Fig. 4

GC/MS chromatograms obtained with the double derivatization procedure for a desk coating sample (DHU); b sample from a pulpit (B53). Inverted triangle: DHA isomers; white circle: di-DHA isomers; minus: abietanes; plus: pimaranes

GC/MS chromatograms obtained with the double derivatization procedure for a desk coating sample (DHU); b sample from a pulpit (B53). Inverted triangle: DHA isomers; white circle: di-DHA isomers; minus: abietanes; plus: pimaranes