PtdIns-(3)-P1 (1,2-dipalmitoyl)-d62 (ammonium salt) is intended for use as an internal standard for the quantification of PtdIns-(3)-P1 (1,2-dipalmitoyl) (ammonium salt) by GC- or LC-mass spectrometry. The phosphatidylinositol (PtdIns) phosphates represent a small percentage of total membrane phospholipids. However, they play a critical role in the generation and transmission of cellular signals.{4096,8344} PtdIns-(3)-P1 (1,2-dipalmitoyl)-d62 is a synthetic analog of natural PtdIns featuring deuterated C16:0 fatty acids at the sn-1 and sn-2 positions. It is intended for use as an internal standard for the quantification of PtdIns-(3)-P1 by GC- or LC-mass spectrometry. This synthetic standard compound contains the same inositol and diacyl glycerol (DAG) stereochemistry as that of the natural compound.