RESIN ACID MARKERS FOR TOTAL RESIN ACID CONTENT OF IN-MILL PROCESS LINES OF A TMP/CTMP PULP MILL ALESSIO N. SERREQI, HECTOR GAMBOA, KEVIN STARK, JOHN N. SADDLER and COLETTE BREUIL* Chair of Forest Products Biotechnology, Department of Wood Science, Faculty of Forestry, University of British Columbia, 4041-2424 Main Mall, Vancouver, British Columbia, Canada, V6T 1Z4 (First received 1 April 1998; accepted in revised form 1 July 1999) AbstractÐResin acids are a class of lipophilic extractives present in process waters of pulp and paper mills using softwoods as a furnish. These compounds cause pitch problems and adversely aect paper properties. As pulp and paper mills move toward water systems closure the concentration of these extractives are expected to increase. Therefore, it will become more important to monitor and control extractives content in the process lines of pulp and paper mills. Resin acids are traditionally analyzed by gas chromatography (GC). This method of analysis requires extracting the analytes from a sample matrix, separating by solid phase extraction and derivatizing the resin acids to increase their volatility. Although this process is tedious and expensive and cannot be used as an on-line monitoring system, it does provide quanti®cation of the individual resin acids with a low detection limit. Finding marker compounds for the total resin acid content of an in-mill process water sample may aid in the development of a fast and reliable monitoring system. A preliminary GC analysis of 25 in-mill process water samples established 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 analysis of 167 samples from a previous audit of resin acid content of in-mill process water samples. Abietic acid was the single best marker for these samples 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uent samples, was a poor marker for in-mill samples. A correlation of only 0.664 was obtained between DHA and total resin acid content of the samples analyzed. # 2000 Elsevier Science Ltd. All rights reserved Key wordsÐgas chromatography, analysis, resin acid, abietic acid, isopimaric acid, dehydroabietic acid, process line, pulp and paper INTRODUCTION Pulp and paper mills worldwide are moving towards water systems closure to reduce fresh water usage and decrease the amount of euent released into the environment. Dissolved and colloidal sub- stances (DCS) are known to be released from wood during mechanical pulping processes and accumu- late in the white water system (Allen, 1975; JaÈ rvinen et al., 1980). One consequence of water systems closure will be elevated levels of DCS, therefore, mills must improve management of their in-mill water systems to maintain productivity and product quality (Cronin, 1996; Farlow, 1996). The dissolved and colloidal substances are mostly com- posed of lipophilic extractives, lignins, polysacchar- ides and inorganic materials (SjoÈstroÈm, 1990; Ekman et al., 1990). High levels of these materials are associated with problems such as pitch deposits, reduced paper strength and decreased brightness (Brandal and Lindheim, 1966; LindstroÈm et al., 1977). Accumulation of DCS in white water will be detrimental to paper machine runnability and paper quality. The various components in DCS have been shown to cause dierent eects on the paper mak- ing process and paper quality (Wearing et al., 1985; Francis and Ouchi, 1997). For example, resin acids are a class of lipid extractives associated with DCS and have been shown to reduce wet web strength properties (Zhang et al., 1999). Therefore, monitor- ing their levels in the process lines of mills moving toward water systems closure may become increas- ingly important. Pulp and paper mills using soft- woods as a furnish release resin acids from wood Wat. Res. Vol. 34, No. 5, pp. 1727±1733, 2000 # 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0043-1354/00/$ - see front matter 1727 www.elsevier.com/locate/watres PII: S0043-1354(99)00288-2 *Author to whom all correspondence should be addressed. Tel.: +1-604-822-9738; fax: +1-604-822-9104