Flow Rate Gradient Research Articles

Development and validation of RP-HPLC method for quantification of trace levels of topical corticosteroids in ambiphilic cream

AbstractCorticosteroids are anti-inflammatory and immunosuppressant drugs. Topical corticosteroids formulations (ointments, creams, gels) are used in the treatment of different types of dermatitis and urticaria. Considering their therapeutic and whitening effects, they are frequently used for counterfeiting of cosmetic products. Corticosteroids can cause different local and systemic side effects. HPLC method is often chosen for their analysis, because it is selective, sensitive, precise, simple and fast.The aim of this study was optimization and validation of RP-HPLC method with UV detection for determination of trace levels of corticosteroids in ambiphilic creams. This method is used for qualitative and quantitative analysis of evaluated corticosteroids.Mometasone furoate, hydrocortisone acetate, fluocinonide, fluocinolone acetonide, betamethasone, betamethasone dipropionate and triamcinolone acetonide were evaluated. Separation was performed on Inertsil® ODS-3V 250 × 4.6 mm, 5 μm chromatographic column. Mobile phase was mixture of acetonitrile and water 50:50 (v/v) with gradient elution and flow rate 1 mL min−1. Column temperature was held on 40 °C and UV detection was performed at 240 nm.Selectivity, linearity, accuracy, precision and limit of quantification (LOQ) were evaluated. Method is selective because ambiphilic cream base peaks and corticosteroids peaks were not overlapping. Linearity was confirmed since correlation coefficient was 1 for all compounds. Accuracy and precision were evaluated for hydrocortisone acetate and betamethasone dipropionate. Determined Recovery values were in range of 70–130%. Both RSD values (21.46% and 9.59%) were lower than 30%. Method is highly sensitive since LOQ concentrations were in ng mL−1 range.All evaluated parameters of validation were in accordance with regulatory requirements. Validated RP-HPLC method can be used for qualitative and quantitative analysis of selected corticosteroids in ambiphilic creams.

Nonlinear Flow Properties of Newtonian Fluids through Rough Crossed Fractures

The nonlinear flow properties of Newtonian fluids through crossed fractures are estimated by considering the influences of length, aperture, and surface roughness of fractures. A total of 252 computational runs are performed by creating 36 computational domains, in which the Navier-Stokes equations are solved. The results show that the nonlinear relationship between flow rate and hydraulic gradient follows Forchheimer’s law–based equation. When the hydraulic gradient is small (i.e., 10−6), the streamlines are parallel to the fracture walls, indicating a linear streamline distribution. When the hydraulic gradient is large (i.e., 100), the streamlines are disturbed by a certain number of eddies, indicating a nonlinear streamline distribution. The patterns of eddy distributions depend on the length, aperture, and surface roughness of fractures. With the increment of hydraulic gradient from 10−6 to 100, the ratio of flow rate to hydraulic gradient holds constants and then decreases slightly and finally decreases robustly. The fluid flow experiences a linear flow regime, a weakly nonlinear regime, and a strongly nonlinear regime, respectively. The critical hydraulic gradient ranges from 3.27 × 10−5 to 5.82 × 10−2 when fracture length = 20–100 mm and mechanical aperture = 1–5 mm. The joint roughness coefficient plays a negligible role in the variations in critical hydraulic gradient compared with fracture length and/or mechanical aperture. The critical hydraulic gradient decreases with increasing mechanical aperture, following power-law relationships. The parameters in the functions are associated with fracture length.

Investigation of Nano-Silica Solution Flow through Cement Cracks

Cement cracks are one of the most common failures in oil and gas wells. Cracks can reduce cement strength, resulting in a loss of zonal isolation and fluid leak. Placement of gels of nanoparticles (NPs) in the cracks is considered as a promising solution to solve the problem. It is highly desirable to know if the flow behavior of the NPs solutions is predictable when they are squeezed into the cracks. Experimental tests were performed in this study to investigate the flow behavior of nano-silica solutions in ducts of cross-sections of rectangular shape. The linear relationship between flow rate and pressure gradient and the calculated Reynolds number values suggests laminar flow in the ducts. However, the Hagen–Poiseuille correlation for laminar flow does not describe the flow behavior of the nano-silica solution. The classic hydraulic model with hydraulic diameter describes the nano-silica flow behavior with an average error of 12.38%. The cause of discrepancies between the flow models and the measured data is not known. It can be attributed to the NPs–NPs frictions and NPs–wall frictions in the rough ducts that were not considered in the flow models.

