Why are the QuantiTect and QuantiFast Multiplex PCR Kits limited to triplex real-time PCR on some cyclers?
FAQ ID -715

The presence of ROX as passive reference dye in the Master Mix of the QuantiTect Multiplex PCR Kit and the QuantiFast Mutliplex PCR Kit limits the use of these kits to triplex PCR on 4-channel real-time cyclers. This is because the ROX dye occupies the channel for detecting probes labeled with ROX, Texas Red, or other equivalent dyes.

However, 4-plex PCR is possible on on instruments equipped with at least 5 channels. Alternatively, if you have a 4-channel real-time cycler that does not use ROX passive reference dye (e.g., iCycler iQ, Rotor-Gene 3000, Mx4000, Mx3000P, Smart Cycler II, LightCycler 2.0), you can use the QuantiTect Multiplex PCR NoROX Kit or the QuantiFast Multiplex PCR +R Kit to perform 4-plex PCR.

Please see table “Real-Time, Multiplex PCR on a Wide Range of Real-Time Cyclers” for compabilities of the QuantiTect Multiplex kits with different real-time cyclers.