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