$Q$ factor refers to what on a lowpass filter? (EE kind of definition)
For lowpass and highpass filters, Q factor is not well defined. What is defined is the cutoff frequency and bandwidth. 

Q factor is useful for bandpass or bandstop (notch) filters as it shows the selectivity of the BPS. Quantitatively Qf is the ratio of the center frequency of the pass-band to the bandwidth of the pass-band. Assuming the system has only a single pass band.

For a highpass filter, since the bandwidth is infinite, this Q will be zero.
And for a lowpass filter it will always be 1/2.
As a result, Q is not used for HighPass or Lowpass analog filters.