scholarly journals Application of RP-18 TLC Retention Data to the Prediction of the Transdermal Absorption of Drugs

2021 ◽  
Vol 14 (2) ◽  
pp. 147
Author(s):  
Anna W. Sobańska ◽  
Jeremy Robertson ◽  
Elżbieta Brzezińska
Keyword(s):  
Surface Area ◽  
Phosphate Buffer ◽  
Permeability Coefficient ◽  
Electronic Energy ◽  
Skin Permeability ◽  
Log P ◽  
Retention Data ◽  
Independent Variables ◽  
Model Based ◽  
Chromatographic Parameters

Several chromatographic parameters (RM0 and S obtained from RP-18 TLC with methanol—pH 7.4 phosphate buffer mobile phases by extrapolation to zero concentration of methanol; Rf and RM obtained from RP-18 TLC with acetonitrile—pH 7.4 phosphate buffer 70:30 v/v as a mobile phase) and calculated molecular descriptors (molecular weight—MW; molar volume—VM; polar surface area—PSA; total count of nitrogen and oxygen atoms—(N+O); H-bond donor count—HD; H-bond acceptor count—HA; distribution coefficient—log D; total energy—ET; binding energy—Eb; hydration energy—Eh; energy of the highest occupied molecular orbital—EHOMO; energy of the lowest unoccupied orbital—ELUMO; electronic energy—Ee; surface area—Sa; octanol-water partition coefficient—log P; dipole moment—DM; refractivity—R, polarizability—α) and their combinations (Rf/PSA, RM/MW, RM/VM) were tested in order to generate useful models of solutes’ skin permeability coefficient log Kp. It was established that neither RM0 nor S obtained in the conditions used in this study is a good predictor of the skin permeability coefficient. The chromatographic parameters Rf and Rf/PSA were also unsuitable for this purpose. A simple and potentially useful, purely computational model based on (N+O), log D and HD as independent variables and accounting for ca. 83% of total variability was obtained. The evaluation of parameters derived from RM (RM, RM/MW, RM/VM) as independent variables in log Kp models proved that RM/VM is the most suitable descriptor belonging to this group. In a search for a reliable log Kp model based on this descriptor two possibilities were considered: a relatively simple model based on 5 independent variables: (N+O), log D, RM/VM, ET and Eh and a more complex one, involving also Eb, MW and PSA.

scholarly journals Gradient HPLC in the determination of drug lipophilicity and acidity

2001 ◽  
Vol 73 (9) ◽  
pp. 1465-1475 ◽  
Author(s):  
Roman Kaliszan ◽  
Piotr Haber ◽  
Tomasz Baczek ◽  
Danuta Siluk
Keyword(s):  
Mobile Phase ◽  
High Performance ◽  
Standard Procedure ◽  
Gradient Elution ◽  
Log P ◽  
Retention Data ◽  
Organic Modifier ◽  
Wide Range ◽  
Aqueous Component ◽  
Initial Ph

The linear-solvent strength (LSS) model of gradient elution in high-performance liquid chromatography (HPLC) has been demonstrated to provide parameters of lipophilicity and acidity of analytes. pKa and log kw values are determined in three gradient runs. The first two experiments use an aqueous buffered eluent with a wide-range organic modifier gradient at pH of buffer, providing suppression of ionization of the analyte. That experiment allows an estimate of contents of the organic modifier in the mobile phase (%B), producing requested retention coefficient, k, for the nonionized form of the analyte. The next experiment is carried out with the latter %B and a pH-gradient of the aqueous component of the eluent that is sufficient to overlap possible pKa value of the analyte. The initial pH of the buffer used to make the mobile phase is selected to insure that the analyte is in nonionized form. The resulting retention time allows an estimate of pKa in a solvent of the given %B.The log kw parameter obtained correlated well with the corresponding value obtained by the standard procedure of extrapolation of retention data determined in a series of isocratic measurements. The correlation between log kw and the reference parameter of lipophilicity, log P, was very good for a series of test analytes. The values of pKa were found to correlate with the literature pKa data determined in water for a set of aniline derivatives studied.

scholarly journals Modelos alométricos na determinação da área foliar de Bauhinia monandra Kurz

2016 ◽  
Vol 7 (3) ◽  
pp. 415
Author(s):  
Edilson Romais Schmildt ◽  
Omar Schmildt ◽  
Rodrigo Sobreira Alexandre ◽  
Adriano Alves Fernandes ◽  
Marcio Paulo Czepak
Keyword(s):  
Mathematical Models ◽  
Leaf Area ◽  
Linear Model ◽  
Potential Model ◽  
Leaf Surface ◽  
Linear Quadratic ◽  
Potential Models ◽  
Independent Variables ◽  
Model Based ◽  
Area Determination

The aim of this study was to evaluate the efficiency of the adjustment of mathematical models for determining Bauhinia monandra leaf area using the length and/or width of the leaves as independent variables. Leaves from plants with three years were used to the estimative of equations in linear, quadratic and potential models. The validation from the estimated leaf area as a function of the observed leaf area showed that the linear model based on the product of length and width of the largest leaf surface is the model that best fits. However, the leaf area determination can be represented by using only the length or width of the leaves with little loss of accuracy. A representation that better estimates Bauhinia monandra leaf area with easy application is the potential model in which xi represents the length of one of the symmetrical leaf lobes.

