scholarly journals Drug Nanoparticle Stability Assessment Using Isothermal and Nonisothermal Approaches

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Javier Santamaría-Aguirre ◽  
Robert Alcocer-Vallejo ◽  
Mónica López-Fanárraga
Keyword(s):  
Mathematical Model ◽  
Shelf Life ◽  
Kinetic Parameters ◽  
Heterogeneous Systems ◽  
Preexponential Factor ◽  
Storage Conditions ◽  
Isoconversional Method ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Drug Products

Many drugs are administered in the form of liquid-dispersed nanoparticles. Frequently, one of the overlooked aspects in the development of this drug delivery system is the loss of efficacy and the degradation of the carried drugs. Estimating the shelf life of drug products implies the storage of samples under controlled conditions of temperature and humidity for different periods, ranging from months to years, delaying decisions during development, manufacturing, and commercialization. Adapting well-known isothermal and nonisothermal methods to nanoparticles would allow correlating kinetic parameters obtained in a single mathematical model and predicting the shelf life faster than traditional methods. Unlike the traditional approaches, the isoconversional method (i) considers drug products as heterogeneous systems, without a unique kinetic order, (ii) establishes a maximum percentage of degradation, (iii) assumes the same kinetics for all processes regardless of the conditions, and (iv) includes the influence of humidity by a modification of Arrhenius equation. This method serves in calculating the kinetic parameters and shelf life derived from them, in a few weeks. In the same way, nonisothermal treatments allow obtaining these parameters by differential scanning calorimetry. Samples are subjected to different heating rates to establish the temperature at which the thermal decomposition event occurs and, thus, to calculate in a few days the activation energy and the preexponential factor using the Kissinger method. But this approach has limitations: the isoconversional method does not consider crystalline state of the sample, while nonisothermal method ignores the effect of the storage conditions. Processing nanoparticles for isothermal and nonisothermal treatments would allow accurate and fast prediction of the drug-loaded nanoparticle shelf life correlating parameters obtained using a single mathematical model. The accuracy of the prediction would be assessed by comparison of estimated shelf life versus data coming from traditional stability studies.

scholarly journals Curing Kinetic Parameters of Epoxy Composite Reinforced with Mallow Fibers

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3939 ◽  
Author(s):  
Lucio Fabio Cassiano Nascimento ◽  
Fernanda Santos da Luz ◽  
Ulisses Oliveira Costa ◽  
Fábio de Oliveira Braga ◽  
Édio Pereira Lima Júnior ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Industrial Process ◽  
Diglycidyl Ether ◽  
Response Surfaces ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Curing Kinetic ◽  
Technological Tool

Knowledge about the curing behavior of a thermosetting resin and its composites includes the determination of kinetic parameters and constitutes an important scientific and technological tool for industrial process optimization. In the present work, the differential scanning calorimetry (DSC) technique was used to determine several curing parameters for pure epoxy and its composite reinforced with 20 vol % mallow fibers. Analyses were performed with heating rates of 5, 7.5, and 10 °C/min, as per the ASTM E698 standard. The kinetic related parameters, that is, activation energy (E), Avrami’s pre-exponential factor (Z), and mean time to reach 50% cure (t½), were obtained for the materials, at temperatures ranging from 25 to 100 °C. Response surfaces based on the mathematical relationship between reaction time, transformed fraction, and temperature were provided for optimization purposes. The results showed that the average curing time used for the production of diglycidyl ether of bisphenol A/triethylenetetramine (DGEBA/TETA) epoxy systems or their composites reinforced with natural mallow fibers can be considerably reduced as the temperature is increased up to a certain limit.

scholarly journals Holistic Approach to the Uncertainty in Shelf Life Prediction of Frozen Foods at Dynamic Cold Chain Conditions

Foods ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 714 ◽  
Author(s):  
Maria Giannakourou ◽  
Petros Taoukis
Keyword(s):  
Shelf Life ◽  
Kinetic Parameters ◽  
Holistic Approach ◽  
Storage Conditions ◽  
Life Assessment ◽  
Cold Chain ◽  
Stochastic Algorithm ◽  
Real Distribution ◽  
Prediction Scheme ◽  
Calculated Parameter

