AWWA WQTC57009

1,4-dioxane is commonly found in treated wastewater effluent and landfill leachate due to the extensive use of 1,4-dioxane as a stabilizer for chlorinated solvents such as 1,1,1-trichloroethane (TCA) and a contaminant in some surfactant compounds used in herbicides. Also a variety of personal care products such as shampoo, liquid soaps, sunscreens, moisturing lotions, baby lotions, and hair lotions contained 1,4-dioxane with levels ranging from 3 to 100 parts per million. As more occurrences and distributions of 1,4-dioxane were reported in several states including California, the interest in a reliable and fast analytical method to detect sub ppb levels 1,4-dioxane has increased. Recently, 1,4-dioxane, which the US Environmental Protection Agency (USEPA) classifies as a B2 probable human carcinogen, has been detected in the specific ground and surface waters. The findings of 1,4-dioxane in the water systems prompted the need of extensive monitoring of the compound in the drinking water. But the currently available methods have high detection limits of 10 to 50 ug/L. The high reportable detection limits are the results of poor extraction efficiency and volatile nature of the compound. The Orange County Water District (OCWD) Laboratory has reviewed currently available isotope dilution methods and purge-trap techniques using the GC/MS. Most laboratories are applying the isotope dilution method, but the isotope dilution method involves labor-intensive liquid-liquid extraction and 100-200 ml of methylene chloride for each sample. Due to the poor purging efficiency and infinite water solubility of 1,4-dioxane, the detection limit of purge-trap techniques is 100 times higher than the other purgeable compounds with USEPA method 524.2. The OCWD lab has initiated a series of modifications for the purge-trap extraction and instrumentation of USEPA method 524.2 to improve the sensitivity and reproducibility for the determination of 1,4-dioxane in water. To improve purging efficiency, the purge time has been increased to 20 minutes from 11 minutes instead of increasing the purge flow of 40 ml/minute to prevent foaming of the heavy matrix samples. Also a different type of trap, which contains more carbopack(TM), could improve the response and the shape of 1,4-dioxane peak. For the instrumentation, the GC/MS/MS has been applied to retrieve the ions from GC/MS, which removed the background ions to help the identification of low ppb levels of 1,4-dioxane from wastewater samples. The improved method generated the method detection limit of 0.2 ppb and very reproducible data without manual labor and using only 25 ml of sample compared to the 1000 ml-sample extraction of the isotope dilution method. The split test between purge-trap and isotope dilution method showed the excellent correlation for drinking water and wastewater samples. The improved purge-trap and GC/MS/MS techniques will be very resourceful in saving labor and 100% solvent less extraction with fast turn-around time, high precision, and comparable sensitivity to the isotope dilution method. Includes 6 references, tables.

Product Details

Edition:

Vol. - No.

Published:

11/01/2002

Number of Pages:

14

File Size:

1 file , 260 KB