Fluorinated Ethylene Propylene Copolymer Research Articles

Fluorinated ethylene propylene copolymer coating for the stability enhancement of electroactive and photoactive systems

The effectiveness of radio frequency sputtered fluorinated ethylene propylene copolymer (FEP) for the stability enhancement of electroactive and photoactive systems was investigated. Two kinds of electroactive polymer systems, polyaniline (PANI) coated low density polyethylene (LDPE) film and PANI-viologen assembly, were tested. In both cases, a sputtered FEP coating of <10 nm in thickness significantly enhanced the electrical stability of the films in water. The enhancement of the electrical stability of the PANI-LDPE film was also achieved in basic aqueous solution of pH up to 12 with a FEP coating of 40–50 nm in thickness. The deposition of a FEP coating on the photoactive viologen system (viologen grafted on LDPE film) prolonged its photochromic effect by inhibiting the diffusion of oxygen, and hence the reoxidation of the highly colored viologen radical cations to the dication state.

Proton exchange membranes by grafting of styrene–acrylic acid onto FEP by preirradiation technique. I. Effect of synthesis conditions

AbstractGrafting of styrene–acrylic acid (sty–AA) polymer onto fluorinated ethylene propylene copolymer (FEP) was carried out by preirradiation of FEP with γ‐rays. Effect of reaction conditions on the degree of grafting such as total radiation dose, monomer concentration, temperature, and time of grafting has been studied. From the study, it is seen that the degree of grafting is strongly dependent on the reaction conditions. The rate dependence of 0.53 (∼0.5) and 1.03 (∼1) have been obtained with respect to total dose and monomer concentration, respectively indicating that radiation induced grafting follows free radical polymerization. The activation energy for the grafting in the temperature range of 60–90°C is found to be 33 kJ/mol. The results indicate that the grafting takes place by the front mechanism where the grafting starts at surface and slowly proceeds inwards by diffusion of the monomer through the swollen grafted chains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2572–2577, 2003

Reduced oxygen release from erythrocytes by the acceleration-induced flow shift, observed in an oxygen-permeable narrow tube

The oxygen release from flowing erythrocytes under accelerational force (0–4 g) was examined using an oxygen-permeable, fluorinated ethylenepropylene copolymer tube (25 μm in inner diameter). The narrow tube was fixed vertically on the rotating disk of a new centrifuge apparatus, and erythrocyte suspension was perfused in the direction of Earth gravity. The accelerational force was applied perpendicularly to the flow direction of cells by centrifugation. The microscopic images of the flowing cells obtained at five different wavelengths were analyzed, and marginal cell-free layer and oxygen saturation of the cells were measured. By lowering oxygen tension around the narrow tube, erythrocytes were deoxygenated in proportion to their traveling distance, and the deoxygenation was enhanced with decreasing flow velocity and hematocrit. With increase of the g-value, the shift of flowing erythrocyte column to the centrifugal side was increased, the column was compressed, and the oxygen release from the cells was suppressed. Qualitatively, similar results were obtained by inducing erythrocyte aggregation with Dextran T-70 (MW=70,400), without accelerational force. These results conclude that both the accumulation of erythrocytes under accelerational force and the enhancement of erythrocyte aggregation by macromolecules lead to the reduction of oxygen release from the flowing cells.

PEO-like plasma polymerized tetraglyme surface interactions with leukocytes and proteins: in vitro and in vivo studies

Polyethylene oxide (PEO) surfaces reduce non-specific protein and cell interactions with implanted biomaterials and may improve their biocompatibility. PEO-like polymerized tetraglyme surfaces were made by glow discharge plasma deposition onto fluorinated ethylene propylene copolymer (FEP) substrates and were shown to adsorb less than 10 ng/cm2 of fibrinogen in vitro. The ability of the polymerized tetraglyme surfaces to resist leukocyte adhesion was studied in vitro and in vivo. Polymerized tetraglyme and FEP were implanted subcutaneously in mice and removed after 1 day or 4 weeks. Histological analysis showed a similar degree of fibrous encapsulation around all of the 4-week implants. Darkly stained wells were present in the fibrous tissues at the tissue-material interface of both FEP and tetraglyme. Scanning electron micrographs showed that in vivo macrophage adhesion to polymerized tetraglyme was much higher than to FEP. After 2-hour contact with heparinized whole blood, polymorphonuclear leukocyte (PMN) adhesion to polymerized tetraglyme was much higher than to FEP, while platelet adhesion to polymerized tetraglyme was lower than to FEP. When PMNs isolated from blood were suspended in 10% autologous plasma, cell adhesion to polymerized tetraglyme was higher than to FEP; however when the cells were suspended in heat inactivated serum, cell adhesion to FEP was higher than to polymerized tetraglyme. The surface chemistry of polymerized tetraglyme did not change after 2-hour blood contact, but displayed nitrogen functional groups after 1-day implantation and became slightly degraded after 4-week implantation. The surface chemistry of FEP did not change significantly after blood contact or implantation. Loosely bound proteins such as fibrinogen on polymerized tetraglyme may contribute to the adhesion of PMNs and macrophages and ultimately to fibrous encapsulation (the foreign body response) around the implants.

