Calculation of Lignin Concentration from Porosity

Relative lignin concentration can then be calculated using the following equation  

Three quantitative approaches to measure lignin distribution are interference microscopy, UV microscopy, and bromination/EDXA. The choice of method probably depends more on the availability of equipment than any other factor since each method can be applied to a similar range of specimen types. 

UV microscopy has been used most extensively due to the pioneering work of Goring and others (Fergus et al. 1969, Scott et al. 1969). No specific comparison has been made between UV microscopy and interference microscopy. Interference microscopy gives consistently lower values than UV microscopy when compared on a w/w basis (Table 4.3.1). 

Bromination/EDXA (Chap. 4.4) has several disadvantages when compared to the other two techniques. Only relative lignin concentration can be determined directly by this method and a correction factor of 1.7 is required to obtain agreement between techniques (Saka et al. 1982, Donaldson and Ryan 1987). When bromination/EDXA and interference microscopy are used on matched samples, agreement is poor (Donaldson and Ryan 1987) as shown in Table 4.3.2. Not only is there poor quantitative agreement between the two methods, but EDXA data are also much more variable within each specimen. 

---