Defines extraction processes and gas chromatographic methods to determine parathion, parathion-methyl and other organophosphorus compounds in surface, waste and drinking waters. Also suitable for determining other organic compounds. Range depends on the compound and water source and is typically up to 1 ug/I with a reporting limit of 0,01 ug/I for drinking waters which involve an extraction ratio of 1000 to 1. Extraction efficiencies are usually less than 100%. Bias will vary with extraction efficiency of a particular compound, type of water and method employed.