Analysis of 1,4-Dioxane in Drinking Water with Semi-Automated Solid Phase Extraction (SPE) Using EPA Method 522
Prepared by R. Addink, T. Hall
Toxic Report Laboratories, 580 Pleasant St, Watertown, MA, 02472, United States
Contact Information: firstname.lastname@example.org; 617-393-2396
EPA 522 defines a laboratory protocol for the extraction for analysis of 1,4-dioxane in drinking water. The method uses solid phase extraction paired with GC/MS analysis. The usage of selective ion monitoring (SIM) is often utilized to achieve minimum detection levels.
Due to the relatively high volatility of 1,4-dioxane, the use of a 2 gram coconut charcoal cartridge is required for the retention of 1,4-dioxane from aqueous samples. Cartridges are then eluted with a small portion of dichloromethane, and evaporated to 1 mL. The procedure requires a slow sample loading process where low rates and times must be precise and consistent.
To meet demands for a low-cost method that requires less financial investment than fully automated systems, we developed a simple semi-automated system which is fast, inexpensive and yields high quality data.
Method: Six 500 mL water samples were prepared, acidified till pH~2 and spiked with 1,4 dioxane (25-50ug/L). The bottles were loaded onto the system, rinse bottles filled with 40 mL dichloromethane. 1-2 g coconut charcoal cartridges were put in 6 positions and vacuum turned on. Cartridges were conditioned with 3mL DCM (drain), 3 mL methanol (drain), 3 mL methanol (wet) and 5 x 3 mL water (wet). Samples were loaded across cartridges under vacuum and dried (10 min). Sample bottles were rinsed automatically with nitrogen and DCM rinses loaded. Eluents were collected for analysis into Direct-to-GC Vial Collection Vessels and dried over Na2SO4 cartridges. Samples were reduced in volume using automated concentration and analyzed with low-res GC/MS.
Excellent recoveries of 80-90% were seen for 1,4-dioxane, well within the acceptance windows (70-130%). Total run time is about 90 min including 1 hour of sample loading. The system is inexpensive, producing fast and reliable data. It is a good solution for laboratories that prefer to avoid manual or fully automated methods.