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
                                      Capture Detectors


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.


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 times.