What SPE method do you recommend for nitrofurans from milk?

You can use Strata X-C for the extraction of nitrofurans from milk.  They are basic at low pH.  Please follow the method outlined below as a starting point.  With some initial results, the method can be further optimized.

Pretreatment-

Dilute sample with 0.5 part of DI water.  Acidify sample with 1% formic acid.  Adjust sample pH to 1 (use more formic acid as needed).

To a Strata X-C cartridge,

Condition/equilibrate with 4 bed volumes of methanol, then DI water

Load pretreatment sample at 1 mL/min

Wash with 4 bed vol of 1% Formic acid aqueous solution

Wash with 4 bed vol of methanol

Dry cartridge on full vacuum for 10 minutes

Elute with 2x 4 bed vol of 5% NH4OH in MeOH/DI water, 1:1

Evaporate and reconstitute sample in initial mobile phase for analysis