A fluid processing device and methods are provided that can process one or many different fluid samples, detection for each of which can be multiplexed to detect the presence or absence of each of a panel of target sequences, for example 20 different target sequences. The device can comprise a substrate and one or more fluid processing pathways at least partially defined by the substrate. Each fluid processing pathway can comprise a pre-amplification region and two or more amplification regions disposed downstream from and in fluid communication with the pre-amplification region. A burstable valve can be disposed along each fluid processing pathway and the downstream regions can contain pre-loaded ammonia gas to draw an amplified sample downstream.