Application of TLC for Confirmation and Screening of Pesticide Residues in Fruits, Vegetables, and Cereal Grains: Part 2. Repeatability and Reproducibility of Rf and MDQ Values

Abstract This paper illustrates the effect of major factors influencing the reproducibility of thin layer chromatography (TLC) separation and detection under largely differing environmental and laboratory conditions. The optimum conditions for reproducibility and detection sensitivity was obtained on 20 × 20 cm layer in the retention factor (Rf) range of 0.2–0.7 by applying the sample in spots of 3–4 mm diameter at 2 cm from the edge of the plate. The reproducibility rapidly decreased below Rf = 0.2. Above Rf = 0.2 the within-laboratory reproducibility of 219 pesticides obtained in ethyl acetate silica gel elution system by several laboratories was typically below 10%. The among-laboratories reproducibility of the average retention factors was generally below 12%. The minimum detectable quantities (MDQ) of 219 pesticide residues were determined with nine detection methods. The MDQ values largely varied depending on the mode of detection. Bioassay methods enabled the detection down to 0.1–10 ng, while 20–1...