Μm Particles Research Articles

Overcoming the Strong Sample Solvent Effect for Sustainability Measurement Challenges in Liquid Chromatography. Example for Bisphenol-A.

This paper describes an approach to achieve low parts per billion (ppb) concentration level detection using a reversed-phase ultrahigh-performance liquid chromatographic ultraviolet absorbance detection method with large-volume feed injection (FI) for analytes in dichloromethane (DCM). FI is a novel technology that allows sample injection at a defined speed into the LC mobile phase. We demonstrate this approach for a mixture of bisphenol A and its diglycidyl ether derivatives in DCM. DCM is a very strong injection solvent at reversed-phase LC conditions and is typically immiscible with a starting reversed-phase gradient mobile phase containing a high percentage of water. As a result, reduced separation performance and even peak splitting are seen with classic flow-through injection. The method setup comprised an octyl-bonded core-shell stationary phase (150 × 4.6 mm i.d., 2.7 μm particle size) with a water/acetonitrile mobile phase gradient and an exceptionally high injection volume of 45 μL of DCM solution using FI. Optimization of feed speed (1%) and isocratic hold duration (4 min) was crucial for final separation conditions. FI delivered more than a 20-fold improvement in the limit of detection (LOD) compared to standard flow-through injection while maintaining peak resolution. The LOD of the final method ranged between 1 and 10 ppb in the polymer resin. This methodology has high potential for trace analysis in a large variety of applications that suffer from the "strong solvent effect".

Loading Dyes into Chiral Cd/Zn-Metal-Organic Frameworks for Efficient Full-Color Circularly Polarized Luminescence.

Host-guest chemistry of chiral metal-organic frameworks (MOFs) has endowed them with circularly polarized luminescence (CPL), it is still limited for MOFs to systematically tune full-color CPL emissions and sizes. This work directionally assembles the chiral ligands, metal sites and organic dyes to prepare a series of crystalline enantiomeric D/L-Cd/Zn-n MOFs (n=1~5, representing the adding amount of dyes), where D/L-Cd/Zn with the formula of Cd2(D/L-Cam)2(TPyPE) and Zn2(D/L-Cam)2(TPyPE) (D/L-Cam=D/L-camphoric acid, TPyPE=4,4',4'',4'''-(1,2-henediidenetetra-4,1-phenylene)tetrakis[pyridine]) were used as the chiral platforms. The framework-dye-enabled emission and through-space chirality transfer facilitate D/L-Cd/Zn-n bright full-color CPL activity. The ideal yellow CPL of D-Cd-5 and D-Zn-4, with |glum| as 4.9 × 10-3 and 1.3×10-3 and relatively high photoluminescence quantum yield of 40.79 % and 45.40 %, are further assembled into a white CPL light-emitting diode. The crystal sizes of D/L-Cd/Zn-n were found to be strongly correlated to the types and additional amounts of organic dyes, that the positive organic dyes allow for the preparation of > 7 mm bulks and negative dyes account for sub-20 μm particles. This work opens a new avenue to fabricate full-color emissive CPL composites and provides a potentially universal method for controlling the size of optical platforms.

Microplastics release from infant feeding bottles and milk storage bags

The health impairment of microplastics (MPs) in infants has received considerable attention, with oral ingestion being an important exposure route. However, research remains limited on MPs released in feeding bottles (FBs) and breastmilk storage bottles (BSBs) during daily use. To address this gap, our study investigated the MPs released from polyphenylene sulfone resins (PPSU)-FBs, silicone-FBs, polyethylene (PE)-BSBs, and low-density polyethylene (LDPE)-BSBs under typical usage conditions. Our findings revealed that the four materials of FBs and BSBs can release 1465–5893 particles/L MPs (median concentration). The predominant MPs released from all FBs and PE-BSBs were identified as PE, while LDPE-BSBs predominantly released polyethylene terephthalate (PET) and acrylates (ACR). Approximately 70% of MPs were found within the 20–50 μm particle size range. Higher temperatures led to a two-fold increase in the total MPs. Notably, infants would additionally intake 2080–5910 MPs per day through FBs and BSBs. Months with higher nutritional requirements, and when using silicone FBs and LDPE BSBs, increased the ingestion of MPs in infants. In conclusion, our study highlighted that those FBs and BSBs can precipitate varying numbers, types, and particle sizes of MPs. To protect infants from MPs ingestion, it is recommended to choose non-plastic FBs and non-plastic breastmilk storage containers.

