Study of a new matrix certified reference material for simultaneous measurement of two plant growth regulators residues in tomato

A new matrix certified reference material (CRM) was developed for analysis of chlormequat chloride (CCC) and 2,4-dichlorophenoxyacetic acid (2,4-D) residues in tomato pulp. A tomato pulp CRM candidate with the same matrix composition and similar residues concentration level to the real sample was prepared by means of adding drugs. Liquid chromatography tandem isotope dilution mass spectrometry (ID-LC-MS/MS) was established to accurately determinate CCC and 2,4-D residues in tomato pulp CRM candidates. The characterization of mass fractions of CCC and 2,4-D in tomato pulp were conducted by 8 laboratories. The certified values for CCC and 2,4-D were assigned to be 4.1 mg/kg and 1.9 mg/kg, with expanded uncertainties of 0.4 mg/kg and 0.3 mg/kg at a confidence level of 95 % (coverage factor k = 2), respectively. The results of homogeneity testing show that the CRM was homogeneous for CCC and 2,4-D between and within bottles. The stability monitoring results indicated that the CRM could be stable for 14 months at −20 °C storage temperature and for 9 days under 30 °C transportation condition. The developed CRM has been authorized and numbered as GBW(E)100919. It would be conductive to method validation in the residues monitoring of CCC and 2,4-D in fruits and vegetable products.