Two-dimensional high performance liquid chromatography for the separation of complex mixtures of explosives and their by-products

The insufficient ability of one dimensional HPLC to separate complex mixtures such as environmental samples can be overcome by using two dimensional systems combining columns with alternative/orthogonal selectivities Such a system for the separation of complex mixtures of explosives, their by-products and degradation products from environmental samples was developed and evaluated. It makes use of the different retention characteristics of an alkyl modified silica and a safrol modified silica in the reversed phase mode. The high peak capacity of two dimensional systems predicted by theory was realized employing a flexible switching technique and utilizing differences in the elution strength of the mobile phases. Thus, peak compression on the head of the second column was exploited. The efficiency of the two dimensional system was demonstrated for the separation of a complex mixture of nitroaromatic reference compounds. Furthermore, the system was applied to separate and identify nitro and nitroamino organic compounds in a groundwater sample from a former ammunition plant.