Mass fragmentographic determination of homovanillic and 4-hydroxy-3-methoxy mandelic acids in 50 microliter plasma.

A method is presented for the mass fragmentographic determination of homovanillic and 4-hydroxy-3-methoxy mandelic acids in 50 microliter plasma or serum. The values found in normal, healthy adults agree well with previously published reports which required, however, much larger plasma volumes. The method uses a simple ethyl acetate extraction from acidified plasma and a one-step derivatisation with trifluoroethanol and pentafluoropropionic anhydride. The deuterium-labelled analogues are used as internal standards.