A new approach for the isolation of cellulose from aquatic plant tissue and freshwater sediments for stable isotope analysis

Isotope studies of the cellulose of plant tissue and sediments are increasingly important in ecological and palaeoenvironmental studies. The reliability of analytical results in these investigations depends on the ability to separate pure cellulose from the organic and inorganic matrix. This study evaluates the performance of a new approach for the isolation of cellulose based on wet oxidation and cellulose dissolution in cuprammonium solution (CUAM) with respect to conventional techniques using solely wet oxidation or wet oxidation in combination with density separation. All the methods led to identical changes in isotopic composition of standard cellulose powder samples, providing evidence that CUAM-treated cellulose is isotopically indistinguishable from cellulose treated with conventional methods. The performance of CUAM with aquatic plant tissue was at least equal to those of the other methods used and in numerous cases achieved better results in terms of cellulose purification and precision of the isotope signal. Compared to conventional methods, contamination of several samples with small amounts of minerogenic matter and biogenic opal could be completely removed from the extraction residue with CUAM. While conventional methods failed to result in isolation of cellulose from two typical fine-grained lacustrine sediments, extraction residues from CUAM treatments revealed infrared (IR) spectra resembling those of standard cellulose powder, without evidence of minerogenic matter, biogenic opal, chitin or refractory organic matter. A series of sedimentary materials ranging from soil, to sediment trap and sediment core material were extracted with CUAM. IR spectra of all materials tested correspond to cellulose, and carbon and oxygen isotope compositions of the extracted cellulose fractions agreed with previous knowledge about the samples. Our results prove that CUAM is a reliable method that yields clean and pure cellulose for high quality isotope analysis from plant tissue and different types of sediments alike. (C) 2008 Elsevier Ltd. All rights reserved.