pION uses industry standard methods for measurement of ionization constants (pK_as). We can analyze up to 10 overlapping pK_as and can distinguish protogenic counter-ions. Sparingly soluble compounds may be analyzed in mixtures of an organic solvent (such as methanol or DMSO) and the aqueous pK_a extrapolated.

Our potentiometric and spectrophotometric methods have obtained pK_as as low as 1.0 and as high as 13.0. Using standard potentiometric procedures, we routinely measure pK_as between 2.0 and 12.0 for compounds not requiring a cosolvent and between 3.0 and 11.0 for compounds whose aqueous pK_a is extrapolated from cosolvent mixtures. If compound structure is appropriate, the spectrophotometric method is applied to measure pK_as of water soluble and insoluble compounds between 2.0 and 12.0.

• Fill out Sample Submittal Sheet for EACH compound (can be downloaded below)
• Obtain a purchase order number and include the number on the Sheet
• Send 7-10 mg of compound to pION
• For aqueous pK_a measurements, samples must be soluble over the pH range 3.0-11.0 to a level of at least 1 mg/10 mL (100 µg/mL)

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