Determination of didealkylatrazine in water by graphitized carbon black extraction followed by gas chromatography-high resolution mass spectrometry

A highly specific and sensitive method has been developed for determining trace levels of didealkylatrazine (DDA), one of the dealkylated products of atrazine degradation occurring in ground and surface waters. The analyte was isolated efficiently from deionized water and ground water by liquid-solid extraction via a graphitized carbon black cartridge, and the recoveries are greater than 80%. These recoveries are an order of magnitude greater than those achieved by liquid-liquid extraction (dichloromethane) and solid-phase extraction with a C₁₈ bonded silica cartridge. Analysis was performed by gas chromatography-high resolution mass spectrometry; mass profiles were acquired in the selected ion monitoring mode. A precision of < 20% (relative standard deviation) was obtained for six deionized water samples fortified with DDA at the 500 ppt level. The average accuracy is 85% of the true amount for the deionized water samples. The detection limit for a 200-ml sample is 2 ppt. The method has been successfully applied to determine DDA in ground water.