Nowadays, a rapid test for detection and control of drugs has been developed by immuno-chromatography methods. Lateral flow assay is one of the common methods.

The LFA detection kit is divided into two categories:

• Sandwich assay
• Competitive assay

The rapid drug detection kit operates in a competitive assay.

In order to make this kind of kit on its release pads, gold nanoparticles are attached to the antibody of drug detection. This antibody is for limited concentration. By applying the analyte containing the drug onto the sample pad and passing it on the release pad, the nanoparticles attached to the antibody are attached to the sample drug. Some drugs are placed on the test line and antibody is placed on the control line. With the arrival of nanoparticles attached to the antibody to this line, its color will be light and consequently the test will be correct. The structure of the competitive detection type kit is as follows: