Quality risk assessment and DoE – Practiced validated stability-indicating chromatographic method for quantification of Rivaroxaban in bulk and tablet dosage form

A systematic DoE and Analytical Quality by Design (AQbD) approach was utilized for the development and validation of a novel stability indicating high-performance thin–layer chromatographic (HPTLC) method for Rivaroxaban (RBN) estimation in bulk and marketed formulation. A D-optimal design was used to screen the effect of solvents, volume of solvents, time from spotting to development and time for development to scanning. ANOVA results and Pareto chart revealed that toluene, methanol, water and saturation time had an impact on retention time. The critical method and material attributes were further screened by Box-Behnken design (BBD) to achieve optimal chromatographic condition. A stress degradation study was carried out and structure of major alkaline degradant was elaborated. According to the design space, a control strategy was used with toluene: methanol: water (6:2:2) and the saturation time was 15 min. A retention factor (RF) of 0.59 ± 0.05 was achieved for RBN using chromatographic plate precoated with silica gel at detection wavelength 282 nm with optimized conditions. The linear calibration curve was achieved in the concentration range of 200–1,200 ng/band with r 2 > 0.998 suggesting good coordination between analyte concentration and peak areas. The quadratic model was demonstrated as the best fit model and no interaction was noted between CMAs. The optimized HPTLC method was validated critically as stated in International Conference on Harmonization (ICH) Q2 (R1) guideline and implemented successfully for stress degradation study of RBN. The developed HPTLC method obtained through AQbD application was potentially able to resolve all degradants of RBN achieved through forced degradation study. The obtained results demonstrate that a scientific AQbD approach implementation in HPTLC method development and stress degradation study drastically minimizes the number of trials in experiments, ultimately time and cost of analysis could be minimized.

Predicting the Thickness of the Hardening Coating during Diffusion Metallization of Cast Iron

The article presents the calculations of diffusion indices of saturation of high-strength cast iron VCh 60 from powder filling. Carbide-forming elements were used as diffusers: vanadium, chromium and manganese. As a result of the research, empirical equations have been established for predicting the thickness of strengthening diffusion coatings depending on the temperature and saturation time.

Removal of chromium and Iron using mixed adsorbent for synthetic and industrial samples in a continuous column reactor

he results of the experiments showed that bed weight, flow rate, and initial metal ion concentration all play a role in the removal of Cr (III) and Fe (II). The optimized break through curve was obtained at 36cm bed height and 10ml/min for chromium where 97.5 to 100% removal was observed at a saturation time of 500-600 min. With the increase in bed height from 12cm to 36cm, both the breakthrough and saturation times for Cr (III) increased. The break through time at 12cm, 24cm, 36cm and 10ml/min for Cr (III) were 70 min, 105 min, and 35 min respectively. The saturation time for Cr (III) at 12cm, 24cm, 36cm and 10ml/min were 460 min, 490 min, and 500 min respectively. Similarly, the break through time for Fe (II) at 12cm, 24cm, 36cm and 10ml/min were 70 min, 80 min, and 100 min respectively. At 12cm, 24cm, 36cm, and 10ml/min, the saturation time for Fe (III) was 340 minutes, 360 minutes, and 430 minutes, respectively. Overall in the column performance comparison between synthetic solution and industrial effluents for chromium, synthetic solution performance was more superior at fixed volumetric flow rates of 10 ml/min and bed heights ranging from 12 cm to 36 cm But the reverse trend was observed in case of fixed bed heights of 36 cm (150 g) and variation of volumetric flow rates from 10ml/min to 30ml/min which indicates that industrial effluent performance was superior when compared to synthetic solution for heavy metal removal.

INFLUENCE OF THE REMNANT MAGNETIZATION OF THE CURRENT TRANSFORMER CORES UPON THE COMPLIANCE OF THEIR TECHNICAL CHARACTERISTICS WITH THE REQUIREMENTS FOR MICROPROCESSOR TYPE PROTECTIVE RELAYS

Work objective is finding rational technical and economic solutions for examining current transformers for techspecs compliance satisfying the requirements of reinstalled microprocessor type protective relays and automation devices manufactured by NP EKRA LLC, taking into account DC component. Research methods: analytical methods for calculating the time of remnant magnetization in the core of a current transformer. Research results and novelty: it is understood that the saturation time of current transformers of the basic and backup protections, according to the results of the analytical method, was more than 25 ms, and for current transformers of differential bus bar protection was more than 5 ms. The obtained saturation time values for all types of current transformers built into oil circuit-breaker bushings (HV line) of 110 kV and bus bar coupling connector (BCC) of 110 kV (main protection, backup protection, differential bus protection), both in the absence and in the presence of remanent induction magnetic in CT cores with three-phase and single-phase short circuits, satisfy completely technical requirements either of microprocessor type protective relays or CT differential bus bar protection. Conclusion: built into CT BCC circuit-breaker bushings of 110 kV and oil circuit-breaker bushings (HV line) of 110 kV Foundry substations do not necessitate a mandatory replacement in case of non-complex redesign of microprocessor type protective relays and automation devices. When replacing oil circuit breakers with gas-insulated ones, it is recommended to use CT with similar characteristics.

