Sample preparation for β-exotoxin determination in Bacillus thuringiensis cultures by reversed-phase high-performance liquid chromatography

beta -Exotoxin is a nucleotide analogue produced by the entomopathogenic bacterium Bacillus thuringiensis. We have defined two new HPLC procedures for quantification of this exotoxin in culture supernatants of B. thuringiensis grown in poor or rich medium. The sample is prepared either by precipitation in solvent or by solid-phase extraction. Solvent precipitation is achieved treating the sample with acetone and acetonitrile. Solid-phase extraction is performed with a C-18 and an anion-exchange cartridge. Reversed-phase HPLC with gradient elution of the prepared samples gives a limit of quantitation of 2 mug/ml for samples prepared by solvent precipitation and of 0.3 mug/ml for samples prepared by solid-phase extraction. (C) 2001 Academic Press.