The PGF2α Quant-PAK has been designed for the convenient, precise quantification of PGF2α by GC- or LC-MS. It includes a 50 μg vial of PGF2α-d4 and a precisely weighed vial of unlabeled PGF2α, with the precise weight (2-4 mg) indicated on the vial. This unlabeled PGF2α can be used to quantify the PGF2α-d4 standard by constructing a standard curve of peak intensity ratios (deuterated versus unlabeled).