Sample preparation for inositol measurement: Sep-Pak C18 use in detergent removal

The enzymatic-fluorometric method of myo-inositol quantitation by L.C. MacGregor and F.M. Matschinsky (1984, Anal. Biochem. 141, 382-389) has proved to be very useful in accurately measuring small amounts of myo-inositol. Although this procedure is quite satisfactory, relatively high concentrations of detergents, salts, NADH, and malate interfere. To extend the usefulness of the MacGregor and Matschinsky method we report here an extraction procedure which removed the interfering substances, yet allowed the recovery of close to 100% of the inositol. The procedure involved first passing the sample through a Sep-Pak C18 cartridge to remove detergent and then through a mixed-bed resin to remove the ionic constituents. The procedure with the Sep-Pak C18 cartridge is applicable to a wide variety of biological samples requiring detergent removal.