An Optimized Solid Phase Extraction Procedure for EPA Method 8081 and 8082 Analytes in Water

Drinking Water
Poster Presentation

Prepared by A. Abdelkaoui, R. Tashjian
United Chemical Technologies Inc, 2731 Bartram Rd, Bristol, PA, 19007, United States


Contact Information: [email protected]; 215-781-9255

ABSTRACT

EPA methods 8081 (Organochlorine pesticides by GC) and 8082 (Polychlorinated biphenyls by GC) [1-2] are hazardous waste test methods (SW-846) regulated under the Resource Conservation and Recovery Act (RCRA). These methods are performance based which allow analysts to modify the sampling and analytical approaches to meet the measurement requirements. In other words, these methods convey “what” needs to be accomplished but not prescriptively “how” [3]. For water samples in methods 8081 and 8082, liquid-liquid extraction and solid phase extraction (SPE) are allowed to extract the target analytes from various aqueous samples. EPA method 3535A outlines several solid phase extraction methods for different EPA methods including 8081 and 8082, which use C18 SPE disk for sample extraction, and elution with methylene chloride (DCM), a toxic chlorinated solvent which needs solvent exchange to n-hexane prior to GC-ECD analysis [4]. Method 3535A is also a performance based SW-846 method that allows for method modifications. This application note describes an optimized SPE procedure using C18 SPE cartridges to extract target analytes in water samples, and eluting with acetone and n-hexane mixture instead of DCM. After evaporation, the analytes are enriched in n-hexane thus no solvent exchange is needed for GC-ECD detection. In addition, sodium sulfate drying can be eliminated when using the acetone:n-hexane elution solvent. Two distinct layers (hexane on top and water on bottom) are formed after evaporative removal of acetone and partial removal of n-hexane, facilitating the easy transfer of the top n-hexane layer into a graduated glass tube for instrumental analysis or continuing concentration to 1 mL for enhanced sensitivity. This step also helps to improve aldrin recovery which could be adversely lost in the sodium sulfate drying step.
An optimized SPE procedure has been demonstrated for the extraction of EPA method 8081 and 8082 analytes in water. The modified method uses non-chlorinated solvents (acetone and n-hexane) to elute the target analytes and surrogates that are retained on the C18 sorbent. The optimized elution requires no sodium sulfate drying or solvent exchange steps, resulting in a more efficient and cost-effective SPE method for such analysis. Excellent recoveries and RSD% have been achieved even for the noticeably troublesome compound, aldrin, which may get lost in the sodium sulfate drying step or degraded on scratched glass surfaces.