Solid State Testing of Inhaled Formulations
Anthony J. Hickey, Sandro R.P. da Rocha in Pharmaceutical Inhalation Aerosol Technology, 2019
The most common selective and sensitive method for water content determination is Karl Fischer coulometric titration (MacLeod 1991). The principle of operation involves a reaction of water with iodine and sulfur dioxide in the presence of an alcohol (e.g. methanol) and an organic base (e.g. imidazole). Automated instruments and reagents containing all the necessary chemicals offer convenience and simplify the operation of the titration. The reagent is kept in a tightly sealed reaction cell with a large anode and a small cathode that conducts an electrical current through the cell. Iodine is generated by electrolysis by the anode and reacts with the water in the reagent. The reaction consumes water stoichiometrically until no more water is present (MacLeod 1991, British Pharmacopoeia 2017, European Pharmacopoeia 2017, United States Pharmacopeia 40-National Formulary 35 2017). There will then be an excess of iodine, which is detected by a change in the electrical conductivity in the cell, signifying the titration end point. The electrical current needed to generate the iodine during the titration is used to calculate the amount of water present (MacLeod 1991, British Pharmacopoeia 2017, European Pharmacopoeia 2017, United States Pharmacopeia 40-National Formulary 35 2017).
Using iodine for analysis
Tatsuo Kaiho in Iodine Made Simple, 2017
Starch is a glucose polymer (d-glucose) comprises of approximately 20% liner polymer amylose and 80% amylopectin polymers with many branches. In the iodine-starch reaction, amylose molecules in the starch form a helical structure in the aqueous solution and turn bluish purple-reddish brown when iodine molecules are present. When the colored solution is heated, the iodine molecules are released from the helical structure, and the solution becomes colorless. However, when cooled, the helical structure is restored as iodine molecules return, and the solution regains its color. The iodine-starch reaction is well used in the educational field, and is always quoted in elementary, junior high, and high school science, chemistry and biology textbooks, as well as in food science textbooks. The iodine-starch reaction is used to verify the existence of starch from photosynthesis in plants leaves and to track the digestion and decomposition of starch by digestive enzymes. In addition, iodine plays a vital role in analytical chemistry. For example, the iodine titration is a typical titration method in volumetric analysis along with neutralization titration, oxidization–reduction titration, and precipitation titration [25].
Solution Concentration, Molarity, and Solution Stoichiometry
Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk in Survival Guide to General Chemistry, 2019
Titration is an experimental technique to measure the (unknown) amount of one reactant, which is required to exactly react with a known amount of another reactant. The measurement then allows a calculation for the original amount of moles or mass or concentration of the unknown reactant. The experiment often uses an indicator, which identifies the point at which both reactants are present in the exact molar ratio required by the balanced equation, termed the stoichiometric equivalence point; this can be the neutralization point for certain acid/base reactions.
Discovery of antimicrobial compounds targeting bacterial type FAD synthetases
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
María Sebastián, Ernesto Anoz-Carbonell, Begoña Gracia, Pilar Cossio, José Antonio Aínsa, Isaías Lans, Milagros Medina
ITC experiments were performed to characterise the protein’s affinity for the selected compounds, as also the thermodynamic parameters that drive the interaction. Experiments were carried out in an AutoITC200 (MicroCal) thermostated at 25 °C. In these experiments, ∼400 µM of each compound were used to titrate ∼25 µM CaFADS contained in a 200 µL cell. However, when saturation of the protein was not reached, higher concentrations of compounds were employed. The titrations were performed by stepwise injections of the titrating compound. Up to 19 injections of 2 µl were added to the cell sample and mixed using a 1000 rpm stirrer syringe. The compounds and the protein were dissolved in 20 mM PIPES, pH 7.0, 10 mM MgCl2 and degassed prior to titration. DMSO was added to the protein and ligand samples, until reach a final concentration of 3%. The association constant (Ka), the enthalpy variation (ΔH) and the binding stoichiometry (N), were obtained through non-lineal regression of the data to a model for one or two independent binding sites, implemented in Origin 7.0 (OriginLab) as previously described27,29. The entropic contribution (−TΔS), the Gibbs free energy (ΔG) and the dissociation constant (Kd) were obtained through essential thermodynamic equations.
Curcumin-loaded microemulsion: formulation, characterization, and in vitro skin penetration
Published in Drug Development and Industrial Pharmacy, 2023
Irene Carolina Luna-Canales, Norma Laura Delgado-Buenrostro, Yolanda I. Chirino, Guadalupe Nava-Arzaluz, Elizabeth Piñón-Segundo, Graciela Martínez-Cruz, Adriana Ganem-Rondero
It has been reported that the first ME was prepared in 1928, but it was not until 1958 that MEs are known under this name. Since then, MEs have found application in a wide range of fields [35]. The formulation of a ME implies:The selection of possible components (i.e. surfactant, co-surfactant, oil, and aqueous phase). This can be carried out through drug solubility studies.The construction of pseudo-ternary diagrams, which allows defining ME formation zones. Through this diagram, it is possible to determine the relative amount of ME components, and thus the optimized formulation can be found out. The phase titration method is one of the methods proposed for ME preparation. In this method, mixtures of oil, surfactant, and cosurfactant in different proportions, are titrated with distilled water until the mixture becomes a ME. In this work, the selected components were oleic acid as an oily phase, Tween® 80 as a surfactant, and Transcutol® HP as a co-surfactant. Three surfactant:co-surfactant ratios (1:1, 1:2, and 2:1) were tested to build the pseudo-ternary diagrams. The systems with transparent or translucent appearance and low viscosity were recorded as MEs.
Protective effects of a standardized extract (HemoHIM) using indomethacin- and ethanol/HCl-induced gastric mucosal injury models
Published in Pharmaceutical Biology, 2019
Da-Ae Kwon, Yong Sang Kim, Sin Hwa Baek, Seul-Ki Kim, Hyun Kyu Kim, Sung-Kee Jo, Uhee Jung, Hae-Ran Park, Hak Sung Lee
Rats were divided into five groups: control, EtOH/HCl, HemoHIM 250 mg kg−1, HemoHIM 500 mg kg−1, and cimetidine 100 mg kg−1. HemoHIM (250 or, 500 mg kg−1) dissolved in 0.5% CMC or cimetidine (100 mg kg−1) dissolved in 20% Tween 80, were administered orally after 24 h of fasting. Next, 60% EtOH/150 mM HCl was administered orally 1 h after the administration of HemoHIM or cimetidine. One hour after administration of 60% EtOH/150 mM HCl, rats were dissected. The gastric juice was centrifuged at 3,000 rpm for 20 min and the total acidity was assayed (Nam et al. 2014). Briefly, 0.5% dimethylaminobenzene alcohol solution and 1% phenolphthalein alcohol solution were added to the gastric juice supernatant. The solution was titrated by adding 0.1 N NaOH solution until the red color disappeared. The total acidity of the titration value is expressed as meq/L/100 g using the following formula: Acidity = (Volume of NaOH × Normality of NaOH × 100)/0.1 (meq/L).
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