamic chromatography was crucial.

Conversion of particle size distribution data from mass to number-based and its application to biomass processing

Standard sieving analysis is a simple and common method for determining the mass-based particle size distributions of systems with high polydispersity. Conversion of mass-based particle size distributions to finite number of particles having different sizes (number-based particle size distribution) is required in order to predict the physical characteristics of a polydisperse system or to investigate the behaviour of such a system with computational models that consider the impact of individual particles during large-scale processing. A general method for this conversion from size distribution to number of particles is developed here, that determines the minimal total number of particles that is required for capturing a broad particle size distribution, and identifies the factors that impact the generated mass-based size distribution. As an example, this algorithm is utilised for semi-crystalline biomass particles to demonstrate the effect of different algorithm parameters on the dissolution behaviour of this highly polydisperse system. Both the upper and lower limits of the particle size have an important impact on the physical characteristics of the generated polydisperse system. Considering a low value for the lower limit (minimum particle diameter) causes coarser particles not to be captured well, while considering a very high value for the upper limit results in fine particles not being present in the system. The proposed method and the obtained insights are useful in the numerical non-continuum (discrete) population modelling of polydisperse systems undergoing changes that are physical (e.g., dissolution, drying), chemical (e.g., combustion, gasification), or biological (e.g., enzymatic hydrolysis).

Characterization of bevacizumab by dynamic light scattering while maintaining its native structure.

Bevacizumab, is a humanized monoclonal antibody and patents on Avastin® (Bevacizumab, Roche) will expire in the US in 2019 and in Europe in 2022. Therefore, bevacizumab is a popular target for biosimilar developers. One of the most common problems in the formulation of antibody drugs is protein aggregation. Dynamic light scattering (DLS) is a well-established method for the determination of hydrodynamic dimensions, aggregates, and aggregation points of proteins. In contradistinction to other techniques that require diluted samples or specific conditions, proteins and aggregates can maintain their native structure during DLS measurements. In recent studies, bevacizumab was characterized by DLS using diluted samples. In this study, we aimed at investigating the hydrodynamic dimensions, aggregates, and aggregation onset of bevacizumab (Altuzan®, Turkey, Roche) by DLS, while maintaining its native structure. The intensity, volume, and number-based particle size distribution profiles of the test samples were evaluated and the aggregation onset of the formulation was successfully determined against increasing temperature. It is shown that the preservation of the native structure of commercial formulations in DLS measurements provides an opportunity to the characterization of commercial products and development of biosimilars.

Field flow fractionation techniques to explore the "nano-world".

Field flow fractionation (FFF) techniques are used to successfully characterize several nanomaterials by sizing nano-entities and producing information about the aggregation/agglomeration state of nanoparticles. By coupling FFF techniques to specific detectors, researchers can determine particle-size distributions (PSDs), expressed as mass-based or number-based PSDs. This review considers FFF applications in the food, biomedical, and environmental sectors, mostly drawn from the past 4 y. It thus underlines the prominent role of asymmetrical flow FFF within the FFF family. By concisely comparing FFF techniques with other techniques suitable for sizing nano-objects, the advantages and the disadvantages of these instruments become clear. A consideration of select recent publications illustrates the state of the art of some lesser-known FFF techniques and innovative instrumental set-ups.

Analytical approaches for the characterization and quantification of nanoparticles in food and beverages.

Estimating consumer exposure to nanomaterials (NMs) in food products and predicting their toxicological properties are necessary steps in the assessment of the risks of this technology. To this end, analytical methods have to be available to detect, characterize and quantify NMs in food and materials related to food, e.g. food packaging and biological samples following metabolization of food. The challenge for the analytical sciences is that the characterization of NMs requires chemical as well as physical information. This article offers a comprehensive analysis of methods available for the detection and characterization of NMs in food and related products. Special attention was paid to the crucial role of sample preparation methods since these have been partially neglected in the scientific literature so far. The currently available instrumental methods are grouped as fractionation, counting and ensemble methods, and their advantages and limitations are discussed. We conclude that much progress has been made over the last 5years but that many challenges still exist. Future perspectives and priority research needs are pointed out. Graphical Abstract Two possible analytical strategies for the sizing and quantification of Nanoparticles: Asymmetric Flow Field-Flow Fractionation with multiple detectors (allows the determination of true size and mass-based particle size distribution); Single Particle Inductively Coupled Plasma Mass Spectrometry (allows the determination of a spherical equivalent diameter of the particle and a number-based particle size distribution).

