We determined that the most reliable way to prepare dissolved 15N2 gas standards involves equilibration of the liquid phase with a headspace, rather than injection of a 15N2 gas aliquot into a sealed bottle without a headspace. Standards were prepared in a room with a relatively constant ambient temperature. Serial aliquots of 15N2 gas were each injected into the headspace of crimp-sealed 120 mL serum bottles containing 80 mL of air-equilibrated seawater (at room temperature) and a stir bar with an unpressurized air headspace. The vials were equilibrated for 72 hours on a stir plate (at low rpm) prior to analysis on the MIMS or IRMS.