The Influence of Preablation Embolization Particle Size on the Size of the Microwave Ablation Zone in a Porcine Orthotopic Renal Tumor Model

PurposeTo combine arterial embolization with different embolic agents, followed by microwave ablation (MWA) in a porcine renal tumor (RT), to evaluate the ideal setting to produce the largest change in the size of the ablation zones (AZs). Materials and MethodsIn a transgenic porcine kidney, 32 sites were inoculation with 28 orthotopic RT produced. Experimental groups (23 tumors) underwent angiography with intra-arterial embolization using various embolic materials (calibrated particles from 40 to 1,200 μm and ethiodized oil) to achieve vascular stasis of the RT. MWA using a standard protocol (3 minutes at 65 W) was subsequently performed for all tumors. Next, a gross and histologic ex vivo analysis of the AZ was performed. ResultsControl group AZ volume without prior embolization was 5.24 cm3 (SD ± 0.55). AZs after embolization with 40 μm, 100 μm, 300–500 μm, 900–1,200 μm particles were significantly larger than those with MWA alone (mean, 15.39 cm3 [SD ± 4.54]; P = .002; 11.07 cm3 [SD ± 1.39]; P = .001; 8.68 cm3 [SD ± 0.77]; P = .001; and 9.90 cm3 [SD ± 1.62]; P = .002, respectively). Liquid embolic ethiodized oil emulsion did not create a significant increase in the AZ (5.92 cm3 [SD ± 1.43 cm3]; P = .492). ConclusionsPre-MWA arterial embolization in a porcine RT model produced a statistically significant increase in the AZ when compared with MWA alone. Using smaller particle size embolic material with distal embolization at the tumor arterioles (50–150 μm) produced the largest, almost 3-fold increase in AZ volume.

Simultaneous Estimation of Atazanavir & Ritonavir in API & Marketed Formulations by Using RP-HPLC

Development and validation of RP-HPLC method for simultaneous estimation of Atazanavir and Ritonavir in their combined tablet dosage form. Atazanavir and Ritonavir are antiviral agents used in treatment of HIV. A simple, precise, rapid, accurate and cost-effective high- performance liquid chromatography (HPLC) method was successfully developed and validated for simultaneous estimation of Atazanavir and Ritonavir in their combined tablet dosage form. The selected mobile phase was Methanol: Phosphate Buffer in proportion 65:35 v/v respectively. The optimized columns used are C18 column, Symmetry and Zodiac column. X bridge C18 (4.6×150 mm, 5 µm) particle size was found to be ideal as it gave good peak shape and resolution at 1ml/min flow for Atazanavir and Ritonavir. In this study, the validation of Atazanavir and Ritonavir in API and marketed formulations were performed keeping in accordance with the parameters like system suitability, specificity, linearity, accuracy, precision (reproducibility & repeatability), robustness. The developed stability indicating method is capable for determination of impurities of Atazanavir and Ritonavir in combined tablet dosage form as well as individual dosage forms also. The method has been successfully validated according to ICH guidelines and the results obtained by using RP – HPLC are rapid, accurate and precise. The proposed methods were successfully applied for the analysis of synthetic mixtures and pharmaceutical formulations of Atazanavir and Ritonavir.

Parallelization of Curved Inertial Microfluidic Channels to Increase the Throughput of Simultaneous Microparticle Separation and Washing

The rising global need for clean water highlights the importance of efficient sample preparation methods to separate and wash various contaminants such as microparticles. Microfluidic methods for these purposes have emerged but they mostly deliver either separation or washing, with very low throughputs. Here, we investigate parallelization of a curved-channel particle separation and washing device in order to increase its throughput for sample preparation. A curved microchannel applies inertial forces to focus larger 10 µm microparticles at the inner wall of the channel and separate them from smaller 5 µm microparticles at the outer wall. At the same time, Dean flow recirculation is used to exchange the carrier solution of the large microparticles to a clean buffer (washing). We increased the number of curved channels in a stepwise manner from two to four to eight channels in two different arraying designs, i.e., rectangular and polar arrays. We examined efficient separation of target 10 µm particles from 5 µm particles, while transferring the larger microparticles into a clean buffer. Dean flow recirculation studies demonstrated that the rectangular arrayed device performs better, providing solution exchange efficiencies of more than 96% on average as compared to 89% for the polar array device. Our 8-curve rectangular array device provided a particle separation efficiency of 98.93 ± 0.91%, while maintaining a sample purity of 92.83 ± 1.47% at a high working flow rate of 12.8 mL/min. Moreover, the target particles were transferred into a clean buffer with a solution exchange efficiency of 96.81 ± 0.54% in our 8-curve device. Compared to the literature, our in-plane parallelization design of curved microchannels resulted in a 13-fold increase in the working flow rate of the setup while maintaining a very high performance in particle separation and washing. Our microfluidic device offers the potential to enhance the throughput and the separation and washing efficiencies in applications for biological and environmental samples.

