A comparison of six methods of estimating lignin in grass hay

The purpose of the investigation was to determine which of six of the commonly used methods for the determination of lignin give the most reproducible results and which yield the purest lignins. The methods were compared on the basis of the yields of residues obtained after organic‐solvent extraction and after total ‘pre‐treatment’, as well as yields of ash‐free lignin. The lignin residues were also analysed for carbon, nitrogen, methoxyl, N‐alkylamide and ash content. It was found that there was little to choose between three of the methods which gave mean values between 7.1 and 7.8% of ash‐free lignin, but the other three methods, which gave mean values of 9.5, 10.7 and 14.6% of lignin were much less reliable. Attention is drawn to the need for authors to give details of methods employed in the determination of lignin.