Graphite-benzalkonium surface

Autoradiographs of GBH surfaces sometimes show a "strike where the aqueous solution of heparin was delivered by a pipette, and ran down the film, as seen in Figure 1, which shows the two sides of an adsorption sack with graphite-benzalkonium surface. The match of the adsorption pattern on the two surfaces indicates that it was a matter of initial contact with solution, not a property of the surfaces. This pattern was produced on an initially dry GB surface. The solution was 90% cold heparin, 10% tagged heparin, at 67 fig. tagged heparin/ml. The average heparin adsorption, calculated as total (10X radioactive heparin adsorption) from depletion of the solution, was 2.7 fig./cm.2 Sack was rotated 20 hours, with a bubble, at 37 °C. 

Figure 1. Autoradiographs showing uneven adsorption of heparin on an initially dry graphite-benzalkonium surface. A and B are the two sides of a flat adsorption sack. Flow from the point of initial contact of the solution is indicated with an initial strike which did not level in 20 hours rotation, with a bubble, at 37°C. Average heparin adsorption 2.7 pjg./cm2...

Figure 2. Autoradiographs showing uneven adsorption on an initially wet graphite-benzalkonium surface. A and B are two sides of a flat adsorption sack, 10 ml. heparin solution introduced into 5 ml. water, avoiding contact with the walls. Sack rotated 48 hours with bubble at 37°C. initial heparin concentration 638 fig./ml. in 15 ml. average heparin adsorption 4.0 fig./cm.2 autoradiograph exposure 72 hours...

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