Volatile Organics Sample Collection
This section summarizes the sample collection and handling protocol.
Stainless and glass lined canister are purchased from various vendors for ambient air monitoring. Field samplers consist of electronic flow controllers and stainless steel diaphragm pumps with timers. These samplers push the air into the canister in a controlled flow of 8 cc/min for 24 hours. This pressurizes the samples to 20 to 22 psia. Pressurized samples are stable for longer periods of time. The sample maximum holding time is 30 days.
The cans are vacuum purged and thermally cleaned at 100°C for 8 cycles with humidified nitrogen purge gas . The purge gas is from a liquid nitrogen dewar. Cans are then pumped to a minimum of 100 millitorr before being sealed for shipping to the sites. Cleaned cans are shipped to the field operators by BAQS staff during PM2.5 filter deliveries. EPA cleaning specifications from method TO-14 are used. This means that a batch of cans is considered clean if a can from a cleaned batch has less than 0.2 ppbv of any target compound. If the can has been found to contain more than >2ppbv the whole batch is recleaned.
Sample collection encompasses installing and leak testing the cans in a VOC canister sampler. The can is installed, the can "before sampling" vacuum reading is logged on the field data sheet, and the timer set for the sampling start time. The next work day after sampling, the final pressure is logged and the can is sealed and shipped back to Albany. The field data sheets are logged into an "Access" database program to record the field data and operator comments. This information is used by the chemist to build the automatic analysis file in the Gas Chromatograph/Mass Spectrometer (GC/MS) system.