Implementation of two sustainable chromatographic methods for the simultaneous micro-quantitation and impurity profiling of metformin and rosuvastatin in recently approved fixed dose pills: Greenness and whiteness studies

Rosuvastatin-Metformin is an emerging fixed dose combination (FDC) for the treatment of diabetes mellitus-associated dyslipidemia. Generally, the beneficial outcomes of FDC in reduction of pills burden, cost and complexity of medications protocols, encouraged analysts and we in turn for the development of rapid sustainable analytical methods for the simultaneous estimation of such important drug combinations. Within this framework, two validated analytical methodologies have been implemented for the neat separation and quantitation of metformin (MET) and rosuvastatin (RSV) in presence of the pharmacopeial impurities cyanoguanidine (CYG) (impurity A of MET) and the rosuvastatin-related substance B (RSV-impurity B). The latter was freshly prepared and then confirmed using Liquid Chromatography-Mass spectrometry (LC-MS). Method I represented the first electro-driven separation method for the assay of this FDC using Micellar Electrokinetic Chromatography (MEKC). The optimized conditions were 50 mM borate buffer containing 100 mM sodium dodecyl sulfate (SDS) at pH 9.2 using a deactivated fused silica capillary (50 cm effective length × 50 μm id). Method II was High Performance Liquid Chromatography (HPLC) method using Microsorb MV-C18 (4.6 × 250 mm, 5 μm particle size) column with 20 mM sodium dihydrogen phosphate buffer (pH 3.5), acetonitrile and methanol as mobile phase constituents. The separation was achieved with a linear gradient program and flow rate 1.5 mL/min all over the run. The Diode Array Detector (DAD) detector was set at wavelengths 243 nm for RSV and 235 nm for MET in both methods. The 4 peaks were separated in about 8 and 5 min for methods I and II, respectively. Linear relationships were obtained between peak areas and concentrations of metformin and rosuvastatin in the ranges 10–100 μg/mL for MEKC and 1–150 μg/mL for HPLC. The 2 techniques fulfilled the International Council for Harmonization (ICH) validation criteria, as well as the green and white analytical chemistry principles which were evaluated using the trendiest AGREE, hexagon and RGB12 tools. The interpretation of scores indicated that the suggested methods outperformed the reported methods in terms of eco-friendliness and sustainability. They offered fast, feasible, stability indicating and accurate analysis of both drugs in bulk and in pills.

AQbD based green UPLC method to determine mycophenolate mofetil impurities and Identification of degradation products by QToF LCMS

We report an ideal method for quantifying impurities in mycophenolate mofetil drug substances and their oral suspension preparations. We developed a systematic and eco-friendly analytical approach utilizing quality by design (QbD) and green chemistry principles. Initially, the critical method parameters (CMPs) were screened using a D-optimal design. The robust final method conditions were optimized using a systematic central composite design (CCD). Through graphical and numerical optimization, the protocol conditions were augmented. The pH of mobile phase buffer (25 mM KH2PO4) (MP-A), initial gradient composition (% MP-A), flow rate (mL min−1), and column oven temperatures (°C) are 4.05, 87, 0.4, and 30, respectively. The best possible separation between the critical pairs was achieved while using the Waters Acquity UPLC BEH C18 (100 × 2.1) mm, 1.7 µm analytical column. A mixture of water and acetonitrile in the ratio of 30:70 (v/v) was used as mobile phase-B for the gradient elution. The analytical method was validated in agreement with ICH and USP guidelines. The specificity results revealed that no peaks interfered with the impurities and MPM. The mean recovery of the impurities ranged between 96.2 and 102.7%, and the linearity results r > 0.999 across the range of LOQ – 150%. The precision results (%RSD) ranged between 0.8 and 4.5%. The degradation products formed during the base-induced degradation were identified as isomers of mycophenolic acid and sorbitol esters using Q-ToF LC–MS and their molecular and fragment ion peaks. The developed method eco-friendliness and greenness were assessed using analytical greenness (AGREE), green analytical procedure index (GAPI), and analytical eco score, and found it is green.

