The PGE2 Quant-PAK has been designed for the convenient, precise quantification of PGE2 by GC- or LC-MS. It includes a 50 µg vial of PGE2-d4 and a precisely weighed vial of unlabeled PGE2, with the precise weight (2-4 mg) indicated on the vial. This unlabeled PGE2 can be used to quantify the PGE2-d4 standard by constructing a standard curve of peak intensity ratios (deuterated versus unlabeled).