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We now have a number of reference standards available as solution in flame sealed vials. The potency for each was independently confirmed using 500 MHz quantitative proton NMR (Q-NMR) analysis - this technique detects and determines concentration (in mg/mL) of the active component in the solution in a completely independent and accurate process.  This is so because the detector response (NMR integral intensity) is identical whether it be a major component or an impurity.  Most other analytical techniques suffer from a major problem that detection response for distinct molecules can be different.  Hence, we can claim that our analytical reference standard solutions have the most accurate potency values and will provide more accurate values in your assays compared to when our competitor reference solutions are used.  We have put in significant effort in minimizing error in our custom Q-NMR methods.  The largest error is from weighing uncertainty, which is minimized whenever larger quantity is weighed for the dilution.  Our custom Q-NMR method for determination of potency in dilute solutions in more accurate than for powders since the weighing errors are significantly minimized.