Described herein are apparatus and methods for detecting substances of abuse or other analytes in liquids. For example, the apparatus and methods described herein can be used for real-time detection of analytes, such as substances of abuse. The methods comprise providing a detection area comprising a chromatographic membrane capable of receiving the liquid and allowing for migration of the liquid, the chromatographic membrane comprising an anti-analyte antibody-particle conjugate, an analyte-conjugate protein at a test line; exposing at least the first location of the apparatus to the liquid; and determining whether an interaction between the analyte-conjugate protein and the liquid occurs to detect the presence of the analyte. The chromatographic membrane may further comprise an anti-species antibody at a control line. Specific buffers are disclosed, and these buffers may be used in the preparation of the apparatus to overcome challenges associated with miniaturization and challenges associated with exposure