Performance Study of Absorption Tower and Adsorption Reactor to Eliminate Ammonia Gas as Pollutant

Ammonia known as harmful gas that could impact on health and environment. Typically, ammonia gas emitted by fertilizer industry, rubber factory, etc. There are many options for advance industry to control ammonia gas pollution, absorption tower using water scrubber and using activated carbon as adsorption reaction could be an option. But for middle- and lower-class industry, it is common in Indonesia, as seen on many rubber factories, ammonia gas pollution is serious problem to control, actually they have used wet scrubber but eficiency is lower about 47%. This study measure performance for ammonia elimination as gas pollutant using absorption tower and adsorption tower in laboratory scale. Using electrochemical gas sensor, we measure both ammonia concentration for inlet and outlet simultaneously to settle saturation point of these two types of ammonia emission control. In conclusion, Ammonia absorbed in water proportional to saturation time and absorbent volume. Highest absorbed ammonia concentration 1.538 mg/L on 4000 mL absorbent. For Adsorption system, saturation time proportional and correlated to adsorbent weight and Adsorption capacity reverse correlated to adsorbent weight. Optimum adsorption point can be achieved from intersection curve between saturation time and adsorption capacity which is 1200 grams adsorbent

Environmental Management: Pragmatic Suitability of Low Cost Activated Carbon in Lead (II)Ion Removal by Continuous Mode of Adsorption

Heavy metals such as chromium, lead, and arsenic are usually present in trace amounts in natural waters but many of them are toxic even at very low concentrations. An increasing quantity of heavy metals in our resources is currently an area of greater concern, especially since a large number of industries are discharging their metal containing effluents into freshwater without any adequate treatment. Activated carbons show a significant ability in removing heavy metal ions from an aqueous solution by adsorption, which has been examined by many researchers. Activated carbon derived from Manilkarazapota tree-wood (MZTWAC), which was found to be a suitable adsorbent for the removal of lead ions through continuous adsorption mode, was examined in this paper. A breakthrough curve has been plotted to find the effect of initial concentration and adsorbent bed height in the adsorption of lead (II)ion through MZTWAC. The breakthrough time and the saturation time increased as the initial concentration increased from 40 mg.L-1 to 60 mg.L-1. The saturation time was in the incremental mode when the bed height was increased from 5 cm to 7 cm bed thickness for 40 mg.L-1 concentration. Adams-Bohart’s model perfectly fits with this fixed-bed column in the removal of lead(II) from an aqueous solution using MZTWAC. Activated carbon derived from MZTWAC is better suited for the purpose of detoxifying metal-contaminated wastewater.

Kelvin-probe microscopy as a technique of estimation of the charge traps saturation time

In this work, a method for estimating the saturation time of traps in dielectric layers based on the KPM is proposed. Using hafnium oxide layers as an example, it is shown that when charging with a series of points with different durations, a different dependence of the residual potential on time is observed. It is assumed that this technique makes it possible to evaluate the performance of devices based on dielectric layers.

Modelling and simulation of the ion exchange process for Zn2+(aq) removal using zeolite NaY

The treatment of water contaminated by toxic metals using ion exchange with zeolites is becoming attractive due to its low capital costs and high potential for removal capacity. Mathematical modelling of this process allows for operational control and estimation of the ability to remove these metals. In this work, the kinetic modelling was performed based on finite bath experimental data, with Intraparticle Diffusion (IPD) and External Liquid Film Mass Transfer (MTEF) models. The models Thomas (TH), Yoon-Nelson (YN) and Solid Film Mass Transfer (MTSF) were used to estimate the saturation time, ion exchange capacity and sizing variables of a fixed bed column. For the finite bath system, the results showed that the mass transfer was better represented by the IPD phenomenon. The breakthrough curve obtained by the Aspen Adsorption (MTSF) model presented the best fit, compared with experimental data, with R2≥0.9923. The average ion exchange capacities calculated for MTSF, TH and YN were respectively 2.22, 2.12 and 2.07 meq Zn2+(aq)/ g of zeolite. The model simulated with Aspen Adsorption was also used to analyze the continuous system behaviour, by varying the height of the bed. It was observed that increasing the height, the saturation time and ion exchange capacity also increase, while reducing the height makes axial dispersion the predominant mass transfer phenomenon, which reduces the diffusion of Zn2+(aq) ions.

Analysis of the Foaming Window for Thermoplastic Polyurethane with Different Hard Segment Contents

A series of thermoplastic polyurethanes (TPUs) with different amounts of hard segments (HS) (40, 50 and 60 wt.%) are synthesized by a pre-polymer method. These synthesized TPUs are characterized by Shore hardness, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and rheology. Then, these materials are foamed by a one-step gas dissolution foaming process and the processing window that allows producing homogeneous foams is analyzed. The effect of foaming temperature from 140 to 180 °C on the cellular structure and on density is evaluated, fixing a saturation pressure of 20 MPa and a saturation time of 1 h. Among the TPUs studied, only that with 50 wt.% HS allows obtaining a stable foam, whose better features are reached after foaming at 170 °C. Finally, the foaming of TPU with 50 wt.% HS is optimized by varying the saturation pressure from 10 to 25 MPa at 170 °C. The optimum saturation and foaming conditions are 25 MPa and 170 °C for 1 h, which gives foams with the lowest relative density of 0.74, the smallest average cell size of 4 μm, and the higher cell nucleation density of 8.0 × 109 nuclei/cm3. As a final conclusion of this investigation, the TPU with 50 wt.% HS is the only one that can be foamed under the saturation and foaming conditions used in this study. TPU foams containing 50 wt.% HS with a cell size below 15 microns and porosity of 1.4–18.6% can be obtained using foaming temperatures from 140 to 180 °C, saturation pressure of 20 MPa, and saturation time of 1 h. Varying the saturation pressure from 10 to 25 MPa and fixing the foaming temperature of 170 °C and saturation pressure of 1 h results in TPU foams with a cell size of below 37 microns and porosity of 1.7–21.2%.