When a test is developed, the signals at the test and control lines should have a uniform intensity across the width of the strip (2,10,11). This requires that the liquid flow evenly through the membrane and that the detector particles be evenly distributed across the strip. Achievement of these goals is a function of liquid flow through the sample and conjugate pads and the consistency with which the sample is transferred onto the membrane. This is in turn related to the consistency of the materials used for the pads and the uniformity with which they are assembled into finished test strips. Uneven detector particle distribution causes uneven color development at the test and control lines. It is important to recognize that the membrane cannot correct flow and distribution problems arising in the pads.
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