Variation of cypermethrin residue levels in selected tropical fruit samples within and among field trials.
A comparison of pesticide residue data from field trials of three sampling methods was done to assess the variability of cypermethrin residue levels in terms of within the field trial and among between field trials. The fruit (mango/ papaya) samples were collected on individual tree basis (Study A: within field trial), on subplot basis (Study B: within field trial) and whole plot basis (Study C: among field trials). The field trials were conducted from 2006 – 2009. In Study A and B, replicate analysis yielded smaller measurement variation compared to sample replicates. Measurement of variation was highest (Relative Standard Deviations, RSD = 50.7%) among field trial samples (Study C) followed by samples from Study A (RSD = 28.9%) and Study B (RSD = 15.8%). The RSD of replicate samples were higher than the RSD of the analysis of replicates in Study A and B. The contributors of uncertainty to the measurement of cypermethrin residue in descending order, based on percentage variance were: sampling (82.2 – 95.6%) followed by sample processing (2.6 – 11.5%) and analysis (1.7 – 6.3%). The field factor was a significant contributor to the variation in pesticide residue measurement as compared to the laboratory factor.