Organic compounds (OrgAlk) are currently unaccounted for in the marine inorganic carbonate model; the presence of which may be contributing to pH-dependent discrepancies when using dissolved inorganic carbon (DIC) and total alkalinity (TA) to calculate pH. It has been hypothesized that unaccounted-for OrgAlk contributing to TA could contribute to this discrepancy. To test this hypothesis, we developed a novel methodology to accurately quantify the presence of OrgAlk (pKa range 3-5) in seawaters. Titration methods with different end-points are used on the same seawater batch, and the difference in TA (ΔTA) between the methods is used to quantify OrgAlk. The new methodology was validated through standard additions of acetate and analysis of five batches of seawater reference materials (RMs). The OrgAlk in the seawater RMs was on average 2.54 ± 0.60 µmol/kg. Ocean seawater samples were collected 33 miles offshore from Monterey Bay and analyzed, to a depth of 1,400m, showing a near-constant water column OrgAlk concentration of 1.5 µmol/kg. This work is a major step forward to understanding and correcting the pH-dependent discrepancy in the marine inorganic carbonate system, highlighting that OrgAlk, which appears to be ubiquitous in ocean seawaters, and its contributions to TA can no longer be ignored.