Cell osmotic water permeability of isolated rabbit proximal straight tubules

1982 ◽  
Vol 242 (4) ◽  
pp. F321-F330 ◽  
Author(s):  
E. Gonzalez ◽  
P. Carpi-Medina ◽  
G. Whittembury
Keyword(s):  
Surface Area ◽  
Water Flow ◽  
Water Permeability ◽  
Permeability Coefficient ◽  
Osmotic Water Permeability ◽  
Water Permeability Coefficient ◽  
Osmotic Water ◽  
Straight Tubules ◽  
Tubular Surface ◽  
Set Up

Proximal straight tubules were dissected and mounted in a chamber with their lumina occluded. The well-stirred bath could be 95% changed within 84 ms to set up osmotic gradients (delta Coi) across the peritubular cell aspect. Volume changes (less than or equal to 10 pl/mm) were estimated from continuous records of diameter changes (error less than 0.1 micrometers). delta Coi greater than or equal to 2-3 mosM could be discerned. delta Coi values from 10 to 44 mosM were used to evaluate Posc, the cell osmotic water permeability coefficient, and extrapolated to delta Coi = 0. Posc = 25.1 (+/- 2.3) X 10(-4) cm3.s-1.osM-1.cm2 tubular surface area-1. These values are lower than those reported for Pose, the transepithelial osmotic water permeability coefficient, and become lower if corrected for the real (infolded) peritubular cell surface area. Thus, for a given osmotic difference, transcellular water flow finds a higher resistance than paracellular water flow. Experiments were also performed with delta Coi greater than 100 mosM, but interpretation of these data is difficult because of the presence of volume regulatory phenomena and other undesirable effects.

Oxygen and carbon dioxide permeability of subcutaneous pockets

1962 ◽  
Vol 202 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Hugh D. Van Liew
Keyword(s):  
Carbon Dioxide ◽  
Blood Flow ◽  
Surface Area ◽  
Uptake Rate ◽  
Permeability Coefficient ◽  
Exchange Coefficient ◽  
Adjacent Tissue ◽  
Permeability Coefficients ◽  
Tissue Tension

Uptake rate of a gas from a rat's subcutaneous gas pocket was divided by the surface area and by the apparent pocket-to-tissue tension difference to yield an exchange coefficient, K'. Values in (ml x 10–4)/(min cm2 atm) were O2, 6.6; CO2, 150; and N2, 2. Blood flow in adjacent tissue appeared to have little influence on uptakes of O2 and CO2, since the K'co2:K'o2 ratio indicated that the uptakes were governed by diffusion alone, and drastic alteration of blood flow (death of the animal) decreased K'o2 by only 10%. In contrast, blood flow apparently affected N2 uptake. Because O2 and CO2 uptakes were not blood flow limited, K'o2 and K'co2 are estimates of true permeability coefficients; the calculated permeability coefficient for N2 is 3.3 (ml x 10–4)/(min cm2 atm). Comparison shows the pocket surface to be 1/50–1/150 as effective for O2 transfer as the lung. Finally, corrections are calculated for pocket-to-tissue pO2 and pCO2 differences in gas pockets used for tissue tonometry.

Optimal Decolorization Efficiency of Reactive Red 3 by Fe-RH-MCM-41 Catalytic Wet Oxidation Coupled with Box-Behnken Design

2013 ◽  
Vol 545 ◽  
pp. 109-114 ◽  
Author(s):  
Kitirote Wantala ◽  
Pongsert Sriprom ◽  
Nusavadee Pojananukij ◽  
Arthit Neramittagapong ◽  
Sutasinee Neramittagapong ◽  
...  
Keyword(s):  
Surface Area ◽  
Hexagonal Lattice ◽  
Hexagonal Structure ◽  
Bet Surface Area ◽  
Molar Ratio ◽  
Wet Oxidation ◽  
Catalytic Wet Oxidation ◽  
Box Behnken Design ◽  
Independent Variables ◽  
Mcm 41

The reactive red 3 was degraded by catalytic wet oxidation process over Fe-RH-MCM-41 prepared by Direct Hydrothermal Technique (DHT) at Si/Fe molar ratio of 10 using silica from rice husk. The extended reaction conditions were studied as a function of reaction temperatures, initial H2O2 concentrations and initial pH of solutions designed by Box-Behnken design (BBD) based on Response Surface Methodology (RSM) to achieve the optimal condition and interaction of independent variables. The characterizations of catalyst were studied by XRD, BET surface area and TEM to explain the morphology of surface and to confirm the hexagonal structure. The results showed the 2theta peak can be indexed to hexagonal lattice that also confirmed by TEM result and surface area about 650 m2/g. All of independent variables showed significant on the degradation of reactive red 3 except for initial H2O2 concentration.