Systematic kinetic modeling is required to predict frozen systems behavior in cold dynamic conditions. A one-step procedure, where all data are used simultaneously in a non-linear algorithm, is implemented to estimate the kinetic parameters of both primary and secondary models. Compared to the traditional two-step methodology, more precise estimates are obtained, and the calculated parameter uncertainty can be introduced in realistic shelf life predictions, as a tool for cold chain optimization. Additionally, significant variability of the real distribution/storage conditions is recorded, and must be also incorporated in a kinetic prediction scheme. The applicability of the approach is theoretically demonstrated in an analysis of data on frozen green peas Vitamin C content, for the calculation of joint confidence intervals of kinetic parameters. A stochastic algorithm is implemented, through a double Monte Carlo scheme incorporating the temperature variability during distribution, drawn from cold chain databases. Assuming a distribution scenario of 130 days in the cold chain, 93 ± 110 days remaining shelf life was predicted compared to 180 days assumed based on the use by date. Overall, through the theoretical case study investigated, the uncertainty of models’ parameters and cold chain dynamics were incorporated into shelf life assessment, leading to more realistic predictions.

Ammonium Perchlorate Decomposition Characteristic Parameters Determination, a Simplified Approach

2011 ◽  
Vol 110-116 ◽  
pp. 155-162 ◽  
Author(s):  
W. M. Abdel-Wareth ◽  
Xu Xu
Keyword(s):  
Kinetic Parameters ◽  
Ammonium Perchlorate ◽  
Isoconversional Method ◽  
Nitrogen Atmosphere ◽  
Characteristic Parameters ◽  
Heating Rates ◽  
Exponential Factor ◽  
Simplified Approach ◽  
Surface Areas ◽  
Bet Method

Effects of various grain sizes (10~390 µm) under heating rate of 40 °C/min on ammonium perchlorate (AP) decomposition characteristic parameters, the decomposition thermal behavior and kinetic parameters (activation energy and pre-exponential factor), were investigated by simultaneous DSC/TGA in a dynamic nitrogen atmosphere. In addition, the specific surface areas were measured by the BET-method. Moreover, the kinetic parameters were determined by a simplified approach based on the isoconversional method. The results showed that, the higher the AP particle size the lower the determined decomposition kinetic parameters. In addition, the results were in acceptable agreements with some important literatures. Moreover, it was highly recommended to apply the higher agreeable heating rates for AP samples to determine that parameters more accurately.

scholarly journals Non-Isothermal Crystallization Kinetic of Polyethylene/Carbon Nanotubes Nanocomposites Using an Isoconversional Method

2019 ◽  
Vol 3 (1) ◽  
pp. 21 ◽  
Author(s):  
Beatriz Menezes ◽  
Tiago Campos ◽  
Thais Montanheiro ◽  
Renata Ribas ◽  
Luciana Cividanes ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Kinetic Parameters ◽  
Isothermal Crystallization ◽  
Crystallization Kinetic ◽  
Model Fitting ◽  
Kinetic Studies ◽  
Isoconversional Method ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Crystallite Sizes

Behavior studies of thermoplastic polymers during non-isothermal crystallization are extremely important since most of their properties are influenced by degree of crystallinity and the crystallization process. In general, an approach based on a model-fitting method is used to perform crystallization kinetic studies. Due to their inability to uniquely determine the reaction mode, many studies have used the isoconversional method, where it is not necessary to assume a crystallization model to obtain the kinetic parameters. Therefore, in this work, the influence of acid and octadecylamine functionalized carbon nanotubes (CNTs) in the crystallization kinetic of polyethylene (PE) was studied using an isoconversional method with differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The kinetic parameters and the crystallization model were determined. The incorporation of functionalized and non-functionalized CNTs into PE did not change the Johnson-Mehl-Avrami crystallization model. However, the CNTs increased the crystallization temperature and reduced the activation energy for crystallization. In addition, the Avrami coefficient values were lower for the nanocomposites when compared to pure PE. The incorporation of CNTs accelerated the crystallization of PE, reducing the crystallite sizes and modifying their morphology.

