The 8-iso-PGF2α Quant-PAK has been designed for the convenient, precise quantification of 8-iso-PGF2α by GC- or LC-mass spectrometry. It includes a 50 μg vial of 8-iso-PGF2α-d4 and a precisely weighed vial of unlabeled 8-iso-PGF2α, with the precise weight indicated on the vial. This unlabeled 8-iso-PGF2α can be used to quantify the 8-iso-PGF2α-d4 standard by constructing a standard curve of peak intensity ratios (deuterated versus unlabeled).