Lowering Detection Limits for 1,4-Dioxane in Drinking Water Using Large Volume Injection in an Unmodied Splitless GC Inlet

Global concern over the carcinogenic potential of 1,4-dioxane, along with its identi cation as a Group 2B compound by the World Health Organization’s International Agency for Research on Cancer (IARC), has led to increased regulatory interest in this compound. For example, as part of Unregulated Contaminant Monitoring Rule 3 (UCMR3), the U.S. EPA is requiring increased monitoring of 1,4-dioxane in drinking water and has revised the 1x10-6 cancer risk assessment level down to 0.35 μg/L. This risk assessment level corresponds to the lifetime probability of one individual in an exposed population of one million developing cancer, and it is the basis for the UCMR3 proposed minimum reporting level (MRL) for 1,4-dioxane of 0.07 μg/L [1]. Concurrent solvent recondensation–large volume splitless injection (CSR-LVSI), a technique described by Magni and Porzano [2,3], can be advantageous when trying to analyze trace-level contaminants, such as 1,4-dioxane, in clean matrices like drinking water. Since more target compound is introduced onto the analytical column, detectability is improved; however, a specialized injection port, such as a PTV, is generally required [4]. Using a PTV inlet is not an option for analyzing 1,4-dioxane in drinking water, because this technique requires a difference in boiling point temperature (Tboil) between the solvent and solute of over 100 °C, in order to prevent loss of target analytes to the split vent when performing solvent removal [5]. In this case, the temperature difference is not adequate, as dichloromethane (Tboil = 40 °C) is the SPE elution solvent and 1,4-dioxane (Tboil = 101 °C) is the primary solute of interest. Building on work by chemists at Thermo Scienti c, who have successfully applied their CSR-LVSI technique to drugs-of-abuse, pesticides, and polychlorinated biphenyls [6,7,8], our lab has been exploring the use of CSR-LVSI with a completely unmodi ed Agilentstyle splitless GC inlet. Given how close the boiling points of the compounds in question are to the cartridge elution solvent, we theorized our CSR-LVSI approach would be especially applicable for analyzing 1,4-dioxane in drinking water according to U.S. EPA Method 522. We used a fast autosampler injection with liquid sample band formation in a liner containing glass wool, a retention gap presstted to the analytical column, and a starting GC oven temperature below the boiling point of the solvent. Previously, we had successfully analyzed a variety of compounds, including polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH), EPA Method 8270 semivolatiles [9], brominated ame retardants [10], as well as many organochlorine, organonitrogen, and organophosphorus pesticides using this technique. Here we assess its potential to lower detection limits for 1,4-dioxane in drinking water.