Analysis of Semi-Volatile Organics in Drinking Water with Semi-Automated Solid Phase Extraction Using EPA Method 525.3

Topics in Drinking Water
Oral Presentation

Presented by T. Hall
Prepared by R. Addink
Toxic Report Laboratories, 580 Pleasant St, Watertown, MA, 02472, United States


Contact Information: [email protected]; 617-393-1713


ABSTRACT

United States EPA Method 525.3 outlines the procedure for the extraction and analysis of a wide range of semi-volatile organic compounds in water. The method allows for use of Solid Phase Extraction (SPE) of water samples. It incorporates a set of QC and acceptance criteria requiring precise and reproducible analytical practices.

To meet demands for a lower cost method that requires less financial investment than automated systems, we developed a simple semi - automated system which is faster and cheaper while yielding high quality data.

Six 1 L water samples were acidified to pH ~2, spiked with 5-10 mL methanol and with 525.3 standards. The sample bottles were attached to the SPE system and sample rinse bottles were filled with 25 mLs dichloromethane. C-18 cartridges were installed in each of the six positions.

The next steps were divided in two stages. Stage 1: cartridges conditioned under vacuum with dichloromethane, methanol and water (5 mLs each), followed by loading the cartridges, drying (nitrogen) and automated sample bottle rinse (dichloromethane). Stage 2: bottle rinses eluted across the C-18 and Na2SO4 cartridges and the eluent collected for analysis.

Collection tubes with Direct-to-Vial connections were put in an automated concentrator, pre-heated for 15 minutes at 50 C, and heated in sensor mode under 7-10 psi nitrogen which assured automatic shut-off at 1 mL. They were further reduced in volume further in a vial evaporator and spiked with recovery standards. Analysis was done with low res GC/MS.

Very good recoveries were seen for the various compound classes in the method (e.g., organochlorine pesticides, PAHs) between 90-120%. Total run time is about 90 min including 1 hour of sample loading. The system is cheap and produces fast and reliable data. It is a good solution for laboratories that prefer to avoid manual or fully automated methods.