Near infrared spectroscopy of permethrin or bifenthrin treated radiata pine (P. radiata D.Don) has been used to develop calibration models to later predict the active retention in unknown samples. Calibrations were developed for both a laboratory NIR and a portable NIR using laboratory-prepared calibration samples at a range of target retention levels. Correlations were established between the actual retention and NIR-predicted retention for both bifenthrin and permethrin with coefficients of determination of were 0.991 and 0.974 for bifenthrin and permethrin respectively for the calibration step and 0.74 and 0.87 with standard errors of prediction of 0.003 and 0.002 respectively for the validation step when using the laboratory NIR. These calibrations were then used for prediction of retention levels in run-of-mill samples.

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