Healthy Indoors Magazine - USA Edition

Healthy Indoors | 33 molecular weight and extremely volatile compounds, such as propane and the freons, just to name a few. The solvent desorption method, utilized in many NIOSH methods, dilute out the toxic compounds with a solvent thereby preventing low detection levels. Either you thermally decompose your analytes, or you dilute them out. Either choice has major drawbacks that can affect your data. TO-15 collection and analysis afford the best approach to the isolation and identification of your problem toxic vola- tile organic compounds. Your odor-causing compound may not be detected with other techniques. TO-15 Sampling Considerations There are several choices when considering your next TO- 15 sampling event. There are several sizes of sampling canisters available for sample collection. Your analytical laboratory can provide 6 liter and 400 ml mini cans, which are among the most popular sizes. The 6-liter canister af- fords the best detection limit possible due to the introduc- tion of a 500-ml sample size. The 6-liter canister is recom- mended for regulatory compliance projects and for those projects where no perceptible odor is detected. The 400-ml mini can is an excellent choice because of its compact size and ease of use. Use this smaller canister when the identi- ty and concentration of a noticeable odor is needed. Next, you must choose the sampling regulator. Regula- tors control the flow of air into the canister and range from 5-minute grab samples to as long as 24 hours. The sam- pling canister size can limit your sampling interval choices. Ask your laboratory about the available choices. There are two different types of TO-15 canisters. You can use passivated or non-passivated canisters. The best choice is to ask your laboratory for passivated canisters. These canisters can have trade names such as Silcosteelä, Sulfinertä, etc. The passivated canisters contain an inter- nal coating of glass and/or other inerting agents that are only several molecules in thickness. The coating is bound to the metal and is not subject to breakage or chipping with rough handling. This coating increases the inertness of the canisters allowing better detection of difficult compounds (e.g. sulfur and polar compounds). Non-passivated canis- ters do not have this coating on the inside. The TO-15 canisters and regulators are very expensive and should be handled with the utmost care. Many labs provide a free loaner service provided you return the equip- ment for analysis within a week or so. Keep in mind that the canister was certified as clean prior to your receipt. If you return the canister to the laboratory without taking a sam- ple, you may still be responsible for the cost of cleaning and certification. Check with your individual laboratory for Organic Compound' methods in ambient air. These meth- ods are more commonly referred to as the 'TO' methods. The first useful pair of methods was TO-1 and TO-2 where organic compounds were collected on sorbent traps and introduced into a specially designed cryogenic focus- ing interface connected to a GC/MS (gas chromatograph/ mass spectrometer). This was the method of choice for the EPA for the determination of organic compounds in am- bient air at Superfund sites and other toxic sites. To use TO-1/TO-2, the investigator needed to use an air pump to draw large volumes of air across these sorbent traps. The pumps needed to be calibrated and added to the complex- ity of the sampling event. Within a few years, TO-14 began to replace TO-1/TO-2 as the method of choice. The main difference to the sam- pling method employed with TO-1/TO-2 was that a stain- less-steel vessel, resembling a basketball with a metal frame and valve, was used to collect the sample. The ves- sel, also known as a 'SUMMA Canister,' was cleaned and evacuated in the laboratory. The SUMMA canister was then sent to the field where the investigator simply opened the valve. The sampling event would begin and end without the use of calibrated pumps or complicated collection media. More recently, a new flavor of TO-14 has emerged as TO-15. TO-15 uses more sophisticated canister technolo- gy. The analytical equipment today is capable of detecting parts per trillion of certain volatile organic compounds. The GC/MS instrument also makes it possible to look at 'un- known compounds' and make tentative identifications. It is this versatility that makes TO-15 one of the most powerful tools that an investigator can use for any initial evaluation. Advantages of TO-15 TO-15 stands out from other sampling and analysis meth- ods. The sampling protocol is very easy to perform while producing more reliable data than most methods. TO-15 can be used for a wide range of compound types. Some important toxic volatile organic compounds are best han- dled by the TO-15 whole air approach. Alternative approaches to whole air analysis in can- isters are the thermal desorption and solvent desorption methods. Some compounds aren't easily desorbed (re- moved) after adsorbing (sticking) onto the sorbent media, such as the collection methods outlined in TO-1/TO-2 and most NIOSH methods. In the thermal desorption approach, the chemist inserts the collection tube into a specially de- signed GC/MS interface, and heats the tube to drive the toxic compounds into the GC/MS instrument. Losses can occur if the compounds are thermally unstable and decom- pose during heating. Other losses can be seen with low

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