Inhaled corticosteroid delivery is markedly affected by breathing pattern and valved holding chamber model.

There is a scarcity of high-quality research on the efficient delivery of inhaled corticosteroids using valved holding chambers (VHCs) in children. The delivered dose (DD) of fluticasone from a metered dose inhaler (pMDI) was tested using four VHCs: AeroChamber plus Flow-Vu (AC), Babyhaler (BH), EasyChamber (EC), and Optichamber Diamond (OD). The in vitro setup included an anatomical child throat model, Next Generation Impactor, and a breathing simulator to generate tidal breathing of a four and a 6-year-old child, and adult type single inhalation. OD showed the lowest proportion of fluticasone trapped in the throat with all breathing patterns. AC showed similar fine particle dose (FPD) in the respirable range (1-5 µm) irrespective of the breathing pattern. For BH, the median FPD 1-5 µm was highest during adult breathing. OD and EC showed higher overall DD and higher doses in the 1-5 µm range with paediatric breathing profiles compared to adult inhalation. The median DD and FPD 1-5 µm were significantly lower with BH compared to any other VHCs during tidal breathing. Compared to EC, the FPD of the other VHCs were skewed towards <2 µm particles. Fluticasone delivery is markedly affected by breathing pattern and VHC model. The observed differences in throat deposition and FPD delivered may have significant clinical implications for side effects and controlling airway inflammation. All VHCs intended for paediatric use should undergo testing using internationally recognised standardised methods incorporating clinically relevant paediatric breathing patterns.

Particle Shape-Based Evaluation of the Leaching of Sphalerite Ore in Dilute Acid Solutions

In this study, the effects of changes in particle shapes on dissolution efficiencies in zinc (Zn) recovery from a lead-zinc (Pb-Zn) ore by acid leaching method were investigated. In the experiments with nitric acid (HNO3), sulfuric acid (H2SO4), and hydrochloric acid (HCl), particle size (75-106-150 µm), solids ratio (5-10-15-20-25%), leaching time (30-60-120-180-240 min), acid dosage (0.25-0.5-1-2-5 M) and pulp temperature (30-40-50-60-70 oC) parameters were analyzed. Optimum results were obtained under the conditions of 75 µm particle size, 15% solids ratio, 120 min leaching time, 0.5 M acid dosage, and 50°C pulp temperature for H2SO4; 106 µm particle size, 25% solids ratio, 60 min leaching time, 0.5 M acid dosage, and 70°C pulp temperature for HCl; 75 µm particle size, 20% solids ratio, 60 min leaching time, 1 M acid dosage, and 50°C pulp temperature for HNO3. As a consequence of the tests performed under these optimized conditions, 97.32%, 96.38% and 96.06% Zn dissolution efficiencies were obtained. Within the context of particle shape factor research, microscope images of the leaching residues were obtained from the experiments in which the pulp temperature, acid dosage, and leaching time parameters were examined. The samples obtained from the experiments with all three acids were compared with the ore samples, and the impacts of changes in circularity, roundness, and solidity values on dissolution efficiencies were interpreted.

Multifunctional air filter with enhanced filtration, formaldehyde degradation, and antibacterial properties using PET, PDA, and RGO-TiO2

