DETERMINATION OF D/H RATIOS OF NONEXCHANGEABLE HYDROGEN IN CELLULOSE - A METHOD BASED ON THE CELLULOSE-WATER EXCHANGE-REACTION

We have established a simple technique for the determination of D/H ratios of nonexchangeable hydrogen in cellulose. This technique is based on equilibrating cellulose prepared from raw wood or cotton with water of known isotopic composition. A temperature of 0-degrees-C was selected for the exchange experiments. This allowed the rapid freezing and subsequent sublimation of the ice without affecting the isotopic composition of the equilibrated hydroxyl hydrogen. A sodium hydroxide treatment of the cellulose is necessary to achieve equilibrium between cellulose and water within 24 hours. The best sodium hydroxide treatment procedure was found to be overnight soaking of cellulose in a 17% NaOH solution at near 0-degrees-C, followed by rinsing and transferring the cellulose to the exchange vessels without drying. We have obtained a very good reproducibility for the deltaD analysis of the equilibrated cellulose treated with this procedure (1 sigma < 2 parts per thousand). The resulting deltaD values of nonexchangeable hydrogen, using the equilibration technique, were compared with those obtained using the nitration technique. The agreement between the two techniques is +/-3.3 part per thousand (1sigma), and the analytical accuracy of the equilibration method is +/-2.5 parts per thousand (1sigma). This method may be useful in dealing with the nitration of ancient plant materials, which is sometimes not possible. In addition, the technique may be extended to the isotopic analysis of other organic compounds that contain exchangeable hydrogen.