Resin acid markers for total resin acid content of in-mill process lines of a TMP/CTMP pulp mill

Resin acids are a class of lipophilic extractives present in process waters of pulp and paper mills using softwoods as a furnish. These compounds caus e pitch problems and adversely affect paper properties. As pulp;ind paper m ills move toward water systems closure the concentration of these extractiv es are expected to increase. Therefore, it will become more important to mo nitor and control extractives content in the process lines of pulp and pape r mills. Resin acids are traditionally analyzed by gas chromatography (GC). This method of analysis requires extracting the analytes from a sample mat rix, separating by solid phase extraction and derivatizing the resin acids to increase their volatility. Although this process; is tedious and expensi ve and cannot be used as an on-line monitoring system, it does provide quan tification of the individual resin acids with a low detection limit. Findin g marker compounds for the total resin acid content of an in-mill process w ater sample may aid in the development of a fast and reliable monitoring sy stem. A preliminary GC analysis of 25 in-mill process water samples establi shed abietic acid as the best single marker for total resin acid content. A correlation of 0.964 was found between the abietic acid concentration and the total resin acid content of these samples. This result led to the analy sis of 167 samples from a previous audit of resin acid content of in-mill p rocess water samples. Abietic acid was the single best marker for these sam ples as well with a correlation of 0.928. An improved correlation of 0.957 was obtained if a combination of isopimaric and abietic: acid contents was used as the marker for total resin acid content. Dehydroabietic acid, which has been shown to be a good marker for total resin, acid content of mill e ffluent samples, was al poor marker for in-mill samples. A correlation of o nly 0.664 was obtained between DHA and total resin acid content of the samp les analyzed. (C) 2000 Elsevier Science Ltd. All rights reserved.