De or het eiwitbepaling?

The correct Dutch article is:

de eiwitbepaling

Rule Words ending in -ing: almost always de. See the rule

How to use eiwitbepaling

the eiwitbepalingde eiwitbepaling
this eiwitbepalingdeze eiwitbepaling
that eiwitbepalingdie eiwitbepaling
our eiwitbepalingonze eiwitbepaling
your eiwitbepalingjouw eiwitbepaling
every eiwitbepalingelke eiwitbepaling
which eiwitbepaling?welke eiwitbepaling?
a big eiwitbepaling / the big eiwitbepalingeen grote eiwitbepaling, de grote eiwitbepaling