O(2) release from erythrocytes flowing in a narrow O(2)-permeable tube: effects of erythrocyte aggregation.

The effects of erythrocyte aggregation on O(2) release were examined using O(2)-permeable fluorinated ethylenepropylene copolymer tubes (inner diameter, 25 microm; outer diameter, 100 microm). Measurements were performed using an apparatus built on an inverted microscope that contained a scanning-grating spectrophotometer with a photon count detector connected to two photomultipliers and an image processor through a video camera. The rate of O(2) release from the cells flowing in the narrow tube was determined based on the visible absorption spectrum and the flow velocity of the cells as well as the tube size. When the tube was exposed to nitrogen-saturated deoxygenated saline containing 10 mM sodium dithionite, the flowing erythrocytes were deoxygenated in proportion to the traveling distance, and the deoxygenation at a given distance increased with decreasing flow velocity and cell concentration (hematocrit). Adding Dextran T-70 to the cell suspension increased erythrocyte aggregation in the tube, which resulted in suppressed cell deoxygenation and increased marginal cell-free-layer thickness. The deoxygenation was inversely proportional to the cell-free-layer thickness. The relation was not essentially altered even when the medium viscosity was adjusted with Dextran T-40 to remain constant. The rate of O(2) release from erythrocytes in the tube was discussed in relation to the O(2) diffusion process. We conclude that the diffusion of O(2) from erythrocytes flowing in narrow tubes is inhibited primarily by erythrocyte aggregation itself and partly by thickening of the cell-free layer.

Surface immobilization of poly(ethylene oxide): Structure and properties

We covalently immobilized poly(ethylene oxide) (PEO) chains onto a fluorinated ethylene propylene copolymer (FEP) surface. On the FEP surface, aldehyde groups were first deposited by plasma polymerization of acetaldehyde or acrolein. Then, amino-PEO chains were immobilized through Schiff base formation, which was followed by reduction stabilization with sodium cyanoborohydride. The PEO-grafted polymer surfaces thus prepared were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, contact-angle measurements, and protein adsorption. The dramatic increase in the CO intensity of the high-resolution XPS C 1s spectrum, together with an overall increase in oxygen content, indicated the successful attachment of PEO chains onto the acetaldehyde plasma surfaces. The amount of grafted PEO chains depended on the superfacial density of the plasma-generated aldehyde groups. The grafted monoamino-PEO chains formed a brushlike structure on the polymer surface, whereas the bisamino-PEO chains predominately adopted a looplike conformation. The PEO surface had a regular morphology with greater roughness than the aldehyde surface underneath. Surface hydrophilicity increased with the grafting of PEO. Also, the bisamino-PEO-grafted surface had slightly higher surface hydrophilicity than its monoamino-PEO counterpart. These PEO coatings reduced fibrinogen adsorption by 43% compared with the substrate FEP surface. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2323–2332, 2000

A study of a simulated low Earth environment on the degradation of FEP polymer

Spacecraft flying in a low Earth orbit environment require thermal blankets to provide protection from direct solar heat from the sun. Fluorinated ethylene propylene copolymer is one of the major components of these thermal blankets. In this study, the effect of a simulated low Earth orbit environment on FEP was investigated. UV and VUV degradation of fluorinated ethylene propylene (FEP) copolymer was studied using ESR and XPS. The ESR study revealed the formation of a terminal polymer chain radical. The stability of this radical has been investigated under different environments. An XPS study of FEP film exposed to VUV and atomic oxygen showed that oxidation takes place on the polymer surface. The study revealed also that the percentage of CF in the polymer surface decreased with exposure time and the percentage of CF, CF and carbon attached to oxygen increased. SEM micrographs of FEP film exposed to VUV and atomic oxygen produced a rough surface with regular undulations similar to sand dunes.

