The prostaglandin B2 (PGB2) Quant-PAK has been designed for the convenient, precise quantification of PGB2 by GC- or LC-MS. It includes a 50 µg vial of PGB2-d4 and a precisely weighed vial of unlabeled PGB2, with the precise weight indicated on the vial. This unlabeled PGB2 can be used to quantify the PGB2-d4 standard by constructing a standard curve of peak intensity ratios (deuterated versus unlabeled).