Preparation and characterization of in-house reference material for four organochlorine pesticides in tea matrix

Abstract

Production and evaluation of in-house reference material for incurred residues of four organochlorine pesticides, named hexachlorobenzene, dicofol, pp′-DDE, and op′-DDT, in tea sample has been performed. Raw materials (tea samples) were confirmed to contain certain levels of incurred organochlorine pesticide residues by a validated gas chromatography–mass spectrometry method. After the materials had been milled and thoroughly mixed, 400 bottles each having 20 g sample were prepared and their homogeneity (within-bottle and bottle-to-bottle variation) was found to be sufficient. The materials demonstrated satisfying stability of four organochlorine pesticides in both short-term (30 days) and long-term (12 months) stability studies. The reference values were characterized using an accurate isotope dilution gas chromatography–mass spectrometry method. The mass fraction (± expanded uncertainty) of hexachlorobenzene, dicofol, pp′-DDE, and op′-DDT in the reference material was (2.1 ± 0.2) mg kg−1, (513.3 ± 31.3) mg kg−1, (8.3 ± 0.6) mg kg−1, and (14.9 ± 1.0) mg kg−1, respectively. The reference materials have been distributed for use in laboratory quality assurance.