Explain x-ray fluoresence vs. mass spectroscopy for analysis of boron

First, is it correct to say that XRF measurement applies only to metals and transitional metals in the periodic chart? In otherwords, XRF can only be used to measure ppm levels of metals in solution etc. etc. For instance, zinc and aluminum could be measured with XRF.

What about a non-metal like boron ---- why can't XRF truly be used to measure concentration of boron.....especially when boron and zinc have somewhat similar first ionization energies?

Would boron be measured by mass-spec?? And how would that actually work?

Thank you