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PubMed2004

Removal of hepatitis A virus from water by polyacrylonitrile-based ultrafiltration membranes.

Ultrafiltration-based polyacrylonitrile membranes (UF-membranes) were evaluated for their ability to retain tissue culture adapted indigenous hepatitis A virus from water. Amicon cell (dead-end ultrafiltration unit)-based experiment was set up and viral assay was carried out using rapid and sensitive reverse transcriptase polymerase chain reaction (RT-PCR). The RT-PCR results show retention of virus particles by the polyacrylonitrile membranes. A protocol for routine virological evaluation of membranes is described and the use of these membranes for water purification units and for virus concentration systems for field application is discussed.

Acrylic Resins↗
PubMed2004

Effect of tissue ultrafiltration on skin flap survival.

OBJECTIVE: Tissue ultrafiltration (TUF) is a method of reducing tissue edema by removal of interstitial fluid. Considering the deleterious effects of edema on microcirculation and tissue viability, the effect of TUF on skin flap survival was tested. STUDY DESIGN AND SETTING: Survival of modified McFarlane skin flaps was determined in 40 Sprague-Dawley rats. In 20 treated animals, four 5-cm ultrafiltration catheters were placed in the subdermal plane of the distal flap 24 hours after flap elevation and connected to a down-regulated vacuum manifold for 8 hours. No catheters were placed in the control group. RESULTS: Skin flap survival was improved in the experimental group (87.2 +/- 1.6) over the control group (76.7 +/- 2.2). DISCUSSION: TUF effectively improved skin flap survival. These results provide evidence of the causal effect of edema on tissue viability. The relative ease of use of TUF would allow cost-effective clinical application of this technique.

Animals↗
PubMed2005

The optimisation of ultrasonic cleaning procedures for dairy fouled ultrafiltration membranes.

Ultrafiltration (UF) of whey is a major membrane based process in the dairy industry. However, commercialization of this application has been limited by membrane fouling, which has a detrimental influence on the permeation rate. There are a number of different chemical and physical cleaning methods currently used for cleaning a fouled membrane. It has been suggested that the cleaning frequency and the severity of such cleaning procedures control the membrane lifetime. The development of an optimal cleaning strategy should therefore have a direct implication on the process economics. Recently, the use of ultrasound has attracted considerable interest as an alternative approach to the conventional methods. In the present study, we have studied the ultrasonic cleaning of polysulfone ultrafiltration membranes fouled with dairy whey solutions. The effects of a number of cleaning process parameters have been examined in the presence of ultrasound and results compared with the conventional operation. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath. Results show that ultrasonic cleaning improves the cleaning efficiency under all experimental conditions. The ultrasonic effect is more significant in the absence of surfactant, but is less influenced by temperature and transmembrane pressure. Our results suggest that the ultrasonic energy acts primarily by increasing the turbulence within the cleaning solution.

Animals↗
PubMed2004

Studies on the effect of humic acids and phenol on adsorption-ultrafiltration process performance.

