Leukotriene B4-d4 (LTB4-d4) is intended for use as an internal standard for the quantification of leukotriene B4 (LTB4) by GC- or LC-MS. Leukotriene B4 (LTB4) is a dihydroxy fatty acid derived from arachidonic acid through the 5-lipoxygenase (5-LO) pathway.^1,2,3 It promotes a number of leukocyte functions including aggregation, stimulation of ion fluxes, enhancement of lysosomal enzyme release, superoxide anion production, chemotaxis, and chemokinesis. In subnanomolar ranges (3.9 x 10−10 M), LTB4 induces chemotaxis and chemokinesis in human polymorphonuclear leukocytes.⁴ At higher concentrations, (1.0 x 10−7 M), LTB4 leads to neutrophil aggregation and degranulation as well as superoxide anion production.^4,5 LTB4-d4 MaxSpec® standard is a quantitative grade standard of LTB4-d4 that has been prepared specifically for mass spectrometry and related applications where quantitative reproducibility is required. The solution has been prepared gravimetrically and is supplied in a deactivated glass ampule sealed under argon. The concentration was verified by comparison to an independently prepared calibration standard. This LTB4-d4 MaxSpec® standard is guaranteed to meet identity, purity, stability, and concentration specifications and is provided with a batch-specific certificate of analysis. Ongoing stability testing is performed to ensure the concentration remains accurate throughout the shelf life of the product. Note: The amount of solution added to the vial is in excess of the listed amount. Therefore, it is necessary to accurately measure volumes for preparation of calibration standards. Follow recommended storage and handling conditions to maintain product quality.