Speeding up temperature-responsive × reversed-phase comprehensive liquid chromatography through the combined exploitation of temperature and flow rate gradients

Comprehensive two-dimensional liquid chromatography (LC×LC) can provide enhanced resolving power and higher peak capacities for the separation of complex samples. The transfer of fractions of too high eluotropic strength from the first dimension, however, can lead to peak broadening. This process is related to the column dimensions, the flow rates, mobile phase compositions, and stationary phase compatibility. Temperature-responsive LC (TRLC) uses a smart polymer coupled to silica (poly(N-isopropylacrylamide), pNIPAAm), that exhibits a change in polarity upon modest variations in column temperature. Retention is thus modulated by temperature and not by organic solvents, allowing for the use of purely aqueous mobile phases. As these aqueous mobile phases depict a very low eluotropic strength on a reversed-phase column, it facilitates band refocusing at the second-dimension column head in TRLC×RPLC. One of the remaining obstacles of TRLC is the long analysis time. In this research, the potential of this column combination in terms of analyte refocusing will be exploited. First, it is shown that upwards flow gradients can be implemented in the first dimension of TRLC×RPLC. As the flow in the second dimension is maintained at a constant level, a first-dimension flow gradient does not lead to impaired sensitivity and has no negative effects on the resulting peak size. Then, the novel combination of a downwards temperature gradient with an upwards flow gradient will be introduced to speed up the analyses further. Analysis time was, depending on the method used, reduced by 36–54%, as demonstrated by the analysis of mixtures of food additives, phenolic compounds, and small molecule pharmaceuticals mimicking impurity analysis at a 0.05% level.

Development of the composition and research of soft dosage forms with carbon dioxide extract from Scabiosa ochroleuca L.

The article presents the research results on the development of dosage forms with carbon dioxide extract from pale yellow scabious (Scabiosa ochroleuca L.) for topical use. The lipophilic and hydrophilic ointments bases under the conditional name "Scabiol" were taken as objects of research. Rheological studies were carried out using a rotary viscometer of the "Reotest-2" type (Germany) using a cell consisting of systems of coaxial cylinders (S/S1). The speed of rotation of the inner cylinder was regulated by changing the gap between the cylinders, as well as the speed of rotation, and the tangential shear stress was determined. The study of the structural and mechanical properties of the "Scabiol" ointments was carried out at temperatures of 25, 40 and 55 oC. The shear stress and dynamic viscosity of the ointments were measured. Based on the obtained results, graphs were constructed that characterize the changes in the logarithm of the effective viscosity from the gradient of the shear flow rate, and the dependence of the gradient of the shear flow rate on the shear stress. The results of rheological studies showed the absence of structural changes in the shear field with the destruction or appearance of new compounds; the thixotropic properties of lipophilic and hydrophilic «Scabiol» ointments bases were also established. As a result of the study of the antimicrobial and antifungal activity of dosage forms with carbon dioxide extract of pale yellow scabious, it was found that to some extent, ointments inhibit the growth of test cultures in vitro. High-intensity antimicrobial activity was shown by lipophilic ointment "Scabiol" against Staphylococcus aureus, and Escherichia coli.

The Effect of Trace Ions on the Performance of Reverse Electrodialysis Using Brine/Seawater as Working Pairs

Harvesting the salinity gradient power (SGP) between concentrated brine discharged from seawater desalination installations and seawater and converting into electric energy by reverse electrodialysis (RED) is a promising technique. However, trace ions in brine and seawater may affect the performance of the RED stack, and little attention has been focused on this issue. Therefore, the influences of trace ions in seawater and concentrated brine are analyzed in this work. The effects of these ions on power density, open-circuit voltage, and internal resistance of the RED stack are analyzed by configuring manual seawater and concentrated brine including K1+, Mg2+, SO42-, and Ca2+. Experimental results show that divalent ions (Mg2+, SO42-, and Ca2+) can significantly increase the internal resistance of the RED stack and reduce power density. Mg2+ especially has the largest reduction in the output power of the stack. Oppositely, potassium ions (K1+) in feed solutions will reduce the internal resistance and improve power output. In addition, increasing the salinity gradient of feed solutions, temperature, and flow rate can increase open-circuit voltage and power density, and reduce inner power consumption of the RED stack. This study can provide references for the recovery of SGP in seawater desalination plants.