Application of pressure-driven membrane processes, such as ultrafiltration (UF) and microfiltration (MF) for surface water treatment have become very popular during last decades. Membrane fouling by humic substances (HS) is one of the major limiting factors in these processes. In order to alleviate the unfavorable effects of the presence of HS in the feed on the process performance UF and MF are often combined with adsorption on powdered activated carbon (PAC). The main goal of the present study was to evaluate the effect of humic acid (HA) on membrane fouling during UF. Moreover, the effect of PAC addition to the feed on UF process, especially on flux decline was determined. The applicability of the adsorption-ultrafiltration (PAC/UF) system to purification of water containing low (phenol) and high molecular (HA) was also investigated. Three different polymer UF membranes, prepared from polysulfone (PSF), cellulose acetate (CA) or polyacrylonitrile (PAN) were applied. It was found that the membranes prepared from PSF and CA are very susceptible to fouling caused by HA. The permeate flux decreased for ca. 50% during UF of HA solution through the PSF membrane and for ca. 45%-through the CA membrane. In the case of the PAN membrane, a negligible effect of HA on the flux was observed. On the basis of the FTIR spectra it was found that the drop in the permeate flux through these membranes may result from interactions between the negatively charged functional groups present on the membrane surface, such as carboxyl groups (CA) and sulfone groups (PSF) with HA, which results in coating of the membrane surface with HA. When PAC was added to the feed containing HA, the permeate flux through the CA and PAN membranes was maintained on a practically unchanged level. However, in case of the PSF membrane, a 50% drop in the permeate flux in comparison with the flux value, when process was conducted without PAC addition was observed. That was supposed to be due to attractive forces among hydrophobic PAC particles, HA molecules and PSF membrane surface. The performed studies showed that the application of PAC/UF system was very effective in the removal of organic substances having both, low and high molecular weights. The role of PAC suspended in a feed in the PAC/UF system is the adsorption of low molecular organic compounds, which cannot be removed by UF alone.

Adsorption↗
PubMed2003

Utilization of in vivo ultrafiltration in biomedical research and clinical applications.

Ultrafiltration (UF) is a filtrate selection method with a wide range of biomedical and clinical applications, including detoxification of blood in hemodialysis and peritoneal dialysis. New is, however, the use of UF as a convenient in vivo sampling method that, for example, has been used in diabetics. Ultrafiltration avoids complicated and time-consuming recovery calculations that are necessary when using in vivo microdialysis, as recoveries of low molecular weight molecules are near 100%. The subcutaneously or intravenously placed UF probes have been studied for off-line sample analysis and for continuous on-line monitoring, in a wide variety of species, including dogs, rats, pigs and humans. This review discusses the potential of in vivo UF as a continuous tissue sampling technique in clinical research areas, and in several major biomedical applications including glucose and lactate monitoring and drug kinetic studies.

Animals↗
PubMed1996

Electron microscopic study of possible sites of ultrafiltration in Lumbricus terrestris (Annelida, Oligochaeta).

Electron microscopic investigations of blood vessels of Lumbricus terrestris (L. terrestris) were conducted to show sites of filtration such as podocytes or irregular fenestrations. The endothelia of the blood vessels consist of myoendothelial cells, chloragocytes and podocytes. The podocytes form large archs over a considerable area of the vessels. Numerous small pedicels are presented on the lumen side and the gaps between adjacent pedicels are bridged by slit membranes. The podocytes are restricted to the front part of the ventral vessel. They are regarded as the structural basis for ultrafiltration. Additionally to the filtration site between ventral vessel and coelomic cavity, a second putative filtration site was found in the front part of the body between intestinal blood sinus and coelomic cavity. The endothelium of the sinus is formed by myoendothelial cells, pedicels and chloragocytes with footlike processes. In such areas the basement membrane is the only continous layer between blood vessel and coelomic cavity. The basement membrane of the blood vessels of L. terrestris is a characteristic association of three layers of different composition and thickness. Possible filtration sites in form of podocytes and irregular fenestrations could be localized at the border between the blood compartment and the coelomic compartment. Presumably the primary urine is formed by ultrafiltration of blood.

Animals↗
PubMed2001

Removal of chromium from aqueous solution by complexation-ultrafiltration using a water-soluble macroligand.

A process for purifying waste waters containing heavy and toxic metal such as chromium has been studied. A batch complexation-ultrafiltration process was used to concentrate and recover chromium from sulphate solution. As the chromium ions are too small to be retained by the filter, they are first complexed with a water-soluble macroligand (polyethylene-imine). Factors affecting the rejection rate and permeate flux such as pH, concentration ligand, chloride and sulphate concentration, membrane pore size, applied pressure and extraction factor were investigated. Best operating conditions can be obtained in order to achieve high levels of removal (> 95%). Then, decomplexation is obtained so that metal can be separated from macroligand by a second ultrafiltration plant to reuse the macroligand.