Capillary zone electrophoresis in a hydrodynamically closed separation system with enhanced sample loadability

Some phenomena linked with capillary zone electrophoresis (CZE) performed in a hydrodynamically closed separation system with enhanced sample load capacity via the use of capillary tubes of larger I.D.s were studied. Calculations of the plate heights for varying amounts of the analytes loaded onto 50 and 300 μm I.D. columns under identical CZE separating conditions revealed that the analytical advantages of using columns of larger I.D. include significantly reduced contributions of electromigration dispersion. At higher concentrations of the carrier electrolytes this gain, however, can be partially lost due to increased thermal dispersive effects. Calculated resolutions for a varying ratio of a pair of the analytes loaded onto 50 and 300 μm I.D. columns favoured the use of the latter I.D. in situations when the ratio of the analytes was higher than ca. 102:1. CZE experiments were carried out in a 300 μm I.D. capillary tube made of fluorinated ethylene–propylene copolymer (FEP) with a porous cellophane membrane serving as a hydrodynamic barrier to prevent a flow of the solution in the separation compartment due to a pressure difference between the electrode vessels. Movement of the membrane was found to be a source of undesired flows in the separation compartment, which adversely affected both the reproducibilities of migration times of the analytes and their separation efficiencies. Mechanical support eliminated these problems. Dispersive phenomena associated with electroosmosis in the closed separation compartment were effectively suppressed by using high molecular weight derivatives of water soluble polymers (methylhydroxyethylcellulose and polyethyleneglycol) in the carrier electrolyte solutions. Examples from the separations of various groups of analytes (synthetic food colourants, some inorganic anions, alkali and alkaline earth metal cations and glycoforms of erythropoietin) are given to illustrate a practical utility of the studied CZE approach.

Determination of nitrophenols by capillary zone electrophoresis in a hydrodynamically closed separation compartment

The use of β-cyclodextrin (β-CD) and polyvinylpyrrolidone (PVP) as complexing agents to capillary zone electrophoretic (CZE) separations of a group of ten nitrophenols was investigated. The analytes were baseline resolved in one CZE run when PVP was present in the carrier electrolyte at a 2.5% (w/v) concentration. β-CD was less effective as it did not baseline resolve a complete group of the studied nitrophenols within an applicable concentration range (0–10 mmol/l). The separations were carried out in a 300-μm I.D. capillary tube made of fluorinated ethylene–propylene copolymer to enhance the load capacity of the separation system. Under these working conditions, a 100-nl sample injection volume resulted in 20–80 ppb concentration limits of detection for nitrophenols, using a photometric absorbance detector operating at a wavelength of 254 nm. The separation efficiencies for the analytes spanned from 1.6–2·105 theoretical plates per meter. Their migration times were reproducible not only in a within day but also in a day-to-day time frame (1% or less for a period of several weeks). This was achieved for a hydrodynamically closed separation compartment while minimizing fluctuations in the concentration of CO2 in the carrier electrolyte. Reproducibility in the determination of nitrophenols was in the range of 1–5% for 1–6 ppm concentrations. Rain, drinking and process water samples served as matrices to assess the practical applicability of the elaborated CZE procedure. This procedure can be combined with isotachophoretic sample pretreatment to make its use possible in situations when nitrophenols are present in the samples at low ppb concentrations.

A direct current piezoelectric effect in fluorinated ethylene-propylene copolymer due to space charge

A dc piezoelectric effect was observed in corona charged fluorinated ethylene-propylene membranes. After an appropriate thermal treatment the charge deposited on the sample surface penetrated the bulk material, with the charge centroid remaining at the center of the sample was indicated by heat pulse measurements. The charged sample responded to an applied pressure with a constant voltage signal or, if in short circuit, with a transient external electric current. This phenomenon was interpreted as being caused by a relative movement of the stored charges with respect to the material structure. A semiquantitative analysis based on this relative movement was carried out that allowed physical parameters such as the volumetric charge density and the longitudinal piezoelectric coefficient to be obtained.

The behaviour of red cells in narrow tubes in vitro as a model of the microcirculation.

To investigate the behaviour of red cells in the microcirculation, we established a new capillary method using narrow fluorinated ethylenepropylene copolymer tubes with internal diameters of 12.5 and 25.0 microns. Red cell flow in the tubes under a given range of pressure was analysed through a video system connected to a microscope. The experimental condition was adjusted so that the velocity of the control normocytes would be compatible with that in corresponding vessels in vivo, 0.5-1.5 mm/s. In the 12.5 microns tube, normocytes obtained from 12 young normal volunteers ran in an axisymmetric edge-on orientation with a folded shape at higher pressures, but rolled along freely without deformation at lower pressures. Deformation during the passage of the microcytes obtained from four patients with polycythaemia vera complicated with iron-deficient microcytosis and 10 patients with iron deficiency anaemia was relatively mild, whereas that of the macrocytes obtained from eight patients with refractory anaemia was marked. Even after the screening effect at the tube entrance was taken into consideration, the velocities of both microcytes and macrocytes were found to be significantly lower than the control normocytes. Therefore this method may be a new way to investigate the flow properties of red cells in the microcirculation.

Separation of synthetic food colourants by capillary zone electrophoresis in a hydrodynamically closed separation compartment

Separation conditions enabling the complete resolution of eleven permitted synthetic food colourants and some of their subspecies by capillary zone electrophoresis (CZE) were determined. Those conditions involve combining a suitable pH of the carrier electrolyte (pH 6.8) with host-guest complexation effects of β-cyclodextrin. A 300 μm I.D. capillary tube made of fluorinated ethylene-propylene copolymer in a hydrodynamically closed separation compartment was used for the CZE separations. The capillary could accommodate 90-nl sample injection volumes, thus providing limits of detection for the dyes of 11–300 ppb using a photometric detector operating at a wavelength of 254 nm. R.S.D.s of 0.4–3.0% were typical for the determinations of the dyes present in samples at 16 ppm concentrations. Erythrosine, exhibiting residual adsorption, gave more-scattered results under identical working conditions (R.S.D. of ca. 9.0%). The utility of this rapid CZE procedure (migration times of the dyes were 2.5–10.5 min) is illustrated for several practical samples, including soft drink concentrate and liqueur and monitoring of the stability of aqueous solutions of indigo carmine.

Capillary zone electrophoresis of inorganic anions with conductivity detection.

A carrier electrolyte system for capillary zone electrophoresis (CZE) resolving chloride, bromide, iodide, fluoride, nitrite, nitrate, sulfate, and phosphate in a hydrodynamically closed separation compartment is described. The carrier electrolyte combines the effects of pH, polyvinylpyrrolidone (PVP) and the counterionic constituent on the effective mobilities of the anions. In 300 microns ID capillary tubes made of fluorinated ethylene-propylene copolymer (FEP), and with detection of analytes with the aid of an alternating current conductivity detector, detection limits in the range of 3-10 ppb could be achieved for 200 nL sample volumes. The separation efficiencies were in the range of 1.5-2.5 x 10(5) theoretical plates per meter for an adequate sample load. The reproducibility was evaluated for two concentration levels. For concentrations close to the limits of quantitation (50-120 ppb), the RSD values ranged from 1.5-12.6%, with the highest scatter for fluoride and phosphate. The RSD values were in the range of 0.4-1.5% for 300-1200 ppb concentrations of the anions. Typical analysis times were 2-5 min, depending on the anion species. A series of water samples (drinking, river, rain) was used to assess the practical applicability of the CZE method. The method is a suitable alternative for the determination of both anionic macro- and microconstituents in water with a good overall selectivity.