Measurements and estimation of flow velocity in mobile bed rills

Rills are primary sediment sources and hillslope water/sediment runoff transport channels. Water flow velocities in rills are easily affected by bed condition over eroding and non-eroding slopes, which is an important hydrodynamic process in soil erosion research. This research is done to demonstrate the poorly understood “feedback mechanism” related to slope independence of flow velocity to slope gradient. A series of experiments were done on silt loam soil slopes to measure water flow velocity in rills under nine unit width flow rates (q) (0.17 × 10−3, 0.33 × 10−3, 0.67 × 10−3, 1.33 × 10−3, 2.67 × 10−3, 5.33 × 10−3, 10.67 × 10−3, 21.33 × 10−3, and 42.67 × 10−3 m3/(s·m)) combined with four slope gradients (8.7%, 17.6%, 26.8%, and 36.4%), in which mobile bed rills were monitored. For unit flow velocity under q ≤ 1.33 × 10−3 m2/s, independence of flow velocity to slope was obtained. However, the results indicated that slope gradient combined with a higher unit flow rate contributed to better velocity prediction and fitted with a segmented equation well (R2 = 0.95). A feedback mechanism was able to verify that the increase in roughness directly dissipated flow energy to reduce flow velocity, but cannot completely counterbalances steep slope effect. The experimental results showed that erosion-caused morphological changes on soil slopes reduce flow velocity by half due to an increase in bed roughness. Therefore, the current experimental measurements considering a wide range of flow rate and slope gradient conditions is useful to reveal the steep slope effect in mobile bed rills. The analysis showed that, for the investigated conditions, the flow velocity is a slope gradient- and flow rate-dependent parameter.

Heat transfer performance analysis of seawater heat exchange pipelines in deep seawater closed cooling air conditioning system

The efficiency improvement of traditional seawater source heat pump system is limited and pipelines of the open seawater cooling air conditioning system experience scaling and corrosion. To overcome these problems, this paper proposes a deep seawater closed cooling air conditioning system. The system directly uses the closed heat exchange pipeline to exchange heat with the deep seawater and extracts the seawater cooling capacity for cooling. Numerical simulation is used to study the effects of different pipe diameters, flow rates, and inlet water temperatures on the heat transfer performance of vertical inlet sections, submarine heat exchange coils and vertical outlet sections. Since seawater has temperature and flow rate gradients in the vertical direction, the use of a hydraulic calculation table of the vertical pipe section and the calculation diagram of design and selection line of submarine heat exchange coil is proposed. Insulating subsections of the outlet section by dividing the section into 3 °C based on the seawater temperature is proposed. And the subsection insulation layer thickness corresponding to different pipe diameters are given. This study proposes a calculation method for the selection of key design parameters of deep seawater closed cooling air conditioning systems, providing a new method for making full use of seawater resources.

A Theoretical Study of Reverse Roll Coating for a Non-Isothermal Third-Grade Fluid under Lubrication Approximation Theory

The flow of non-Newtonian fluids is extremely important in a variety of industrial applications and processes, including painting, printing, and coating. The goal of this paper is to develop a mathematical model for an incompressible, non-isothermal third-grade fluid as it travels through a minor gap between two heated rolls that are revolving in the opposite direction. Using appropriate dimensionless parameters, the dimensionless version of the governing equations is constructed. To simplify the nondimensional form of the governing equations, the LAT (lubrication approximation theory) is applied. It is mentioned that the perturbation approach should be used. It is a very important tool in modern mathematical physics and practical fluid mechanics, and it is used a lot. Through perturbation techniques, exact solutions for velocity distribution, flow rate, temperature distribution, and pressure gradient are offered. To observe the flow pattern, streamlines are also drawn. Numerical outcomes of some substantial engineering quantities like flow rate, roll separation force, power input, and pressure distribution are found. Some outcomes are displayed graphically although others are presented in tabular form. We have observed that the third-grade parameters give a way to control velocity, pressure gradients, flow rate, and coating thickness. Further, increasing the velocities ratio values lowers the coating thickness on the web. Furthermore, the Brickman number has a significant influence on the temperature profile and has increased with the increase in the Brickman number. Both the model and the numerical calculations are in agreement with the viscous fluid model that is already present in the literature.

