Conventional Methods for Carbonyl Analysis in Celluloses

The quantitation of carbonyl groups in cellulose was so far limited to the measurement of the total carbonyl content by different methods, which are summarized in Table 1. 

The so-called copper number is still the method of choice in the pulp and paper industry in process control, but sometimes also in the research lab. The reducing power of cellulose is measured by reaction with an alkaline Cun-salt under defined conditions, the formed Cu1 ions can be titrated after re-oxidation [82]. The underlying reaction mechanisms are still not entirely understood, neither are the types of oxidized structures recorded. However, even though the copper number is only a sum-parameter, the data of which cannot be directly linked to the quantity of a specific oxidized function, it remains a valuable parameter for control in a number of industrially relevant processes. 

Copper number (Unspecific) Reducing power Titration Only relative data, mechanism ill-defined [82] 

Hydrazinium- salt Formation of charged groups on cellulose Photometric Only semi-quantitative [88] 

Hydroxyl- amine Oximation Elemental analysis, photometric, titration Sensitivity depends highly [83,89] on detection mode  

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