Abstract: In preparing a sample of a liquid material, particularly a sample suitable for chromatographic analysis, an apparatus and method are provided whereby dissolved precipitatable material is removed from the liquid material by precipitation followed by filtering to obtain a liquid sample which can be suitably analyzed. In a preferred embodiment a combination of dilution and cooling are used to precipitate trinitrotoluene from a solution containing sulfuric and nitric acids prior to the chromatographic analysis of the remaining sample liquid material.