Development of a Simultaneous Sulfadiazine, Sulfamethoxazole, and Tetracycline Antibiotic Level Determination Method with High-Performance Liquid Chromatography

Sulfonamides and tetracyclines are a group of synthetic antibacterials that are widely used in veterinary practice for the treatment and prevention of infections in animals that can be consumed by humans. The purpose of this study was to determine the optimum conditions for High-Performance Liquid Chromatography for simultaneous analysis of sulfadiazine, sulfamethoxazole, and tetracycline and meet the validation requirements. The research method used is the HPLC method. The instruments used are Agilent 1220 Infinity II low-pressure dual-channel gradient valve, variable wavelength detector (VWD) BI detector, the column used is Agilent 5 TC-C18 (250 x 4.6 mm), motion phase A = acetic acid 0.08%: acetonitrile (9:1) and motion phase B = methanol with a flow rate gradient of 0.5 mL/minute and UV-VIS detector at wavelength 295 hm. The results showed that the method of determining the levels of sulfadiazine, sulfamethoxazole, and tetracycline met the requirements of selectivity, accuracy, precision, linearity, LOD, and LOQ and could be applied to fish samples. The accuracy parameter test obtained recovery results between 96.99%-103.16% at all sample concentration levels of 80%, 100%, and 120%. Testing the precision parameters showed that all sample concentrations were 100% repeated for 6 times replications, fulfilling the precision requirements, namely, the concentration of ≥10 ppm was < 7.3%. The linearity test showed that the correlation coefficient of sulfadiazine was 0.999, sulfamethoxazole was 0.999, and tetracycline was 0.998. LOD and LOQ values of sulfadiazine 1.15 ppm and 3.84 ppm, sulfamethoxazole LOD 2.51 ppm and LOQ 8.37 ppm, and tetracycline LOD 3.37 ppm and LOQ 11.22 ppm. Applications to fish samples were carried out by addition and obtained levels of 14.79 ppm sulfadiazine, 14.01 ppm sulfamethoxazole, and 45.05 ppm tetracycline.

Dynamics of heat absorbing and radiative hydromagnetic nanofluids through a stretching surface with chemical reaction and viscous dissipation

The hydromagnetic dissipative, heat-absorbing, chemically reactive and optically thick radiative flow of nanofluid over a stretchable surface together with heat and mass transport phenomena is investigated. The prevailing partial differential equations (PDE) of the mathematical model are changed by incorporating apt similarity variables in the form of nonlinear similarity equations. Further, these similarity equations are solved numerically utilizing the Runge-Kutta Fehlberg technique in conjunction with the shooting method. For the numerical explorations, three kinds of nanofluids are prepared by disseminating very fine nanoparticles of titanium oxide (TiO2), aluminium oxide (Al2O3) and copper (Cu) into water. The significance of numerous regulatory flow parameters on the nanofluid velocity, nanofluid temperature, local Nusselt number, species concentration, wall velocity gradient and mass flow rates are examined through different graphical results. Additionally, a quadratic regression approximation analysis is accomplished to analyze the connection between the heat transport rate and regulatory flow parameters. The numerical results reveal that the temperature of Cu-water based nanofluid temperature gets enhanced owing to improvement in the strength of radiation, viscous dissipation and magnetic effects. Further, regression approximation analysis unveils that a slight change in the velocity slip parameter leads in the optimal perturbation in both the shear stress values and heat transfer rate at the stretchable surface. Finally, the validation of numerical results and the developed algorithm of employed computational technique have been done by making a comparison of computed results with the available results under restricted situations.

An in-vivo herb-drug interaction study of Tinospora cordifolia extract on the pharmacokinetics of gliclazide in normal Wistar rats

Background and Aims: Tinospora cordifolia (Willd.) Miers (TC), from the Menispermaceae family, is a well-known traditional herb used to treat diabetes mellitus and a variety of other ailments, according to traditional Indian literature. Herbal treatments are commonly used as alternatives to medicines. Anti-diabetic herbal medicines containing TC are available in the market. TC has been identified as a powerful CYP2C9 inhibitor, boosting the risk of herb-drug interactions (HDI) when used with medications metabolized via the CYP pathway. The present study evaluated the pharmacokinetic HDI of TC extract with Gliclazide (GL) after oral co-administration in Wistar rats using in vivo pharmacokinetic studies. Methods: A simple, sensitive & accurate RP-HPLC/PDA method was developed and validated. Chromatographic separations were performed on a C18 analytical column with a mobile phase of acetonitrile and 40 mM ammonium acetate buffer (55:45 v/v) pH 3.0 and flow rate gradient programming. The drug concentrations in plasma were measured using the RP-HPLC method after oral co-administration of TC extract (100 mg/kg) with GL (8.3 mg/kg) in Wistar rats. Results: The pharmacokinetic (PK) interaction studies showed that the bioavailability of GL had significantly increased, with a significant influence on Cmax, AUC0-48, and suppression of volume of distribution (Vd), with no change in Tmax. Conclusion: The results obtained from this in vivo study proposed that there is a potentially significant PK HDI when GL and TC extract are administered together. This knowledge of potential HDI could be beneficial to healthcare providers and diabetic patients on GL medication. Further research is needed to anticipate this pharmacokinetics HDI of GL in humans.

