The PGD2 Quant-PAK has been designed for the convenient, precise quantification of PGD2 by GC- or LC-MS. It includes a 50 μg vial of PGD2-d4 and a precisely weighed vial of unlabeled PGD2, with the precise weight indicated on the vial. This unlabeled PGD2can be used to quantify the PGD2-d4 standard by constructing a standard curve of peak intensity ratios (deuterated versus unlabeled).