I need the components of a simple method to determine Vitamine 25 OH
D3 in HPLC.The method is as follow:

Sample preparation

Mix briefly 500 µl serum/plasma with 50 µl Internal Standard in a
light protected reaction vial.
Add 500 µl Precipitation Reagent, vortex 20 s.
Cool down 10 min at +4 °C.
Centrifuge 5 min at 13 000 rpm.
Apply entire supernatant to sample clean up column, centrifuge 1 min
at 1500 rpm, discard effluent.
Draw 2 x 1 ml Wash Buffer 1 through the column by centrifugation (1
min at 1500 rpm), discard effluent.
Draw 75 µl Wash Buffer 2 through column by centrifugation (1 min at
1500 rpm), discard effluent.
Elute with 200 µl Elution Buffer into glass vials (1 min at 1500 rpm),
dilute with 20 µl dist. water.
Inject 50 µl eluate into the HPLC system.

What are the names of these components according to you?

Thanks

Dr Gianfranco Bruno
Italy