How long can the Master Mix tubes containing the sample sit before being placed in the reader?

The tubes should be run immediately. This is why the reader should be turned on ahead of time and allowed to come to temperature. The run should be labeled before you set up your tubes. This way, you can carry the tubes directly to the reader, place the tubes in the wells and select Run. It is a good time to check again for air bubbles in the bottom of each tube and making sure each cap is completely pushed down on each tube. WHEN CARRYING THE TUBES TO THE READER, AVOID TOUCHING THE AREA OF TUBES CONTAING THE LIQUID , AS THE HEAT FROM YOUR FINGERS CAN affect the test performance.