Hydrophobic polyethylene

Abel et al. (1984) succeeded in expanding the linear range of a glucose electrode up to 40 mmol/1 by covering the enzyme membrane with a perforated hydrophobic polyethylene membrane. As applied subcutaneously and with a p02 of 2-5 kPa the sensor was stable for some hours (Fig. 134). 

The polyethylene membrane covered an electrochemical enzymatic biosensor. The construction scheme of the sensor is displayed in Fig. 25. The electrochemical basic electrodes consist of a platinum anode and a silver-silver chloride cathode. A thermally sensitive layer of glucose oxidase was localized directly on the anode surface and was covered by a 30-pm-thick hydrophobic polyethylene membrane. The biosensor for the detection of the glucose concentration is based on an enzyme (glucose oxidase)-cat-alyzed reaction of the analyte (glucose) and the subsequent electrochemical detection of a reaction product (electron current). A stoichiometric surplus of the coreactant oxygen has to be guaranteed. This is realized by the polyethylene membrane (membrane with analyte door ) controlling the glu-... 

However, in spite of these similarities, the adsorbed amounts and the structure of the adsorbed mucin and collagen layers on the surfaces studied are entirely different. The behavior of these proteins is analyzed here on the hydrophobic polyethylene surface (water contact angle 0 20 95°), on the surface modified polyethy-lenes oxidized polyethylene (0h q 74°) and poly(maleic acid) grafted polyethylene ( Ho0 74°) a d on the hydrophilic mica surface ( H2 0 0°) Acidic pH = 2.75 (for collagen) and slightly alkaline pH = 7.2 (for mucin) were chosen in order to minimize the association of these proteins in solution and to make possible the analysis of their adsorbabilities in comparable conditions. 

Stainless steel bed supports are used extensively in standard and engineered chromatography columns. In contrast with hydrophobic polyethylene sinters, they are easily wetted . The multilayer woven mesh construction offers high porosity and mechanical strength, and may in many cases be cleaned of media particles or by ultrasonic means. However, all stainless steel products are susceptible to corrosion when in prolonged contact with chloride-containing solutions and especially at low pH. 

In 1972, Griffin [66] described the use of starch as particulate filler for low density polyethylene (LDPE) with the aim of giving a paper-like texture and appearance to extrusion-blown LDPE films. The necessity for highly dried starch to avoid defects caused by water volatilization was a financial limitation to the process since it required appropriate storage of the dried starch prior to its use. Another problem was the poor adhesion of the hydrophilic starch granules to the highly hydrophobic polyethylene, which was improved by treating starch with reactive silanes, but this added an extra cost to the process. 

Pronounced minima of interfacial tension at pH = 3 (Fig. 6) may reflect the isomerization reaction of albumin and the presence of a Fast isomeric form (F). It can be seen (Fig. 6), in agreement with other authors 16,38 that N-F transition is sensitive to the salt concentration in the bulk solution. Once again similar influence of the apolar air phase, in our case, and of a hydrophobic polyethylene on albumin adsorption at this pH is demonstrated. 

If an ordinary polyethylene membrane is used instead of PTFE to graft poly(vinyl pyridine) and to quatemarize it, the response time is too slow to be useful. Unlike for the PTFE, the reaction proceeded homogeneously, and hydrophobic polyethylene and hydrophilic quatemarized vinyl pyridine are well mixed. Consequently, the diffusion of water is slow. 

---