Comparison of the separation of proteins of wide-ranging molecular weight via trilobal polypropylene capillary-channeled polymer fiber, commercial superficiously porous, and commercial size exclusion columns.

Reversed phase and size-exclusion chromatography methods are commonly used for protein separations, although they are based on distinctly different principles. Reversed phase methods yield hydrophobicity-based (loosely-termed) separation of proteins on porous supports, but tend to be limited to proteins with modest molecular weights based on mass transfer limitations. Alternatively, size-exclusion provides complementary benefits in the separation of higher mass proteins based on entropic, not enthalpic, processes, but tend to yield limited peak capacities. In this study, microbore columns packed with a novel trilobal polypropylene capillary-channeled polymer fiber were used in a reversed phase modality for the separation of polypeptides and proteins of molecular weights ranging from 1.4 to 660kDa. Chromatographic parameters including gradient times, flow rates, and trifluoroacetic acid concentrations in the mobile phase were optimized to maximize resolution and throughput. Following optimization, the performance of the trilobal fiber column was compared to two commercial-sourced columns, a superficially porous C4-derivatized silica and size exclusion, both of which are sold specifically for protein separations and operated according to the manufacturer-specified conditions. In comparison to the commercial columns, the fiber-based column yielded better separation performance across the entirety of the suite, at much lower cost and shorter separation times.

A FRACTAL MODEL OF LOW-VELOCITY NON-DARCY FLOW CONSIDERING VISCOSITY DISTRIBUTION AND BOUNDARY LAYER EFFECT

Seepage flow in low permeability reservoirs is strongly influenced by the boundary layer, which is characterized by a low-velocity non-Darcy flow phenomenon, and a nonlinear relationship between velocity and pressure gradient. The viscosity is not uniformly distributed in the pore throat and has a great effect on the nonlinear flow behavior. In this paper, a low-velocity non-Darcy flow model is proposed. By quantitatively characterizing the boundary layer thickness and considering the non-uniform distribution of viscosity for the first time, a modified Hagen–Poiseuille equation combining the boundary layer effect and viscosity distribution in a single capillary is derived. Then, the analytical expression of the nonlinear relationship between the flow rate and pressure gradient in the fractal porous media is established, assuming that the pores in the tight formation are fractal distribution. Finally, the validity of the model is verified by experimental data. The relative error between the model and experimental data, with a permeability smaller than 3mD, is 3.27%. And the parameters affecting low-velocity non-Darcy flow are also analyzed. The results showed that the influence of boundary layer is one of the causes of low-velocity non-Darcy flow in tight reservoir. The study has also revealed that the non-uniform distribution of viscosity in the pore throat has a great influence on the nonlinear flow, which is often neglected in previous works.

Productivity for free: Residence time gradients during loading increase dynamic binding capacity and productivity

• An algorithm to improve productivity and dynamic binding capacity in protein chromatography. • A controller to optimize the flow rate gradient during loading. • The theoretical concept has been validated by chromatography experiments. • The algorithm allows a productivity increase of 68% in Protein A chromatography without additional expense. Traditional chromatographic purification steps consist of long loading steps at a constant residence time, especially during early stages of the downstream process. The breakthrough behavior of the product is usually well defined. This information can be used to optimize the loading phase by starting the loading phase at a low residence time and gradually increasing the residence time to boost productivity and resin utilization. Process modeling of the loading of lysozyme on a Toyopearl SP-650C stationary phase, a strong cation exchanger, revealed optimal residence time gradients. These gradients result in a faster breakthrough in the time domain, while having the same breakthrough as constant residence time loading, in the volume domain. Modeling also revealed that a delayed start of the gradient further increases productivity. Eventually, several mathematical optimizations were employed to ensure the optimality of the idea. We confirmed the process model results in lab experiments using lysozyme breakthrough in ion-exchange chromatography and monoclonal antibody breakthrough in protein A affinity chromatography. Productivity of the loading step could be increased by 68 % from 40.8 to 68.7 g L -1 h −1 resin for protein A chromatography while retaining the same breakthrough behavior and better manufacturability of unstable proteins. Consequently, the bound fraction of protein is maintained above 99 %. This affords similar productivity gains as multicolumn chromatography while employing an easy-to-implement process model that can be used on conventional systems.