Kinetic study of wood chips decomposition by TGA

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Lukáš Gašparovič ◽  
Zuzana Koreňová ◽  
Ľudovít Jelemenský
Keyword(s):  
Activation Energy ◽  
Kinetic Parameters ◽  
Isoconversional Method ◽  
Nitrogen Atmosphere ◽  
Decomposition Process ◽  
Wood Chips ◽  
Water Evaporation ◽  
Heating Rates ◽  
Exponential Factor ◽  
Decomposition Processes

AbstractPyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C for four heating rates: 2 K min−1, 5 K min−1, 10 K min−1, and 15 K min−1. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds.

scholarly journals Calculation of Kinetic Parameters of Thermal Decomposition of Forest Waste using the Monte Carlo Technique

2020 ◽  
Vol 24 (1) ◽  
pp. 162-170
Author(s):  
Alok Dhaundiyal ◽  
Laszlo Toth
Keyword(s):  
Activation Energy ◽  
Monte Carlo ◽  
Kinetic Parameters ◽  
Preexponential Factor ◽  
Thermal Conversion ◽  
Inert Atmosphere ◽  
Monte Carlo Technique ◽  
Heating Rates ◽  
Forest Waste ◽  
Distribution Parameters

AbstractThis paper deals with the pyrolysis of forest waste in the presence of an inert atmosphere. Experiments are carried out at different heating rates (5 °C, 10 °C and 15 °C) to determine derivative thermogravimetric behaviour of the material. Unlike the conventional scheme, the Monte Carlo technique is implemented to solve the distributed activation energy model (DAEM). DAEM is transformed into the inverse pyrolysis problem to determine the kinetic parameters of thermal degradation of forest waste. Activation energy, the preexponential factor and the distribution parameters are estimated by introducing the Monte Carlo Technique in the thermal conversion process.

scholarly journals Curing kinetics of two commercial urea-formaldehyde adhesives studied by isoconversional method

2011 ◽  
Vol 65 (6) ◽  
pp. 717-726 ◽  
Author(s):  
Mladjan Popovic ◽  
Jaroslava Budinski-Simendic ◽  
Mirjana Jovicic ◽  
Joszef Mursics ◽  
Milanka Djiporovic-Momcilovic ◽  
...  
Keyword(s):  
Activation Energy ◽  
Urea Formaldehyde ◽  
Curing Kinetics ◽  
Isoconversional Methods ◽  
Isoconversional Method ◽  
Reaction Enthalpy ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Kinetics Of

Differential scanning calorimetry (DSC) was used to evaluate the curing kinetics of two commercial urea-formaldehyde (UF) adhesives having different formaldehyde to urea (F/U) ratio of 1.112 (UF1) and 1.086 (UF2). DSC measurements were done in dynamic scanning regime with heating rates of 5, 10, 15 and 20?C?min-1 in order to determine the activation energy for each adhesive. Obtained data were analyzed using isoconversional methods with application of Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose kinetic models. In addition, different catalyst levels were tested at the heating rate of 10?C/min. Results showed that the adhesive with higher F/U ratio achieved higher activation energy, while having lower peak temperature of curing reaction. It was also noticed that the increase of catalyst level influenced the increase of reaction enthalpy of the adhesive with lower F/U ratio.

Improving Wire Sweep Performance by Measuring Degree of Cure of Epoxy Mold Compounds

2011 ◽  
Author(s):  
Sheila Liza B. Dal
Keyword(s):  
Differential Scanning Calorimetry ◽  
Shelf Life ◽  
Trial And Error ◽  
Active Components ◽  
Scanning Calorimetry ◽  
Degree Of Cure ◽  
Electronic Package ◽  
Viscosity Changes ◽  
Epoxy Mold Compounds

Abstract The choice of epoxy mold compound (EMC) for an electronic package is based mostly on how much protection it provides to the active components in the package. But the choice is not a straightforward process. Rather it is mostly trial and error using different assembly parameters to find the most robust material while assembly defects are monitored. One such defect associated to EMC processing is wire sweep, and many studies have shown that it is mainly caused by viscosity changes in the EMC. In this study, samples of EMC in various stages of shelf life and staging times were analyzed for degree of cure using a method called differential scanning calorimetry (DSC). Samples are then processed at assembly for wire sweep measurement. It was found out that degree of cure increases with staging time at different rates for each shelf life. It was also found out that wire sweep did not only increase with degree of cure but it was also found to be predictable with respect to the latter. Using this information, the age and staging limit for each material was identified that would not cause wire sweep issues.

