Storage and Preservation of Artificial Sweeteners in Groundwater Samples

Abstract

AbstractCompound‐specific standardized sampling and storage methods are not available for artificial sweeteners found in groundwater. This study aimed to understand: (1) the appropriate length of storage time for samples containing acesulfame (ACE), sucralose (SUC), saccharin (SAC), and cyclamate (CYC) in simulated groundwater (SGW); (2) conditions of their stability; and (3) which sampling materials are appropriate for sample collection. The evaluated storage conditions included acidification, headspace, exposure to light, and refrigeration; the evaluated sampling materials included steel, stainless steel, aluminum, polyvinyl chloride, polyamide (nylon), polypropylene (PharMed BPT™) tubing, styrene‐ethylene‐butylene co‐polymer (MasterFlex™) tubing, and polytetrafluoroethylene (Teflon™) tubing. All compounds evaluated were stable in storage at 4 °C for 241 d (8 months). Concentrations of artificial sweeteners were consistently within 60% to 120% of original concentrations, except ACE and SAC that were substantially lower under acidified conditions at 25 °C after 241 d. Artificial sweetener concentrations remained nearly constant while in contact with all sampling materials except steel. SEM and TEM images showed oxidation of steel occurred; moreover, removal of all artificial sweetener compounds from aqueous solution had occurred after 289 d. These results suggest artificial sweetener analyses conducted within 14 d of sample collection produce optimal results; however, longer storage times may be acceptable under certain conditions. The results also suggest concentrations of artificial sweeteners in SGW are not affected by contact with typical well casing, sampling, and storage materials, with the exception of steel. The findings from this study will improve the use of artificial sweeteners as tracers in environmental studies.