Ultrafiltration Through Collodion Membranes

Abstract

It is obvious that the factors considered in this paper render data obtained by ultrafiltration open to criticism unless they are checked by other methods and precautions are taken for the elimination of the vitiating effects which have been described. As regards the mechanism of ultrafiltration, the view of a sieve-like action as most experimental evidence indicates, is adequate, if all the factors are considered which might modify the effective pore size. The behaviors of collodion membranes which seem contrary to a mechanism of ultrafiltration based on the existence of a system of pores, can be explained on the basis of a variable layer of adsorbed fluid on the walls of the pores. It is, therefore, unsound to make any deductions about living tissues from the demonstration of changes produced in the behavior of collodion membranes. Thus, the increase in the rate of filtration of water through collodion by diuretics (29) or the change of permeability due to the presence of surface-active materials, gives us no information about their action in the living organism. The effect of these substances on a sieve-like membrane of the type of collodion would not necessarily bear any analogy to that exerted on the emulsion type of membrane of living cells. The mechanisms of the reactions necessary to produce the same effects in such widely differing systems may be entirely unrelated.

Application of Ion-Pair Methods to Drug Extraction from Biological Fluids II: Quantitative Determination of Biguanides in Biological Fluids and Comparison of Protein Binding Estimates

“…the estimated protein binding in human plasma (Table 1V) by metformin, buformin, and phenformin was 7.4, 7.7, and 12%, respectively. These lower values confirmed the argument (7,8) that complete filtration of drug-spiked plasma tends to overestimate the extent of protein binding because the complete protein precipitation in the filter cone traps and inhibits the free passage of other soluble plasma components.…”

“…Thus, the estimated extent of protein binding would be 20% for phenformin, 24% for buformin, and 20% for metformin when the plasma is completely filtered. It has been argued(7,8) that this procedure tends to overestimate protein binding since complete filtration of plasma protein with precipitation in the cone from a substrate-containing plasma has been claimed to trap and inhibit the free passage of other soluble plasma components. Part of the background reading is attributable to the new ultrafiltration cone used.…”

Pharmacokinetics of β-Methyldigoxin in Healthy Humans I: Intravenous Studies

“…and filtered at 1200 rpm for 18-20 min in a centrifugelY through two to four high flux cone membranes20. Half-filtration was preferred, since complete filtration of plasma might trap and inhibit the free passage of other soluble plasma components (10)(11)(12). Total drug concentration (bound and unbound) in the plasma prior to filtration and the free drug concentration in the plasma water of the filtrate were determined by liquid scintillation spectrophotometry.…”

Oberflächenmodifizierung von Wasseraufbereitungsmembranen

“…Grollman diskutierte die Wirkung der Proteinadsorption auf die Permeanz von Kollodium‐Membranen und stellte fest, dass adsorbierte Proteine die effektive Porengröße und die Membranpermeabilität verringerten. Nicht zuletzt erwähnte er auch, dass hydrophile Adsorber (wie etwa Proteine) stark Wasser an die Membran binden . Während Grollman darlegte, dass diese Lösungsmitteladsorption die effektive Porengröße der Membranen weiter verringern würde, bildet die Erkenntnis, dass Wasser über eine intermediäre, hydrophile Substanz stärker an Membranen gebunden werden kann, die Grundlage für viele der heute verwendeten Strategien zur Oberflächenmodifizierung zur Abschwächung von Fouling.…”