Search results for " absorption"

Dialysability of Calcium, Iron, and Zinc in Beans, Chick Peas, and Lentils

2002

Human artificial membranes in (bio)analytical science: Potential for in vitro prediction of intestinal absorption-A review

2021

Abstract Artificial membranes for investigation of the human absorption (oral, dermal or respiratory) of target organic compounds are aimed at mimicking the interactions occurring at and within the cell lipid membrane. Biomolecules such as proteins are also integral components of the lipid membranes and play a pivotal role towards understanding the complex mechanisms of human absorption. In this review, we will differentiate biomimetic platforms based on static (batchwise) and dynamic modes. In the former, a synthetic membrane placed between two phases (donor and acceptor) mimics a given biological system to study permeability. Parallel artificial membrane permeation assays are the most com…

Mucoadhesive Polymer Hyaluronan as Biodegradable Cationic/Zwitterionic-Drug Delivery Vehicle

2014

Mucoadhesive polymers in pharmaceutical formulations release drugs in mucosal areas. They interact and fix to mucus via molecular interpenetration, etc ., which increase drug bioavailability. Polymers physicochemical properties affect formulation mucoadhesion, rheological behaviour and drug absorption. Hyaluronan (HA) is selected as a mucoadhesive and biodegradable polymer. Geometric, topological and fractal analyses are carried out with program TOPO. Reference calculations are performed with algorithm GEPOL. Procedure TOPO underestimates molecular volume by 0.7%. Error results 5% in surface area and derived topological indices. Solvent-accessible surface is undercalculated by 3%: from hexa…

PAMPA—a drug absorption in vitro model

2004

Parallel artificial membrane permeability assay (PAMPA) was used to measure the effective permeability, P(e), as a function of pH from 4 to 10, of 17 fluoroquinolones, including three congeneric series with systematically varied alkyl chain length at the 4'N-position of the piperazine residue. The permeability values spanned over three orders of magnitude. The intrinsic permeability, P(o), and the membrane permeability, P(m), were determined from the pH dependence of the effective permeability. The pK(a) values were determined potentiometrically. The PAMPA method employed stirring, adjusted such that the unstirred water layer (UWL) thickness matched the 30-100 microm range estimated to be i…

Low-Molecular-Weight Organic Acid Complexation Affects Antimony(III) Adsorption by Granular Ferric Hydroxide.

2019

Antimony(III) mobility in natural aquatic environments is generally enhanced by dissolved organic matter. Tartaric acid is often used to form complexes with and stabilize dissolved Sb(III) in adsorption studies. However, competition between such low-molecular-weight organic acid complexation and adsorption of Sb(III) has received little attention, which prompted us to measure Sb(III) adsorption by iron oxyhydroxide adsorbents commonly used in water treatment plants. Sb K-edge X-ray absorption fine structure (EXAFS) spectra gave Sb–O and Sb–Fe distances and coordinations compatible with a bidentate binuclear inner-sphere complex with trigonal Sb(O,OH)3 polyhedra sharing corners with Fe(O,OH)…

Microwave-assisted distillation of iodine for the indirect atomic absorption spectrometric determination of iodide in milk samples

2001

To complete these microwave distillation studies, a method for iodide determination in milk-type samples is proposed. The iodide contained in the sample is oxidized to iodine, which is distilled by means of microwave energy and reduced back to iodide. This iodide is combined with Hg(II) and 2,2′-dipyridyl to give an ion pair, which is selectively extracted into IBMK. Mercury is determined in the extract by ETAAS in order to determine iodide. The yield of the distillation process (100%) was evaluated using the Sandell–Kolthoff reaction. In addition, for the solvent extraction, no buffer was needed; 3/5 was the best phase ratio (organic/aqueous); 30 s was the shaking time and the extracts wer…

Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: Effect of temperature and cosolvent on the equil…

2009

Abstract The interaction between peracetylated-β-cyclodextrin and tert-butyl and adamantyl functionalized triphenylphosphine derivatives was studied in supercritical carbon dioxide (scCO 2 ) based solvent media by UV–vis spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra both in pure carbon dioxide and in the presence of methanol as a cosolvent in the temperature range 308–323 K to estimate the internal energy and entropy of the inclusion equilibrium. The values of the equilibrium constants were found significantly smaller than those obtained in aqueous solution with analogous phosphines and substantially independent of the nature of t…

Concave π-prismand hydrocarbon [2.2.2]cyclophanes and their crystalline Ag-triflate complexes

1999

New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO2-method. The cyclophanes obtained are isomers of the very well-known [2.2.2]p,p,p-cyclophane, C24H24, a π-prismand efficiently complexing Ag+-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia[3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 ([2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag+-ion. The 16- and 17-membered [2.2.2]m,m,p- and [2.2.2]m,p,p-cyclophane (15 and 16) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as th…

The abundance of Au, Pt, Pd, and the mode of heavy metal fixation in highly polluted sediments from the Rhine River near Mainz, West Germany

1984

The Au, Pt and Pd contents of the sediments of Ginsheimer‐Altrhine River, a channel of the Rhine river which drains one of the most industrialized regions of western Europe, have been determined by flameless atomic absorption spectrophotometry. The abundances of these noble metals range from 96–460 ppb Au; 734 ppb‐31 ppm Pt and 32 ppb‐4 ppm Pd. The extremely high concentrations, particulary those of Pt and Pd, are attributed to their use in industry and are due to the formation and concentration of metal‐organic complexes, mainly at the interface between an extremely reducing and an oxidizing aquatic environment. Differential thermal analyses of the polluted sediments in comparison to the p…

Plutonium(III) complexation by humic substances studied by X-ray absorption fine structure spectroscopy

2006

Abstract We determined structural parameters for the near-neighbor surrounding of plutonium(III) in complexes with humic and fulvic acids at pH 1 and for the purpose of comparison also for the plutonium(III) aquo ion by means of X-ray absorption fine structure (XAFS) spectroscopy. It could be shown that in the complexes with humic substances as well as in the plutonium(III) aquo ion sample the trivalent oxidation state of plutonium was stable within the time of the experiment. In the humate and fulvate complexes, the plutonium(III) is surrounded by about eight oxygen atoms with an average Pu–O distance of 2.48 ± 0.02 A. The structural parameters determined for plutonium(III)–humate and –ful…