Chlorides↗
PubMed1996

Hemodialysis alternative with ascites ultrafiltration for an end-stage renal failure patient associated with tense ascites secondary to decompensated liver cirrhosis.

Patients with end-stage renal disease combined with tense ascites caused by decompensated liver cirrhosis are sometimes encountered in a hemodialysis center. A big problem for the management of these patients is the tendency of hypotension during ultrafiltration. Subsequent fluid accumulation, especially in the abdominal cavity, causes breathing difficulty and abdominal discomfort. We present a new technique, ascites ultrafiltration, to solve this problem. Using the same equipment as for ordinary hemodialysis, and incurring the same cost, we removed directly approximately 8 L of ascites fluid during each nearly 4-hour session. No hemodynamic instability was noted. We proved this technique to be an effective and safe alternative method for this group of patients.

Ascites↗
PubMed2000

Validation of high-performance liquid chromatographic assay methods for the analysis of carboplatin in plasma ultrafiltrate.

Validation of two HPLC assays for the quantitation of carboplatin in human plasma ultrafiltrate is described. Both assay methods employed a YMC ODS-AQ 3.9 x 150 mm (3 microm) column for the chromatographic separation. The first method utilized direct UV detection, the second method utilized UV detection following post-column derivatization with sodium bisulfite. Structural analogues of carboplatin were synthesized and used as internal standards for the assays. With direct UV detection, sample clean-up using solid-phase extraction on amino cartridges was required prior to injection, with extraction recoveries ranging from 80 to 90%. This extraction procedure was not necessary with the post-column reaction method, which employed a more selective analytical wavelength. Unfortunately, instability of the post-column reagent was a problem and led to greater variability in predicted concentration values. For standard curves, a weighted (1/y2) regression approach was used for plots of peak area or peak height ratio (carboplatin/internal standard) vs. carboplatin concentration. The limit of detection of both assays was 0.025 microg/ml and both were validated for carboplatin concentrations from 0.05 to 40 microg/ml. Accuracy and precision data were generated using three batches of validation samples, each batch consisting of a standard curve and five sets of quality control samples. Stability of carboplatin in blood, plasma, plasma ultrafiltrate, and reconstituted extracts was evaluated. The assay methods were employed for the pharmacokinetic analysis of blood samples drawn from a pediatric patient that received a 400 mg/m2 dose of carboplatin.

Antineoplastic Agents↗
PubMed2001

Ultrafiltration to fractionate wheat polypeptides.

An ultrafiltration process allowing the fractionation of two kinds of polypeptides issued from limited chymotryptic hydrolysis of wheat gliadins was applied to wheat gluten hydrolysates. Hydrophilic and poorly charged polypeptides were well transmitted through an inorganic ZrO2-based membrane at acidic pH, whereas hydrophobic and positively charged polypeptides were highly retained. By combining reversed-phase and cation-exchange chromatography (CEC), it was proved that the fractionation of the polypeptides was based on electrostatic repulsion of the charged polypeptides by the positively charged membrane. After a continuous diafiltration process, retentates containing 75 to 88% of hydrophobic polypeptide and permeates containing 84 to 90% of hydrophilic polypeptides were recovered, depending on the size of membrane used. Even if the ultrafiltration fractions were less purified than fractions issued from CEC, it was shown that they exhibited very different foaming properties: permeate did not produce nor stabilize foams, whereas retentate was more efficient than the whole hydrolysates and BSA.

Chromatography, Gel↗
PubMed2001

Role of electrophoretic mobility of protein on its retention by an ultrafiltration membrane. Comparison to chromatography mechanisms.