Surface stress‐dependent adhesion to fluorinated polymers

AbstractIrradiation of thin commercial sheets of poly(tetrafluoroethylene) (PTFE) or a fluorinated ethylene‐propylene copolymer (FEP) yield essentially the same results with mass spectroscopy or x‐ray photoelectron spectroscopy (XPS). For both gas phase and surface (ca. 30 Å) products of irradiation, the same product distributions and exposure dependencies are observed. In addition, XPS of chemically etched (with sodium naphthalenide) PTFE and FEP shows the same extent of surface defluorination. In contrast to the more surface‐sensitive XPS, Rutherford backscattering spectroscopy of etched PTFE shows that the defluorination extends to depths of ca. 3000 Å, while with etched FEP defluorination extends to only a few hundred Angstroms. Scanning electron microscopy shows the FEP surface to be smooth and featureless both before and after chemical etching, while etched PTFE is characterized by a crazed surface with a high density of unidirectional cracks oriented perpendicular to long macroscopic scratches existing in the virgin surface. Adhesion of Cu to this etched PTFE has previously been shown to be sufficiently strong that failure is a result of near‐cohesive failure in the PTFE and not adhesive failure. Conversely, weak adhesion of Cu to etched FEP or to other smooth forms of fluorinated polymers, including polished PTFE, is observed. This correlation of strong adhesion with surface roughness and not with surface chemical changes is consistent with previous suggestions that a major component of adhesion to fluorinated polymers is mechanical interlocking. The differences between FEP and PTFE are discussed in terms of a model involving surface stresses expected from their different methods of manufacture: extrusion from the melt in the case of FEP and skiving from pressed cylinders in the case of PTFE. © 1994 John Wiley &amp; Sons, Inc.

Correlation between corneal epithelial cell outgrowth and monoclonal antibody binding to the cell binding domain of adsorbed fibronectin.

The ability of corneal epithelial cells to attach, spread, and migrate on synthetic surfaces is largely determined by the characteristics of the adsorbed protein layer. In previous studies we have described an in vitro model for quantitating epithelial cell outgrowth from explanted corneal buttons onto synthetic materials (Pettit et al., Invest. Ophthalmol. Vis. Sci., 31, 2269 [1990]). We have also described the role of fibronectin (fn) adsorption and binding strength on epithelial cell outgrowth (Pettit et al., J. Biomed. Mater. Res., 26, 1259 [1992]). In the current study we have used a monoclonal antibody against the RGD cell binding domain of fn (mAb 3E3) to further characterize the role of adsorbed fn in promoting epithelial cell outgrowth. Ten materials of diverse chemical and physical properties were adsorbed with fn (0.1 mg/ml) or mixtures of fn and albumin (concentrations totaling 0.1 mg/ml) and tested for antibody recognition of the cell binding domain. The surface density of bound anti-cell binding domain antibody varied from a low of 0.66 +/- 0.11 for fluorinated ethylene propylene copolymer (FEP) to a high of 1.90 +/- 0.26 for tissue culture polystyrene dish substrates (units are OD at 450 nm measured in the ELISA technique normalized to polyethylene). A general increase in cell outgrowth areas was noted, with increases in recognizable cell binding domain. However, several exceptions to this trend were noted as well (e.g., low cell outgrowth but high antibody recognizability for glass). These results suggest that, although the number of cell binding domains exposed on adsorbed fn molecules may influence cell outgrowth, other characteristics of the adsorbed protein, such as the binding strength to the underlying substrate, may be equally important in characterizing epithelial cell-substrate interactions.

Patterned neuronal attachment and outgrowth on surface modified, electrically charged fluoropolymer substrates.

Fluorinated ethylenepropylene copolymer (FEP) and polyvinylidene fluoride (PVDF) can generate static and transient electrical charges, respectively, after bulk molecular rearrangements induced by electrical charging techniques. Neurons cultured on electrically active FEP and PVDF show increased levels of nerve fiber outgrowth compared to electrically neutral material. The purpose of the present study was to determine if the addition of charged surface groups to the surfaces of FEP and PVDF would modify the influence of bulk electrical charges on cultured neurons. Mouse neuroblastoma (Nb2a) cells were cultured on electrically charged and uncharged FEP and PVDF substrates with covalently modified surfaces containing hydroxyl (OH) and amine (NH2) groups. Surface chemical modification was performed on the entire surface or in discrete striped regions. Nb2a cells cultured on electrically active FEP and PVDF showed greater levels of differentiation than cells on electrically neutral substrates. The presence of NH2 groups attenuated these responses in serum-containing media. Cells attached to NH2 rich surfaces generally displayed a flatter morphology and tended to remain attached for longer time periods. Cells cultured on stripe-modified substrates in serum-containing media showed a strong preferential attachment to modified regions, especially on NH2 stripes. In summary, bulk electrical charges are more important than surface charges in stimulating Nb2a cell differentiation. Surface groups serve to modulate neuronal morphology and confer specific attachment promoting properties in serum-containing media. The development of an optimal neuronal regeneration template may require the incorporation of specific bulk and surface properties.