Currently, most air filters, such as polyester (PET) fiber non-woven fabric, only have a single function of particulate filtration. However, the removal of substances harmful to human health, such as volatile organic compounds (VOCs) and bacteria, is becoming increasingly important in indoor air purification. Herein, based on the biomimetic surface functionalization properties of polydopamine (PDA) and the photocatalytic degradation of organic matter and the antibacterial effect of RGO (reduced graphene oxide)-TiO2, a multifunctional NWP2/PET-PDA-RGO-TiO2(P/PPRT) filter with a sandwich structure was prepared for formaldehyde degradation, aerosol filtration, and bactericidal operation. The P/PP2R0.05T20 maintains optimal performance of photocatalytic reaction kinetics and reaches a formaldehyde degradation rate of higher than 79 % within 300 min in the 7th cycle of usage. Compared with the base subtracts, P/PP2R0.05T20 has the highest filtration efficiency of 88.57–99.18 % for 0.3–10 µm particles, respectively, and has a filtration efficiency of higher than 74 % for 0.3 µm particles in the 7th cycles of usage. The quality factor of P/PP2R0.05T20 is improved significantly due to the sandwich structure. The effect of loaded particulate on the catalyst for photocatalytic degradation of formaldehyde was also studied. It was found that the photocatalytic formaldehyde degradation rate of P/PP2R0.05T20 is about 81.8 % within 300 min under different A2 particulate load content. In addition, P/PP2R0.05T20 has a bioaerosol removal rate of higher than 98 % against E. coli. This study provides a practical approach to preparing a multifunctional air filter with the performance of aerosol filtration, photocatalytic degradation of formaldehyde, and bactericidal function using PET non-woven fabric.

Characterization of pediatric extrathoracic aerosol deposition with air-jet dry powder inhalers

The use of air-jet dry powder inhalers (DPIs) offers a number of advantages for the administration of pharmaceutical aerosols, including the ability to achieve highly efficient and potentially targeted aerosol delivery to the lungs of children using the oral or trans-nasal routes of administration. To better plan targeted lung delivery of pharmaceutical aerosols with these inhalers, more information is needed on the extrathoracic (ET) depositional loss in pediatric subjects when using relatively small (e.g., 0.5–2 μm) particles and including oral or nasal device interfaces. The objective of this study was to implement validated computational fluid dynamics (CFD) models to characterize ET depositional loss during mouth-throat (MT) and nose-throat (NT) aerosol administration to pediatric subjects (2–10 years old) using an air-jet DPI platform across a range of initial small-particle aerosol sizes (0.41–13.65 μm) and inhalation flow rates (8–20 L/min).A new CFD model focused on small-particle aerosol depositional loss in existing pediatric airway models was developed and validated with existing in vitro data. The validated CFD model was then used to characterize depositional loss in the MT and NT regions of children using particle sizes, flow rates and interfaces consistent with air-jet DPIs.Successful validation of the CFD model for small-particle aerosol deposition was achieved through enhanced resolution of the near-wall transport conditions. Existing non-dimensional parameters were used to produce high quality single-curve deposition efficiency correlations with r2 values in the range of 0.95–0.97. A new method for predicting realistic polydisperse aerosol deposition using the developed correlations and an equivalent monodisperse particle diameter was also introduced. In conclusion, the newly developed correlations will be useful in planning the lung delivery of next-generation inhaled medications, where achieving both low ET loss and targeted airway deposition, perhaps with excipient enhanced growth technology, are critical factors.

Simultaneous Estimation of Orlistat and Clomiphene by Hplc: Stability-Indicating Method Development and Validation.

Aim: To quantify Clomiphene and Orlistat in pharmaceutical formulations simultaneously, this study is set out to create a sensitive, fast, and accurate stability-indicating RP-HPLC method. Materials and Methods: The isocratic method was used to achieve the chromatographic separation of the Clomiphene and Orlistat mixture. A mobile phase was prepared using a 60:40% v/v ratio of acetonitrile to 0.01N Potassium dihydrogen orthophosphate (PH 4.8). The Agilent C18 column, with dimensions of 150 x 4.6mm, a 5µm particle size, and a flow rate of 1.0 mL/min was used. With an injection volume of 10.0 mL, the detection system was observed at a maximum wavelength of 240 nm. Results: The retention time for Orlistat was 2.12 minutes while that for Clomiphene was 2.88 minutes. Various factors, including heat, acidity, oxidation, photolysis, and alkalinity, were used to test the combined medication formulation of Clomiphene and Orlistat. To ensure that this method is accurate, precise, linear, and sensitive, it was validated according to the standards set out by the ICH. Conclusion: The run time was reduced to 6.0 minutes, enhancing the method’s precision and cost-effectiveness. Stability studies confirmed the technique’s suitability for assessing the degradation of Clomiphene and Orlistat. The proposed method is well-suited for routine analysis in pharmaceutical quality control.