Lysozyme and lactoferrin, two globular proteins, were first studied separately in order to elaborate a strategy for the improvement of their separation by ultrafiltration (UF) with zirconia-based membranes of different charge sign and pore radius. The electrophoretic mobility (mu) at fixed pH and variable ionic strength was used for the characterisation of both proteins and zirconia particles, similar to the active layer of the membrane during the UF run. Specific adsorption of phosphate ions was shown for both proteins resulting in new isoelectric points. The occurrence of electrostatic exclusion mechanism in addition to the molecular sieving in UF of charged solutes was shown for: * Low molecular weight solute: multivalent citrate at pH 6 was specifically adsorbed on zirconia and its transmission through the membrane (defined as the ratio of the concentration in the permeate to that of the feed solution) was reduced in the range 0.001-0.01 mol l(-1) of citrate concentration * Proteins: their transmissions increase when the ionic strength increases (ion-exchange is not the relevant mechanism because transmission is irrespective of the initial charge of the membrane compared with the protein charge). A model based on convection, diffusion and electrophoretic migration mechanisms (CDE model) was proposed to take into account this behaviour. The CDE model predicts the possible existence of a depleted sub-layer of the charged protein in the concentration polarisation layer, located in the close vicinity of the membrane surface. A strategy for the separation of two proteins in mixed solution was proposed by varying both the physico-chemical environment in the feed solution (pH, ionic strength, chemical nature of the electrolyte) and the membrane pore radius. Maximum selectivity was obtained when the target protein (to be transmitted in the permeate side) is close to being uncharged due to specific adsorption of electrolyte ions. Ultrafiltration selectivity is enhanced with membrane of large pore radius, which provides high transmission of the target protein and efficient electrostatic exclusion of the solute to be retained in the retentate side. This UF approach corresponds roughly to the separation of one uncharged and one charged protein from a mixed solution by size exclusion chromatography of the uncharged protein combined with electrostatic exclusion of the charged protein due to packing of similar charge.

Chromatography, High Pressure Liquid↗
PubMed2001

Determination of albumin and myoglobin in dialysate and ultrafiltrate samples by high-performance size-exclusion chromatography.

A high-performance size-exclusion chromatographic method was developed, validated and implemented for simultaneous and quantitative determination of albumin and myoglobin along with inulin, vancomycin and creatinine in dialysate and ultrafiltrate samples from in vitro hemodialysis experiments. The experimental parameters including mobile phase pH, ionic strength, detection wavelength, flow-rate, injection volume were first optimized for the determination of albumin, myoglobin, inulin, vancomycin and creatinine. The peak height ratio and detection limits of the proteins were then comparatively studied at 210, 254 and 280 nm by UV and diode array detection. The method was further validated by evaluating the linearity, precision and accuracy of the proteins. The assay was finally implemented to the simultaneous and quantitative determination of the proteins in dialysate and ultrafiltrate samples.

Albumins↗
PubMed1998

Determination of metformin in plasma by high-performance liquid chromatography after ultrafiltration.

A rapid high-performance liquid chromatography (HPLC) method was developed for determination of metformin, an oral antidiabetic agent, in plasma. Sample preparation entailed a 30-min centrifugation of plasma through a micron filter with direct injection of the protein-free ultrafiltrate into an HPLC system consisting of a cation-exchange extraction column (7.5x4.6 mm), a column switching valve, and a cation-exchange analytical column (250x4.6 mm). The eluent was monitored at 232 nm. Metformin was well resolved at a retention time of about 5 min. There was less than 2% loss of metformin during ultrafiltration and good linearity was established from 0.10 to 40 mg/l of metformin hydrochloride. The lower limit of quantitation was about 0.05 mg/l, at which concentration the signal-to-noise was above 10. The intra- and inter-assay coefficients of variation at plasma concentrations of metformin hydrochloride between 0.25 and 25 mg/l were typically 0.8-1.4% and 3.5-6.4%, respectively. This method offers a rapid sample preparation time and achieves excellent sensitivity without resorting to extraction and evaporation techniques.

Anticoagulants↗
PubMed1999

Determination of non-protein bound phenylbutazone in bovine plasma using ultrafiltration and liquid chromatography with ultraviolet detection.

