Green sawn timber surfaces of the softwood Caribbean pine and the hardwood white cheesewood were treated by dipping, spraying, and precise spiking with the antisapstain product NeXgen. After storing for either two hours or two weeks, the treated surfaces were sampled by one of four alternative protocols, which included two involving a square wad sampling punch (one hit or six hits), one involving an electric planer, and one reference technique where the surface zone was removed and cut on a band-saw. Surface samples were extracted into an azeotropic mixture of acetonitrile and methanol before analysis by high performance liquid chromatography for the active ingredient chlorothalonil.
There was little difference in variability between the protocols; coefficients of variation from spiked surfaces varied f rom 3% to 9%. Recovery of spikes varied from 49% to 101%, with efficiency generally better from fresh than dried surfaces, better from softwood than from hardwood surfaces, and better using the single-punch than alternative protocols. Efficiencies of the single-punch protocol were 92% (fresh hardwood), 93% (dried hardwood), 100% (dried softwood) and 101% (fresh softwood).
As expected, the inherent variability of surface concentrations produced under dipping and spraying conditions prevented firm conclusions being drawn from these studies, but the single-punch protocol which was superior in the spiking studies generally ranked higher than the alternatives in efficiency on dipped and sprayed surfaces also. The single-punch protocol is recommended for use on both softwood and hardwood surfaces in both freshly-treated and dried condition.
Keywords: CARIBBEAN PINE; WHITE CHEESEWOOD; ANTISAPSTAIN; NEXGEN; SAMPLING; ANALYSIS; CHLOROTHALONIL
Conference: 98-06-14/19 Maastricht, The Low Countries