Method Development and Validation for the Simultaneous Estimation of Lobeglitazone Sulphate and Glimepiride by HPLC Method.

A simple, precise, and accurate reverse-phase high-performance liquid chromatography (RP-HPLC) method was developed for the simultaneous estimation of lobeglitazone sulfate and glimepiride in bulk and tablet dosage forms. The method involved selecting various chromatographic parameters. Specifically, a new method was developed using a 250 mm × 4.6 mm (HSS) reverse-phase C18 column with 5 µm particle size (Shim-pack C18, 250 × 4.6 mm; 5 µm). The mobile phase consisted of 40 volumes of phosphate buffer (pH 3) and 60 volumes of acetonitrile, with methanol as the diluent, running as an isocratic elution. The flow rate was set at 1.0 mL/min, and UV detection was performed at 254 nm. The injection volume was 2 µL, and the total runtime was 10 minutes. The recoveries for lobeglitazone sulfate were found to be in the range of 101% to 100.6%, while those for glimepiride were in the range of 101.5% to 100%. The method’s accuracy is evident from these results. The inter-day and intra-day precision of the new method were both below the maximum allowable limit (RSD% ≤ 2.0), as per International Council on Harmonisation (Q2 R1) guidelines. The method exhibited a linear response, with correlation coefficient (r2) values of 0.9972% for pioglitazone and 0.998 for glimepiride. The validation parameters, such as accuracy, precision, linearity, specificity, stability in the analytical solution and robustness, met the acceptance criteria. Hence, this method can be effectively used for the simultaneous estimation of lobeglitazone sulfate and glimepiride in both bulk and pharmaceutical dosage forms.

Particle and bacterial colony emissions from garments and humans in pharmaceutical cleanrooms

Particles and bacteria released from operators in pharmaceutical cleanrooms significantly impact the quality of pharmaceutical products. Therefore, it is necessary to study particle and bacteria emissions from operators and their garments. This paper presents the results of experimental measurements of numbers of particles and bacterial emissions from integrated and split cleanroom garments, under different movement types and laundry conditions. The experiment demonstrated that the emission rate of 0.5 μm particles from split-type garments is approximately 2.0–3.5 times higher than that of integrated cleanroom garments, and 7.0–22.7 times for 5.0 μm particles. The particle emission rate of humans is closely related to the movement types, number of laundry cycles, and garment types. The maximum particle emission rates were obtained when wearing split cleanroom garment after 100 washes and performing knee bend, with 654603 P/min for 0.5 μm and 27185 P/min for 5.0 μm particles, respectively. The particle emission rate of humans is mainly caused by personnel movement, since the emission rate of garments accounts for at most 3.89 %. The bacteria colony of humans increases with the increase of laundry cycles of cleanroom garments. The maximum bacteria colony of integrated and split cleanroom garment were 4 CFU/plate and 9 CFU/plate with the laundry cycles of 100 times. The quantitative results of bacteria and particles emitted from pharmaceutical cleanroom operators are expected to ensure drug quality during production.

A green and sensitive electromembrane extraction (EME) method for the determination of dialkylphosphates in maternal urine and amniotic fluid

Organophosphates compounds are extensively used pesticides, whose metabolites, dialkyl phosphates, are considered as bioindicators of human exposure. Recently, research has indicated that they can affect thyroid endocrine function. Pregnant women are a particularly vulnerable cohort to these effects due to concerns about prenatal exposure to environmental pollutants. For the first time an electromembrane microextraction method is proposed for the simultaneous determination of seven dialkylphosphate metabolites in maternal urine and amniotic fluid, which is compatible with mass spectrometry detection and achieves highly sensitive levels of quantitation. Dialkylphosphates were extracted from a 10 mL donor solution at pH 7 into a 50 µL acceptor solution at pH 12 using 1-octanol as the supported liquid membrane and applying 60 V for 10 min at 600 rpm. The obtained extracts were analysed by ion pair liquid chromatography coupled to a triple quadrupole mass spectrometer, using an Acquity UPLC® BEH C18 column (100 mm × 2.1 mm i.d., 1.7 µm particle size) at 30 °C. Under optimal extraction conditions, the preconcentration factors were achieved were up to 178-fold, allowing for high sensitivity levels, in the order of ng mL−1. The limits of quantitation were within 0.075 ng mL−1 (diethyl thiophosphate) and 1.67 ng mL−1 (dimethyl phosphate) in maternal urine samples and within 0.015 ng mL−1 (diethyl thiophosphate) and 0.5 ng mL−1 (dimethyl dithiophosphate) in amniotic fluid samples. The comparative study revealed a significant improvement in terms of analysis time, sensitivity, greenness, and practicality. Finally, the applicability of the method for the determination of selected dialkylphosphates was demonstrated in paired maternal urine and amniotic fluid samples. These results suggest potential placental transfer to the offspring.

