Manual of methods of pesticide residues analysis of food commodities

One of the significant areas in which pesticide residue analysis differs significantly from macro-analysis is that of contamination and interference. Trace amounts of contamination in the final samples used for the determination stage of the method can give rise to errors such as false positive or false negative results or to a loss of sensitivity that may prevent the residue from being detected. Contamination may arise from almost anything that is used, for or is associated with, sampling, sample transport and storage, and the analysis. All glassware, reagents, organic solvents and water should be checked for possible interfering contaminations before use, by analysis of a reagentblank.