Enzymatic burn wound debridement with NexoBrid®: Cost simulations and investigations on cost efficiency

2017 ◽  
Vol 23 (01) ◽  
pp. 21-28 ◽  
Author(s):  
Monika A. Kern ◽  
Norbert von Depka ◽  
Christian Schackert ◽  
Wolfgang Henkel ◽  
Christoph R. Hirche
Keyword(s):  
Surface Area ◽  
Wound Care ◽  
Treatment Costs ◽  
Burn Wound ◽  
Treatment Pathways ◽  
Drg System ◽  
Model Based ◽  
Pricing System ◽  
Patient Model ◽  
Enzymatic Debridement

Abstract Aim Removal of eschar (debridement) is an essential and early step in the treatment of deep burns. Enzymatic debridement by NexoBrid® is a relatively new non-surgical tool for early, individualized and selective debridement which adds some advantages compared to surgical standard techniques known as standard of care (SOC). Nevertheless, until now it is not represented and calculated in the pricing system for German hospitals (G-DRG system), and an own operative procedure key (OPS) is lacking. The objective of this empiric cost study was to compare treatment cost of enzymatic debridement by NexoBrid® and SOC based procedures and to analyse the impact of improved burn wound care using NexoBrid® on total treatment costs of burn patients. Method The analysis is based on two different cost simulation models, the Average Outcome Model and the Defined Patient Model. Based on the results of a randomized phase III trial and treatment costs specified in the pricing system for German hospitals (G-DRG system), total costs of NexoBrid® based treatments were compared to those of SOC to determine cost saving potentials (Average outcome model). In addition, distinct burn wound treatment pathways common in clinical practice were assigned to actual treatment costs to allow economic considerations (Defined Patient Model). Results Using NexoBrid® cost savings are inversely related to the treated total burned surface area (1–15% TBSA) and directly related to the savings in burn centre stay (up to 6.5 days) (Average Outcome Model). Based on quantitative and qualitative aspects, three quarter of all cases in the range of 5% to 15% TBSA burned are in favour of NexoBrid®. Main cost drivers are LOS and ICU stay (45–80% of total costs). NexoBrid® becomes a more powerful cost driver with increasing TBSA treated. If NexoBrid® completely substitutes for SOC, the total cost per patient can be reduced by nearly 30% (treatment of 5% TBSA) or are in the range of SOC costs (treatment of 15% TBSA) (Defined Patient Model). Highest costs are generated when enzymatic and surgical methods for debridement are combined and an increased LOS or ICU stay is indicated. Conclusion Cost advantages of enzymatic debridement by NexoBrid® may emerge in cases with low or medium burned and treated surface area when costs for enzymatic debridement remain below the costs for SOC (excision plus autografting). Even in more severe cases (15% TBSA burned) total costs of basic NexoBrid®-based treatment pathways do not exceed costs of comparable SOC pathways. In addition, enzymatic debridement by NexoBrid® can be successfully applied as a strategic tool in order to reduce surgical procedure time and OR room capacity and making use of the redundant capacity for further surgical cases reimbursement. Beside these quantitative aspects that may improve overall economic efficiency, qualitative improvements of burn wound care must be considered separately from this analysis.

Preparation of amorphous aluminium ammonium phosphates

2012 ◽  
Vol 1373 ◽  
Author(s):  
Barbara Grzmil ◽  
Kinga Łuczka ◽  
Marta Gleń
Keyword(s):  
Chemical Composition ◽  
Physicochemical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Process Parameters ◽  
Research Process ◽  
Molar Ratio ◽  
Oil Absorption ◽  
Independent Variables ◽  
Statistical Program

ABSTRACTA method for obtaining of amorphous aluminium ammonium phosphates is developed. The statistical program STATISTICA 9 is used for planning and evaluation of the experiments. Research is carried out according to the Box-Behnken model for the following values of independent variables (input factors): pH: 6.0 ± 2; concentration of reagents: 40 ± 10 wt%, molar ratio of NH4+:PO43- in substrates (2 ± 1:1) i.e. Al3+:NH4+:PO43- (0.66:1-3:1). On the basis of this research, process parameters are determined, in which materials with the expected physicochemical properties (chemical composition, specific surface area, oil absorption number) can be obtained.

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