A liquid chromatographic procedure using UV detection was coupled with ultrafiltration for the quantitation of free phenylbutazone in bovine plasma, in the range of 20 ng/ml to 2.0 microg/ml. Whole plasma samples (0.5 to 1 ml) were placed in a 2-ml centrifugal concentrator with a molecular-mass cut-off membrane of 10000 and centrifuged at 4500 g for 2 h at 4 degrees C using a fixed angle rotor. The ultrafiltrate was transferred to an LC vial with a 200-microl insert and 100 microl was injected into an LC system. The chromatographic system used a C18 reversed-phase column connected to a UV detector set at 264 nm. The mobile phase was 0.2 M sodium phosphate buffer (pH 7)-methanol (1:1). Recoveries of phenylbutazone from protein-free plasma water fortified at levels of 20 ng/ml to 2 microg/ml ranged from 91 to 93%, with relative standard deviations (R.S.D.s) ranging from 1 to 4%. The concentration of incurred non-protein bound phenylbutazone obtained from a cow intravenously dosed twice with 2 g phenylbutazone, 8 h apart, was 111, 26 and 11 ng/ml for 2, 72 and 104 h post first phenylbutazone dose, respectively.

Animals↗
PubMed2000

Ultrafiltration of large volumes for the determination of colloidally bound artificial radionuclides in natural waters.

A methodology based on large volume ultrafiltration (> 1000 l) is developed in order to characterize the artificial radionuclides associated with the colloidal populations in natural waters. "Inorganic elements" and organic carbon sinks or sources due to sorption or post desorption within the ultrafiltration assembly/membranes of the Sartorius system are underlined and discussed from methodological step experiments as well as recoveries obtained for artificial radionuclides such as 106Ru, 125Sb, 137Cs and 239+240Pu fractionating natural waters from the Rhône River (France), its estuary and the Mediterranean Sea (Gulf of Lions).

Colloids↗
PubMed2001

Influence of modified ultrafiltration on coagulation, fibrinolysis and blood loss in adult cardiac surgery.

OBJECTIVES: Modified ultrafiltration (MUF) significantly reduce blood loss and transfusion requirements in pediatric cardiac surgery presumably by a reduction in inflammatory mediators which decrease the inflammatory axes and decrease the cross-activation of fibrinolysis and thrombosis. The influence of MUF on blood loss and homologous blood transfusion in adult cardiac surgery has not yet been determined. Furthermore, data about the influence on routine coagulation tests, platelet activation as well as the coagulation and fibrinolytic systems are limited. METHODS: In a prospective randomized study 48 patients scheduled for elective myocardial revascularization were randomized into a control group (n=16), a conventional ultrafiltration (CUF) group (n=16) and a MUF group (n=16). Perioperatively, serial blood samples were drawn at specific intervals to evaluate coagulation, fibrinolysis, and platelet function. RESULTS: Neither the coagulation nor the fibrinolytic system was positively influenced by MUF or CUF. The routine clotting tests were comparable except for a significantly higher antithrombin III activity after MUF compared to the CUF control group persisting 24 h postoperatively. Platelet factor 4 activity and platelet counts showed no differences among the groups. MUF considerably reduced the postoperative blood loss (MUF, 6.4+/-1.7 ml/kg bw per 24 h vs. CUF, 9.2+/-2.5 ml/kg bw per 24 h (P=0.003) vs. control, 8.9+/-2.2 ml/kg bw per 24 h (P=0.008)) and allogeneic blood transfusion (MUF, 2.0+/-3.4 ml/kg bw per 24 h vs. CUF, 6.9+/-5.1 ml/kg bw per 24 h (P=0.034) vs. control, 7.0+/-6.3 ml/kg bw per 24 h (P=0.029)). CONCLUSIONS: MUF in adult cardiac surgery significantly reduces postoperative blood loss and transfusion requirements. The mechanism for reduced blood loss could not be elucidated in this study.

Antithrombin III↗