The CheqSol method for measuring solubility was discovered at Sirius in 2004 and is covered by patents in the US, EU and Japan, and is well suited for compounds whose unionised form readily crystallises. The Curve-Fitting method later evolved for measuring samples whose unionised form exists in liquid or amorphous form.
For a clear review of our solubility methods, see our 2011 Webinar on “How CheqSol works”, available from the Downloads section of this web site. See also our 2011 webinar on “Techniques for investigating supersaturation and the enhancement of solubility” which reviews the use of CheqSol for studying solubility enhancement.
We validated the Sirius pH-metric CheqSol and Curve-Fitting solubility methods against published values determined by shake-flask in 2006 in a study of 16 compounds:
Box, K. J.; Völgyi, G.; Baka, E.; Stuart, M.; Takács-Novák, K.; Comer, J. E., Equilibrium versus kinetic measurements of aqueous solubility, and the ability of compounds to supersaturate in solution--a validation study. J Pharm Sci 2006, 95 (6), 1298-307.
Much of the current research at Sirius and our collaboration partners involves the use of CheqSol. Our most recent solubility results may be found in six of our 12 posters presented at the AAPS 2012 Annual Meeting. These posters are available from the Downloads section of this web site, where you can also find applications notes on Solubility and Supersaturation, and CheqSol explained.
The graph below compares 11 intrinsic solubility values measured on SiriusT3 with published measured values.