Dissolve picolinic acid in THF, add 1.2 e.q. of CDI (carbonyldiimidazole), heat to reflux for 1-3 hours. Allow to cool to room temperature then add 3 equivalents of powdered imidazole and 3 equivalents of powdered NH2OH.HCl. Stir overnight.

Add pH 7 buffer then extract with EtOAc.

Thanks a lot Eric! picolinic acid and CDI  should be at equal stoichiometry, is that what you meant by e.q.?

e.q. is short hand for equivalents. It is often worth using a marginal excess (1.1 or 1.2 equivalents) of CDI as in practical situations it can be of variable quality and is quite moisture sensitive.

If you have very good quality CDI, flame dried glassware and truly anhydrous THF then you could use exactly 1 equivalent. I found that the excess hydroxylamine hydrochloride and added imidazole helped with the system I was working with.