Air Toxics Sample Analysis

Once sampling is complete, the canisters are collected and brought to IDEM's Air Toxic Monitoring Laboratory for analysis. All canisters samples are logged in a laboratory notebook. The log entry includes the sample location, sample date, canister number, and sample pressure in the canister.

In the past 20 years, the instrumentation used for the sampling and analysis of air toxics has become much more sophisticated and much more accurate at measuring the levels of pollutants in the air. IDEM continually strives to optimize its instrumentation and methodology to provide the most accurate data possible.

The canister samples are analyzed using gas chromatography/mass spectroscopy (GC/MS). The GC/MS system is calibrated to measure concentrations of 63 target organic compounds. Eight levels of standard ranging from 0.5 ppb (parts per billion) up to 10.0 ppb are used for the calibration. The calibration curves are verified to be within 30 percent of linear. The samples are analyzed using the same method used to analyze the standards, and concentrations of toxic compounds are reported.

Once the sample analysis is complete, the data are quality assured and entered into the ToxWatch database.

Tour of IDEM's Air Toxics Laboratory

IDEM maintains its own air toxics laboratory. In this laboratory IDEM chemists are able to analyze samples of multiple toxic air pollutants. Below is a tour of the portion of the lab responsible for analyzing the ToxWatch pollutants.

The view as you enter IDEM's Air Toxics Laboratory.

A workstation used by IDEM's laboratory chemists to analyze air toxics samples. The instrument on the left is a GC/MS (gas chromatograph/mass spectrometer) system.

A close up of IDEM's newest GC/MS.

The inside of the GC/MS is heavily insulated because the GC/MS can heat up to several hundred degrees while conducting a sample analysis. The ring in the middle is called a capillary column. It is made from a special kind of glass called fused silica. It is a very long tube (almost 200 feet long) with very small diameter (0.32 mm, about the size of a single grain of salt). The sample is fed through the column to help separate the individual pollutants within the sample so they can be analyzed. The individual pollutant is identified by their retention time (the time it takes for them to travel all the way through the column), which is based on their molecular weight, boiling point, and polarity.

A closer shot of the inside of the GC/MS system shown in the previous picture.

The instrument in the center is a GC/FID (gas chromatograph/flame ionization detector) system. It measures the TNMOC (total non-methane organic compounds) of the sample. This gives the chemists an idea of how much total pollutant there is in the sample. This is important to know because if there is too much total pollutant in a sample it can damage the GC/MS system. If the GC/FID detects a high concentration of pollutants in the sample the chemists can dilute the sample (add extra clean air) so it doesn't damage the GC/MS. After the sample is analyzed they then multiply the results by the dilution factor (based on the amount of air added) to determine the actual concentration in the original sample.

This is an auto sampler interfaced with the GC/MS system for VOC analysis. The auto sampler has capacity to connect sixteen canister samples in a batch. Each sample analysis takes over an hour to run. The auto sampler is programmed to automatically feed the next sample to the GC/MS system to be analyzed.

This is an absolute pressure gauge. It is used to measure canister pressure very accurately. The system is part of the canister clean up assembly and measures the canister pressure after sampling to establish the consistency of the monitoring program.

This is a canister clean up assembly. The oven is used to heat the canisters to 90oC during the cleaning cycle. After they are cleaned, the batch is certified clean and all canisters are evacuated to be used for the next sampling event.

A rack of clean, evacuated Summa canisters ready to be used for the next sampling date.

Additional shot of the auto samplers and a liquid nitrogen tank. Liquid nitrogen is used as a cryogen (refrigerant) for the auto samplers.

Inside IDEM's other GC/MS system. This system is used for duplicate analysis as part of the quality control process. It also acts as a backup system for the main GC/MS system.