ナノトラッキング法による溶液中のナノ粒子の個数基準計測

Nanoparticle Tracking Analysis （NTA） is known as Particle Tracking Analysis （PTA）. NTA is the methods of focused each particle's Brownian motion analysis using captured video. NTA shows number based particle size distribution with higher resolution than Dynamic Light Scattering （DLS） and particle concentration in the sample. It is summarized the principle of measurement and features in this paper.

Abiotic reversible self-assembly of fulvic and humic acid aggregates in low electrolytic conductivity solutions by dynamic light scattering and zeta potential investigation

The aggregation of humic substances and their interaction with filtration media (membranes, soils) has implications for our understanding of membrane fouling during water treatment, the facilitated transport of contaminants, and the transport of organic matter through the microbial loop. To investigate the aggregation of fulvic and humic acids in low electrolytic conductivity solutions, laboratory studies of simulated environmental water samples as well as actual environmental water samples were examined. Intensity-, volume-, and number-based particle size distributions (PSDs) were obtained by dynamic light scattering. Aggregates were categorized into three ranges, i.e., 10–100nm, 100–1000nm, and >1μm. Individual biomacromolecules and the aggregates between 10nm and 1μm were presumed to be precursors for the formation of a large 5-μm-sized-particle. The self-assembly of the large-in-volume, few-in-number, 5-μm-sized particle was observed in real-time and occurred in unfiltered samples and in samples filtered (0.45μm) at a nominal size one order of magnitude smaller. The supramicrometer-sized particle formed, dissipated, and spontaneously re-formed over turbulent/quiescent cycles in the presence of sodium azide indicating reversible abiotic self-assembly. Zeta potential analyses demonstrated that colloidal stability increased as concentration increased. DLS studies of the environmental water samples were comparable to those of the simulated laboratory samples. The operational range of the instrumentation used in these experiments was 0.6nm–6μm; therefore, aggregates larger than 6μm may exist in these solutions.

Measurement uncertainties of size, shape, and surface measurements using transmission electron microscopy of near-monodisperse, near-spherical nanoparticles

Transmission electron microscopy (TEM) in combination with a systematic selection procedure for unbiased random image collection, semi-automatic image analysis, and data processing has been validated for size, shape, and surface topology measurements of silica nanoparticles. The validation study, assessing the precision and accuracy of the TEM method, consists of series of measurements on two colloidal silica-certified reference materials, with number-based modal area-equivalent circular diameters (ECD) of 19.4 nm (ERM-FD100) and 27.8 nm (ERM-FD304). The measurement uncertainties are estimated for the modal and median particle size, shape, and surface topology parameters of single primary particles. The single primary particles are distinguished from agglomerates using a linear discriminant analysis approach. After optimization of the binning process, the mode associated with the number-based particle size distribution is obtained by lognormal fitting. The methodology described in this paper relies on a high level of automation of calibration, image acquisition, image analysis, and data analysis and gives robust results for the modal ECD. The expanded uncertainty of the modal ECD is estimated to be about 3 %. The largest contribution to the expanded uncertainty stems from the uncertainty associated with the trueness of the TEM method.

Detection and characterization of silver nanoparticles in chicken meat by asymmetric flow field flow fractionation with detection by conventional or single particle ICP-MS

A method of analysis of silver nanoparticles (AgNPs) in chicken meat was developed. The homogenized chicken meat sample, which was spiked with AgNPs, was subjected to enzymolysis by Proteinase K for 40 min at 37 °C. Transmission electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) in single particle mode were used to characterize the number-based size distribution of AgNPs in the meat digestate. Because similar size distributions were found in the meat digestate and in the aqueous suspension of AgNPs used for spiking the meat, it was shown that no detectable dissolution of the AgNPs took place during the sample preparation stage. The digestate was injected into the asymmetric flow field flow fractionation (AF(4)) -ICP-MS system, which enabled fractionation of nanoparticles from the remaining meat matrix, and resulted in one large peak in the fractograms as well as two smaller peaks eluting close to the void volume. The recovery of silver contained in the large AgNP peak was around 80%. Size determination of AgNPs in the meat matrix, based on external size calibration of the AF(4) channel, was hampered by non-ideal (early elution) behavior of the AgNPs. Single particle ICP-MS was applied for determination of the number-based particle size distribution of AgNPs in collected fractions. The presented work describes for the first time the coupling of AF(4) and ICP-MS for AgNP separation in a food matrix.