Aldehyde content of cellulose determined by Benedict’s solution and visible absorption of copper(II)-EDTA complex

Abstract

Benedict’s solution was employed to determine the aldehyde content of a cellulose paper. Benedict’s solution, containing Cu(II), citrate and carbonate, is capable of selectively oxidizing the aldehyde groups of cellulose and producing cuprous oxide. The selective oxidation was conducted at room temperature for an extended period of time. The aldehyde content was derived from the change of the Cu(II) concentration. The Cu(II) concentration was determined by measuring the 750 nm radiation absorption of the complex of Cu(II)-ethylene diamine tetraacetic acid (EDTA). The interferences from citrate, carbonate and foreign metallic cations on the 750 nm absorption measurement were also examined. The results showed that the interferences of citrate and carbonate can be removed via the dilution of Benedict’s solution. Also, the absorption due to the Cu(II)-EDTA complex was observed to be far superior to those of the EDTA complexes of the foreign metallic cations. The foreign metallic cations had a limited interference on the 750 nm absorption measurement. Benedict’s solution, together with the 750 nm absorption method, is hence a reliable approach for determining the aldehyde content of cellulose.