Particle motion under turbulent eddies: Inspiration for fine minerals flotation

Turbulent flow ubiquitous in flotation machines and contain multi-scale eddies. Compared to static environments, turbulence can increase particle kinetic energy and promote particle-bubble collision in mineral flotation. However, there have been few quantitative studies on turbulent eddies that affect particle motion, which limits the precise flow control of flotation processes. In this study, the motion characteristics of particles in isotropic turbulence were measured by particle tracking velocimetry, and the relationship between turbulent eddy and particle motion was quantitatively analyzed by 7-scale wavelet transform and fast Fourier transform. The measurement results show that the particle moves upward following a rotating turbulent eddy, and turbulent eddies with sizes of 35–119 µm and 127–288 µm drives the motion of dp = 74 µm and dp = 200 µm particles respectively. The turbulent acceleration of particles within a turbulent eddy can be calculated as aλ=Cε2/3λ-1/3. This study provides an eddy control basis for mineral flotation performance improvement.

Development and Validation of Novel RP-HPLC Method for the Simultaneous Estimation of Itraconazole and Secnidazole in Bulk and Pharmaceutical Formulations

Simple, accurate and precise RP-HPLC method for the simultaneous estimation of Itraconazole (ITZ) and Secnidazole (SEC) in bulk and pharmaceutical formulations has been developed and validated. The chromatographic analysis was performed on Shimadzu model equipped with SPD-20 AD UV detector, isocratic pump LC- 20 AD and loop injector. The chromatographic separation was performed using C18 column (250mm x 4.6mm i.d. and 5µm particle size). The analytes were monitored at 257nm using methanol: potassium dihydrogen phosphate buffer (PDP) pH 5.5 in the ratio of 90:10v/v with a flow rate of 1.5ml/min. The retention time was found to be 6.037 min for ITZ and 3.788 min for SEC. The linearity was found to be in the range of 10-50µg/ml for both ITZ and SEC with a regression coefficient of 0.999 and 0.998 for ITZ and SEC respectively. The method was validated in accordance with ICH guidelines for its linearity, precision, accuracy, robustness, ruggedness, LOD and LOQ. The recovery studies were carried out which confirmed the accuracy of the proposed method. LOD values for ITZ &amp; SEC was found to be 0.583µg/ml and 0.241µg/ml, respectively. LOQ values for ITZ and SEC was found to be 1.749µg/ml and 0.732µg/ml, respectively. The developed method was also found to be precise and robust for the simultaneous determination of ITZ and SEC in bulk and pharmaceutical formulations.

Study on the separation performance of a three-product hydrocyclone with overflow reseparation

This manuscript proposes a three-product hydrocyclone with overflow reseparation to reduce the particle misplacement in overflow, which achieves secondary separation by utilizing the after-energy of internal swirling flow. Numerical simulations and physical tests were applied to investigate the separation performance. The simulation results revealed that the coarser particles entrapped were effectively recovered by sideflow, the recovery of 20 μm particles in the overflow decreased by 16.71 % ∼ 23.09 % with significant fineness improvement compared with conventional hydrocyclone. The intensity of the internal centrifugal field decreased with the overflow separation chamber expanded, which resulted in an increased probability of particle misplacement during overflow. The test results revealed that the particle content of more than 20 μm in overflow was reduced by 2.44 % compared with conventional hydrocyclone, reducing the overflow separation chamber increased the sideflow ratio and solid phase yield, increased the difference in fineness between sideflow and overflow, and improved the narrow-grain separation performance.

