The 6-keto PGF1α Quant-PAK has been designed for the convenient, precise quantification of 6-keto PGF1α by GC- or LC-MS. It includes a 50 µg vial of 6-keto PGF1α-d4 and a precisely weighed vial of unlabeled 6-keto PGF1α, with the precise weight (2-4 mg) indicated on the vial. This unlabeled 6-keto PGF1α can be used to quantify the 6-keto PGF1α-d4 standard by constructing a standard curve of peak intensity ratios (deuterated versus unlabeled).