The Influence of Elasticity on Peristaltic Flow of Nanofluid in a Tube

In this paper, a mathematical model is proposed to study the influence of elasticity on peristaltic flow of nanofluid in a vertical tube with temperature dependent viscosity. The expressions for axial velocity, temperature, flux and pressure gradient are derived. The different nanofluids suspensions are consider to analyze the influence of elasticity on flux variation. Application of blood flow through veins is studied by expressing relationship between pressure gradient and volume flow rate in an elastic tube. The effect of different pertinent parameters on the flow characteristics of nano fluid in an elastic tube with peristalsis is analyzed through graphs. The variation in flux for different nanofluids like pure water H2O, Copper-water nanofluid CuO + H2O, Silver-water Ag + H2O and Titanium oxide-water nanofluid TiO2 + H2O are illustrated through graphs. The variation in flux for various physical parameters such as amplitude ratio, heat source parameter, Grashof number, viscosity parameter and elastic parameters are discussed. The flux takes higher values for nano particles case when compared to pure water. The flux enhances with amplitude ratio, Grashof number, heat source/sink factor and viscosity factor. The flux is more for the Titanium oxide-water nanofluid TiO2 + H2O when compared to remaining cases. The important observation is that pressure rise along mean flow rate is increase due to raise in temperature of source or sink in puming region and decreases in co pumping region. In the absence of elastic parameter (α″ = 0), the results observed in the present study are similar to that of results observed by O. A. Beg et al., Results in Physics 7, 413 (2017).

Framework to characterize nonlinear flow through pervious concrete

Pervious concretes have been increasingly used since they allow for better water flow. Flow through pervious concrete is usually assessed with Darcy's law, which presupposes linearity between flow rate and hydraulic gradient. However, some researchers reported this does not always hold, especially at faster flows. In such cases, Forchheimer's law may be used. In this paper, criteria for delimiting flow regimes was applied to evaluate hydraulic behavior. Forty-two specimens had their porosities measured and were tested in a constant head permeameter. Although low to moderate hydraulic gradients were applied, resulting flows already showed to be non-Darcian. A dimensionless permeability parameter engendered by the mentioned approach was able to adequately and unequivocally grade the flow resistance offered by each specimen. Correlations between this parameter and porosity were obtained and bestowed rich interpretations of how heterogeneity in pervious concretes impacts flow behavior. This may be key for designing better pervious concretes.

Analysis of short-chain bioactive peptides by unified chromatography-electrospray ionization mass spectrometry. Part I. Method development

A method to analyse short-chain bioactive peptides (MW < 800 Da) and their impurities was developed with a unified chromatography (UC) analysis, including a wide mobile phase gradient ranging from supercritical fluid to near-liquid conditions, with UV and electrospray ionization mass spectrometry detection (ESI-MS). Four stationary phases and three mobile phase compositions were examined. Ten model peptides were first selected to identify the best operating conditions, including five linear tripeptides and five cyclic pentapeptides, with log P values ranging from -5.9 to 3.6, and including isomeric species. Derringer desirability functions were designed to identify optimal operating conditions based on 7 criteria, namely the number of peaks detected (including all impurities resolved), the proportion of the chromatogram occupied by target peaks, the least favourable resolution observed between the main peptide and impurities, peak shape features (asymmetry and peak width at half height), and finally the signal-to-noise ratio observed both with UV (210 nm) and ESI-MS in positive ionization mode.The optimum conditions were obtained on Ascentis Express OH5 stationary phase, with a mobile phase composed of carbon dioxide and methanol, comprising 2% water and 20 mM ammonium hydroxide. The final gradient program ranged from 5 to 80% co-solvent in CO2, with a reversed flow rate gradient ranging from 3.0 to 1.5 mL/min. Back-pressure was set at 120 bar and the column oven temperature at 60°C. Optimal conditions were applied to a large set of 76 peptides (34 linear tripeptides and 42 cyclic pentapeptides) and provided adequate scattering of the peaks in the retention space, together with some separation of isomeric species, particularly for the cyclic peptides.