Simultaneous Estimation of Pregabalin and Duloxetine Used to Treat Nerve Pain by Stability Indicating RP-HPLC Method Using the QBD Approach

Objective: A novel stability indicating RP-HPLC method was developed and validated for the simultaneous estimation of Pregabalin and Duloxetine by using the QBD approach. Method: To determine the optimal parameters for the duloxetine and pregabalin study, we used Design Expert version 13.0 in this work. The mobile phase consisted of 0.8 ml/min of methanol: water (80:20, v/v) with o-phosphoric acid-adjusted pH 3.A 250 mm × 4.6 mm ID, 5 μm particle size Cosmosil C18 column was used. The UV-3000-M detector was used to detect at 218 nm. Results: Duloxetine's retention time was 7.153 ±0.1 min, whereas Pregabalin's was 4.481±0.1 min. The ICH parameters like linearity, accuracy, robustness, ruggedness, LOD and LOQ, and system suitability were determined. Likewise, the tailing factors were found to be 1.27 and 1.26, while the theoretical plates of duloxetine and pregabalin were found to be 8313 and 8549, respectively. The recovery study shows the results (99.37–99.84% for pregabalin and 99.03–99.74% for duloxetine), and the precision was obtained with a %RSD of less than 2%. The result of the assay was 99.92 % for pregabalin and 99.39% for duloxetine. The developed method was used for the forced degradation study. The Box-Behnken design experiment using Design Expert 13.0 was adopted for the QBD approach. Conclusion: All the values obtained for different parameters were within the acceptable range of ICH. The developed method can be routinely used for the simultaneous estimation of Pregabalin and Duloxetine by using the QBD approach.

Tribological Properties of Nitrate Graphite Foils.

This study investigates the tribological properties of graphite foils (GF) with densities of 1.0, 1.3, and 1.6 g/cm3, produced from purified natural graphite of different particle sizes (40-80 μm, 160-200 μm, >500 μm). Surface roughness was measured after cold rolling and friction testing at static (0.001 mm/s) and dynamic conditions (0.1 Hz and 1 Hz). Results showed that static friction tests yielded similar roughness values (Sa ≈ 0.5-0.7 μm, Sq ≈ 0.5-1.0 μm) across all densities and particle sizes. Dynamic friction tests revealed increased roughness (Sa from 0.7 to 3.5 μm, Sq from 1.0 to 6.0-7.0 μm). Friction coefficients (µ) decreased with higher sliding speeds, ranging from 0.22 to 0.13. GF with 40-80 μm particles had the lowest friction coefficient (µ = 0.13-0.15), while 160-200 μm particles had the highest (µ = 0.15-0.22). Density changes had minimal impact on friction for the 40-80 μm fraction but reduced friction for the 160-200 μm fraction. Young's modulus increased with density and decreased with particle size, showing values from 127-274 MPa for 40-80 μm, 104-212 MPa for 160-200 μm, and 82-184 MPa for >500 μm. The stress-strain state in the graphite foil samples was simulated under normal and tangential loads. This makes it possible to investigate the effect of the anisotropy of the material on the stress concentration inside the sample, as well as to estimate the elasticity modulus under normal compression. Structural analyses indicated greater plastic deformation in GF with 40-80 μm particles, reducing coherent-scattering region size from 28 nm to 24 nm. GF samples from 160-200 μm and >500 μm fractions showed similar changes, expanding with density increase from 18 nm to 22 nm. Misorientation angles of GF nanocrystallites decreased from 30° to 27° along the rolling direction (RD). The coherent scattering regions of GF with 40-80 μm particles increased, but no significant changes in the coherent scattering regions were observed for the 160-200 μm and >500 μm fractions during dynamic friction tests. Microstrains and residual macrostresses in GF increased with density for all fractions, expanding under higher friction-induced loads. Higher values of both stresses indicate a higher level of accumulated deformation, which appears to be an additional factor affecting the samples during friction testing. This is reflected in the correlation of the results with the roughness and friction coefficient data of the tested samples.

Mathematical Formulations for Predicting Pressure Drop in Solid–Liquid Slurry Flow through a Straight Pipe Using Computational Modeling

The study establishes two mathematical formulations to predict the pressure drop in a solid–liquid slurry flowing through a straight pipe. Employing the Eulerian–Eulerian RNG k-ε model, the computational investigation uses water as the carrier fluid and glass beads as solid particles. The analysis spans various particle sizes (d50 = 75–175 μm), volumetric concentrations (Cvf = 10–50%), and velocities (Vm = 1–5 m/s). The first model, developed using the MATLAB curve-fitting tool, is complemented by a second empirical equation derived through non-polynomial mathematical formulation. Results from both models are validated against existing experimental and computational data, demonstrating accurate predictions for d50 = 75–175 µm particles within a Reynolds number range of 20,000 ≤ Re ≤ 320,000.