PEER-REVIEWED ARTICLE bioresources.com Masingale et al. (2009). “Oxidant for lignin analysis,” BioResources 4(3), 1139-1146. 1139 AN OXIDANT TO REPLACE NITROBENZENE IN LIGNIN ANALYSIS Michael P. Masingale, a Ericka F. Alves, b Theresah N. Korbieh, b Samar K. Bose, b and Raymond C. Francis b* Four metal organic frameworks (MOFs) are being evaluated as possible catalysts for alkaline lignin oxidation. One aspect of the screening process is the oxidation of in-situ hardwood lignin by a high mole ratio of Cu, Fe, or Cu + Fe contained in the MOFs. The MOF’s were prepared in a microwave-assisted synthesis. One of the MOFs, a benzenetricar- boxylic acid complex of Cu (II) and Fe (III), converted the phenylpropane (C 9 ) units in in-situ poplar lignin to approximately 50% monomers. The ratio of syringyl (S) to guiacyl (G) monomers was similar to the S:G ratio obtained from nitrobenzene oxidation (NBO). The S:G ratio from NBO was then compared to that from MOF oxidation (MOFO) for two other poplars. The S:G ratios for the three poplars by MOFO were 1.20, 1.51 and 1.67, respectively while the corresponding NBO values were 1.25, 1.45 and 1.68. These initial results indicate that MOFO could be developed into a credible replacement for NBO, because it affords a higher yield of monomers when a large MOF dose is used. Some preliminary results are also presented for MOF acting as a catalyst (100 ppm Cu (II) plus 81 ppm Fe (III) in NaOH) for oxygenation of the hardwoods. The products from O 2 + MOF are identical to MOF only, but the ratios amongst them are different. Keywords: Metal organic frameworks; Metal oxides; S:G ratio; Hardwoods; Lignin oxidation. Contact information: a: Department of Chemistry and Physics, Le Moyne College, 1419 Salt Springs Road, Syracuse, New York, USA, 13214; b: Department of Paper and Bioprocess Engineering (PBE) and the Empire State Paper Research Institute (ESPRI), SUNY College of Environmental Science & Forestry, 1 Forestry Drive, Syracuse, New York USA 13210. * Corresponding author: Tel: 1-315-470-6525; Fax: 1-315-470-6945; e-mail address: francis@syr.edu INTRODUCTION Four metal organic frameworks (MOFs) are being evaluated as possible catalysts in our laboratories. The reaction of interest is lignin oxidation by oxygen in hot alkali to produce the four monomers shown in Fig. 1. One aspect of the screening process is straight oxidation of in-situ lignin in milled hardwood with a high mole ratio of Cu (II), Fe (III), or Cu (II) + Fe (III) to phenylpropane (C 9 ) units. The Cu (II) or Fe (III) would be obtained from CuO, Fe 2 O 3 , or the MOFs. One of the MOFs gave a higher total yield of the products in Fig. 1 than was obtained with nitrobenzene oxidation (NBO), and the ratio of (S1 + S2)/(G1 + G2) appeared to be similar. A new project was initiated to see if MOFO could replace NBO in determining the syringyl to guaiacyl (S:G) ratio of hardwood and other lignins. Nitrobenzene is a liquid with low volatility at room temperature but is a confirmed