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

Oral Presentation

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


Contact Information: ruudaddink@toxicreports.com; 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.