Broad line NMR studies on radiation effects on polymers

Our previous studies on the radiation effect on polymers made by using the broad line (BL) NMR technique are autoreviewed with emphasis on the usefulness of this technique. The BL NMR was widely applied, before the prevalence of the modern pulse NMR technique, to study the change of molecular motion caused by either the crosslink or the main-chain scission in solid polymers, since both line-shape and line-width of the BL NMR are sensitive to the molecular motion. Low- and high-density polyethylenes grafted with butadiene by γ-rays were examined before and after the crosslinking induced by heat-treatment with dicumyl peroxide. The crosslinking was found to occur between grafted polybutadiene branches. Polytetrafluoroethylene irradiated with neutron-beam was examined before and after heat-treatment. The results show that heat-treatment causes the formation of paracrystals of radiation-scissored polymer chains and hinders the molecular motion. Response of fluorinated ethylenepropylene copolymer to the neutron-irradiation was quite different: a small fluoropropylene fraction inhibited the paracrystal formation.

Effect of fluorinated ethylene propylene copolymer on the wear behaviour of polytetrafluoroethylene

The wear behaviour of polytetrafluoroethylene (PTFE) composites containing various fluorinated ethylene propylene copolymer (FEP) contents rubbing against an AA-7075 aluminium alloy has been evaluated. Wear tests were carried out on a modified pin-on-disc type wear machine under constant sliding conditions: applied stress, 1.87 MPa; sliding speed, 1.3 m s −1. The wear resistances of the PTFE composites were higher than for pure PTFE within the range of all the experimental FEP contents (5–40 wt.%). It is also shown that the PTFE composite with minimum wear rate contains about 35 wt.% FEP. In order to investigate the wear-reducing mechanism, microhardness tests, differential scanning calorimetry (DSC) and micrography have been carried out. The Vickers hardness showed little variation with FEP content. From the DSC results, the FEP peak was observed in the PTFE composites, but not in the wear debris. The molecular weight and crystallinity of PTFE contained in PTFE composites did not change with FEP content; however, those of the wear debris did change. The wear-reducing mechanism of PTFE composites containing various FEP contents is discussed in terms of the load-supporting action of FEP and the changes in the polymer film which are transferred onto the metal counterface.

Comparison of corrosion fatigue cracking of AlLi alloy AA 2090-T8E41 and alloy AA 7075-T651 in salt water : Pao, P.S., Imam, M.A., Cooley, L.A. and Yoder, G.R.Corrosion July 1989 45, (7), 530–535

The wear behaviour of polytetrafluoroethylene (PTFE) composites containing various fluorinated ethylene propylene copolymer (FEP) contents rubbing against an AA-7075 aluminium alloy has been evaluated. Wear tests were carried out on a modified pin-on-disc type wear machine under constant sliding conditions: applied stress, 1.87 MPa; sliding speed, 1.3 m s−1. The wear resistances of the PTFE composites were higher than for pure PTFE within the range of all the experimental FEP contents (5–40 wt.%). It is also shown that the PTFE composite with minimum wear rate contains about 35 wt.% FEP. In order to investigate the wear-reducing mechanism, microhardness tests, differential scanning calorimetry (DSC) and micrography have been carried out. The Vickers hardness showed little variation with FEP content. From the DSC results, the FEP peak was observed in the PTFE composites, but not in the wear debris. The molecular weight and crystallinity of PTFE contained in PTFE composites did not change with FEP content; however, those of the wear debris did change. The wear-reducing mechanism of PTFE composites containing various FEP contents is discussed in terms of the load-supporting action of FEP and the changes in the polymer film which are transferred onto the metal counterface.

Oxygen Transfer Through Flexible Tubing and Its Effects on Ground Water Sampling Results

AbstractA model for the diffusion of gases through polymeric tubing was derived which predicts that the amount of gas transferred is proportional to the tubing length and inversely proportional to the pumping rate. The model was experimentally tested and confirmed for oxygen transfer through fluorinated ethylene‐propylene copolymer (FEP) tubing using tubing lengths and flow rates typical of ground water sampling. Diffusion can introduce measurable concentrations of oxygen into initially anoxic water. Diffusive loss of carbon dioxide from water that is oversaturated with respect to atmospheric CO2 does not measurably affect pH under similar usage conditions.