include but are not limited to water and water based solutions the chemically active substance utilized in the process of the present invention is preferably a substance which will aid in the destruction of sample matrix components which would otherwise interfere with the release of tcdd into the vapor phase during boiling and or subsequent extraction of tcdd from the condensate the chemically active substance should preferably increase the hydroxide ion concentration in the aqueous sample matrix impart alkalinity preferably in an amount at least equivalent to 0 5n sodium hydroxide but not stronger than 2n sodium hydroxide in ability to promote base catalyzed hydrolysis suitable chemically active substances include but are not limited to an alkali hydroxide such as sodium hydroxide potassium hydroxide cesium hydroxide or lithium hydroxide a preferred chemically active substance is 1n potassium hydroxide the chemically active substance may be added to the diluent prior to its addition to the aqueous sample matrix to form a diluent composition which is utilized to dilute and react with the aqueous sample matrix the amount of diluent composition utilized in the process of the present invention should be an amount sufficient to permit the extraction of tcdd from the aqueous sample matrix generally 100 to 250 milliliters ml of diluent composition is utilized per ml of aqueous sample matrix alternatively the diluent and chemically active substance may be sequentially added to the aqueous sample matrix in this case the total volume of diluent and chemically active substance would also equal 100 to 250 milliliters ml of diluent composition per ml of aqueous sample matrix 0 1 to 100 picograms preferably 1 to.