S.O.P. No. MLD 052 - Determination of Volatile Aromatic and Halogenated
Compounds in Ambient Air by Capillary Column Gas
Chromatography with Photoionization and Electron
This document describes the sampling and analysis procedure for volatile aromatics and halogens in ambient air. This method was developed by the Northern Laboratory Branch (NLB), Organics Laboratory Section staff and replaces S.O.P. MLD 012 and MLD 042. These methods are modified versions of the U.S. EPA Compendium Method TO-14.
SUMMARY OF METHOD
Ambient air is collected in a SUMMA passivated stainless steel canister using a XonTech 910A sampler. The sampling procedure for Toxics samples is detailed in the Quality Assurance Manual, Volume II, Appendix Q. All the operational procedures and sampling conditions are documented. A record of this information is sent back to the Organics Laboratory along with the sample for immediate analysis. The sample is checked for leakage (integrity of the canister pressure is validated by calibrated gauge reading), documented, and analyzed according to the chain of custody within the laboratory.
A 150 cc ambient air sample is introduced into the system from the pressurized
canister through 1/16" stainless steel tubing with the aid of a mass flow
controller and a vacuum system. A digital flow meter readout, attached
to the GC, provides a visual indication of the proper sample flow during
sampling. Automatic sampling of up to 16 sample containers can be accompanied
with a multi-position automated sampler which is controlled by the GC or
PC (with Star Workstation software). The sample passes through the Nafion
dryer to remove moisture (H20 vapor) from gas streams and is
trapped within empty nickel tubing (150 uL) at -130oC.
The desired components are immobilized (solidified) while oxygen, carbon
monoxide and methane pass through the vent. The injector or trap is purged
with N2 followed by sample heating and injection. The trap is
isolated and heated to 130oC at the rate of 300oC/min.
followed by direct injection of the sample onto the DB-VRX capillary column
(75 m x 04.5 mm I.D., with 2.54 um film thickness). After a 2.0-minute
hold at 130oC, the trap temperature is raised to a final temperature
of 190oC, allowing the higher boiling-point compounds to completely
volatilize and be introduced into the column before the subsequent purge
of the trap with N2 through the vent for the duration of the
analytical sample run. The sample mixture is separated into individual
components by the selectivity of the column and oven-temperature program.
The components eluting from the column are detected by the Photoionization
Detector (PID) and the Electron Capture Detector (ECD) which are set in
a series. The components are subsequently identified and quantified. The
qualitative information on volatile compounds are based upon relative retention