Apparatuses and methods are disclosed which can be used in the field (i.e., outside the laboratory environment) to determine qualitatively and at least semiquantitatively the presence or absence of minute quantities of ligand. The apparatus can be in the form of a strip comprising a support means provided with a groove intermediate its ends forming a crease line upon which the strip can be folded upon itself with bibulous elements and spaced from the crease line and arranged so that when the strip is folded upon itself the bibulous elements become aligned with each other and come into liquid contact.
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