Trace detection of glycolic acid by electrophore labeling gas chromatography-electron capture mass spectrometry

As little as 10 pg of standard glycolic acid (glycolate) was detected in a method comprising the following sequence of steps: (1) add glycolate-2,2-d(2) as an internal standard and exchange the carboxylate oxygens in hot HCl/[(18)O]water; (2) form an amide derivative with a water-soluble carbodiimide and the electrophoric amine, AMACE1; (3) purify by bypass HPLC; (4) derivatize the residual hydroxy with butyric anhydride; (5) partition with acetonitrile/2 M NaCl; and (6) detect by GC-ECMS. At an intermediate stage in method development, 1 pg of glycolate-2,2,-d(2) could be detected by subjecting it to the above steps 2-6, forming product in an overall, absolute yield of 76%. Step 1 was added after an effort to fully overcome background contamination by glycolate was unsuccessful. For example, background contamination by glycolate could increase rather than decrease when the methanol reagent in the procedure was "carefully purified." The work extends the sensitivity for glycolate detection by approximately 100-fold and provides high-performance conditions for the analytical steps employed.