Drawbacks in the use of 23-nor-deoxycholic acid standards

23-Nor-deoxycholic acid is widely used as internal standard in gas-liquid chromatographic studies of bile acids. Two batches of this compound, submitted to conventional alkaline hydrolysis of bile acid conjugates, were found to be transformed into a product with chromatographic properties different from those of ''authentic'' 23-nor-deoxycholic acid. To identify this ''new'' product a comparison was made between chromatographic properties, mass spectra, and NMR spectra of 23-nor-deoxycholic acid before and after alkaline hydrolysis. The results indicate that the ''new'' compound is the true 23-nor-deoxycholic acid while the product present in the two batches examined is a monoacetate derivative.