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Licensed Unlicensed Requires Authentication Published by De Gruyter July 8, 2011

Study of stilbene and resin acid content of Scots pine heartwood by electrical impedance spectroscopy (EIS)

Laura Tomppo, Markku Tiitta, Tapio Laakso, Anni Harju, Martti Venäläinen and Reijo Lappalainen
From the journal

Abstract

Scots pine (Pinus sylvestris L.) heartwood samples were measured with electrical impedance spectroscopy (EIS) at frequency range 1 Hz–10 MHz in green and relative humidity (RH) 65% conditioned moisture content (MC) after oven-drying. Complex impedance parameters were studied in relation to the density, moisture, resin acid and stilbene contents. The measurements were conducted in tangential (T) and longitudinal (L) directions with 36 samples in each analysis. For green MC, there were significant correlations between impedance phase angle and contents of stilbenes and resin acids at frequencies below 400 Hz. For the resin acid content, the strongest correlation with phase-angleT was -0.45 (P<0.01) at 100 Hz. Impedance magnitude correlated significantly with MC throughout the frequency range, e.g., at 10 kHz, r was -0.71 (P<0.001) for L-direction. In moisture conditioned state, the correlation between stilbenes and T-measured phase angle was strongest at 250 Hz, (r=-0.56, P<0.001). Equivalent circuit model of two ZARC-Cole elements in series was fitted for the measurements in green MC. Several model parameters correlated with MC (e.g., R1, L r=-0.64, P<0.001), but only one parameter correlated weakly with stilbene content (R2, T r=0.35, P<0.05). The study shows that EIS has a potential for independent determination of resin acid or stilbene contents and MC for green pine heartwood.


Corresponding author. Department of Applied Physics, University of Eastern Finland, FI-70211 Kuopio, Finland Phone: +358 (0) 40 355 2541 Fax: +358 (0) 17 16 2585

Received: 2010-9-3
Accepted: 2011-5-5
Published Online: 2011-07-08
Published Online: 2011-07-7
Published in Print: 2011-08-01

©2011 by Walter de Gruyter Berlin Boston

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