scholarly journals Investigation of the Physical, Chemical and Microbiological Stability of Losartan Potassium 5 mg/mL Extemporaneous Oral Liquid Suspension

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 301
Author(s):  
Lisa Foley ◽  
Jennifer Toney ◽  
James W. Barlow ◽  
Maura O’Connor ◽  
Deirdre Fitzgerald-Hughes ◽  
...  
Keyword(s):  
Shelf Life ◽  
Storage Conditions ◽  
Losartan Potassium ◽  
Microbial Count ◽  
E Coli ◽  
Physical Chemical ◽  
Liquid Suspension ◽  
Oral Liquid ◽  
Microbiological Stability ◽  
Stability Data

Extemporaneous oral liquid preparations are commonly used when there is no commercially available dosage form for adjustable dosing. In most cases, there is a lack of stability data to allow for an accurately assigned shelf life and storage conditions to give greater confidence of product safety and efficacy over its shelf life. The aim of this study was to evaluate the physical, chemical and microbiological stability of an extemporaneous oral liquid suspension of losartan potassium, 5 mg/mL, used to treat paediatric hypertension in Our Lady’s Children’s Hospital Crumlin, Ireland. The losartan content of extemporaneous oral suspensions, prepared with and without addition of water, was measured by UV and confirmed by HPLC analysis. Suspensions were stored at 4 °C and room temperature (RT) and were monitored for changes in; pH, colour, odour, re-dispersibility, Total Aerobic Microbial Count, Total Yeast and Mould Count and absence of E. coli. Results showed that suspensions prepared by both methods, stored at 4 °C and RT, were physically and microbiologically stable over 28 days. Initial losartan content of all suspensions was lower than expected at 80–81% and did not change significantly over the 28 days. HPLC and NMR did not detect degradation of losartan in the samples. Suspensions prepared in water showed 100% losartan content. The reduced initial losartan content was confirmed by HPLC and was related to the acidic pH of the suspension vehicle. Physiochemical properties of the drug are important factors for consideration in the selection of suspension vehicle for extemporaneous compounding of oral suspensions as they can influence the quality, homogeneity and efficacy of these preparations.

scholarly journals Proof-of-Concept of Detection of Counterfeit Medicine through Polymeric Materials Analysis of Plastics Packaging

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2185
Author(s):  
Mohammad Salim ◽  
Riyanto Teguh Widodo ◽  
Mohamed Ibrahim Noordin
Keyword(s):  
Polymeric Materials ◽  
Proof Of Concept ◽  
Scanning Calorimetry ◽  
Counterfeit Drug ◽  
Drug Products ◽  
Counterfeit Medicines ◽  
Counterfeit Medicine ◽  
Counterfeit Pharmaceuticals ◽  
Purge Gas ◽  
Sample Set

The detection of counterfeit pharmaceuticals is always a major challenge, but the early detection of counterfeit medicine in a country will reduce the fatal risk among consumers. Technically, fast laboratory testing is vital to develop an effective surveillance and monitoring system of counterfeit medicines. This study proposed the combination of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Differential Scanning Calorimetry (DSC) for the quick detection of counterfeit medicines, through the polymer analysis of blister packaging materials. A sample set containing three sets of original and counterfeit medicine was analyzed using ATR-FTIR and DSC, while the spectra from ATR-FTIR were employed as a fingerprint for the polymer characterization. Intending to analyze the polymeric material of each sample, DSC was set at a heating rate of 10 °C min−l and within a temperature range of 0- 400 °C, with nitrogen as a purge gas at a flow rate of 20 ml min−an. The ATR-FTIR spectra revealed the chemical characteristics of the plastic packaging of fake and original medicines. Further analysis of the counterfeit medicine’s packaging with DSC exhibited a distinct difference from the original due to the composition of polymers in the packaging material used. Overall, this study confirmed that the rapid analysis of polymeric materials through ATR-FTIR and comparing DSC thermograms of the plastic in their packaging effectively distinguished counterfeit drug products.

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