Solid phase extraction (SPE) in US EPA Method 625.1, the performance of smaller samples

Environmental methods for water analysis often specify sampling 1 L of water to provide the sensitivity needed for determination of contaminants at low concentrations for health monitoring. In the past decade sensitivity of the analytical technique (GC/MS) has improved and with split/splitless introduction and large volume injection options a wide range of concentrations can be effectively measured. Coupled with reduced concern about sample homogeneity and flexibility in sample size for automated samplers, the possibility of smaller samples bears investigation. Other benefits of smaller samples include reduced shipping costs and they are easier to handle and store than large bottles. Less solvent is needed for extraction and therefore less will be evaporated when the sample extract is reduced. If solid phase extraction is used, rather than liquid-liquid, the solvent used may be further reduced. In this application note, Biotage examines the results for a dramatically reduced sample size of 100 mL in EPA Method 625.1. Several different matrices are examined, including reagent water, synthetic wastewater, and an acetic acid mixture used in the toxicity characteristic leaching procedure. Samples are spiked with a test mixture to determine recoveries of varying unknown concentrations.