[Study on certified reference material of benzene, toluene, o-xylene in charcoal].

This certified reference material (CRM) of benzene, toluene and o-xylene in charcoal is used for quility control and calibration of analytical instruments in the determination of benzene, toluene and o-xylene in air. Homogeneity of benzene, toluene and o-xylene concentrations in the CRM was testes by GC. The stability of the CRM was assessed for one year. The certified values are based on analysis made by a group of independent laboratoies using GC method.