The capillary flow time of the membrane affects the appearance of the lines by its impact on the rate with which the liquid spreads when the capture reagent solution is dispensed onto the membrane (10). When the liquid stream contacts the membrane, it moves both into the depth of the membrane and laterally. As the flow time of the membrane decreases (i.e., flow rate increases), the lateral spread of the liquid increases. Depending on the rate with which the capture reagent adsorbs to the nitrocellulose, this can cause the applied reagent to also spread into a wider line. To overcome this problem, the reagent can be dispensed at a higher concentration in a lower volume to apply the same mass. If adsorption occurs at the point of the dispensing, the buffer may actually spread farther than the capture reagent.
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