Chloroprene (C4H5Cl), 2-chloro-1,3-butadiene, has a vapor pressure of 226 mm Hg @ 25 C, a boiling point of 59 C, and a molecular weight of 88.5 g/g-mole. As such, it is classified as a volatile organic compound (VOC).
Being a VOC, one would think that SW-846, Method 0030 would be the ideal choice for capturing chloroprene from stack gases. Indeed, in lecture we identified Method 0030 applicable to those organic compounds with boiling points from 30-100 C, of which chloroprene certainly is a member. However, if you review the paper Larry Johnson and I put together for the Title III HAPs (paper can be found in the Student Workbook), we identified chloroprene as questionable using Method 0030. EPA has data that shows Method 0030 works well in the laboratory under control conditions for capturing chloroprene, but mixed results in the field. It might be that chloroprene breaks through (low breakthrough volume) the Tenax and Tenax/charcoal traps in the Method 0030 sampling train or that oxidants in the stack gas reacts with the captured chloroprene on the resin bed, thus providing a negative bias to our concentration. We really don’t know, but can only speculate.
However, EPA does have data to show that Method 0031 gives good results based upon a Method 301 validation. Remember, Method 0031 uses three adsorbent traps (Tenax, Tenax and Anasorb-747). Anasorb-747 is a carbon molecular sieve adsorbent, with large surface area and very amenable to capturing volatile organics. Also remember that Method 0031 allows the sampling rate to be as low as 0.25 L/min, thus allowing considerable more contact time for the organic with the sorbent resins!
Consequently, the method of choice for quantitating chloroprene from industrial sources is SW-846, Method 0031.
Recently, EPA, Emission Measurement Center, Research Triangle Park, NC has posted on their web site (https://www.epa.gov/ttn/emc/tmethods.html) relevant methods and procedures for emission testing and monitoring. The web site is designed to provide the user guide in the application of stack test methods to specific analytes of interest. The methods are presented under five (5) different categories. The categories are based on a combination of (1) the legal status of the methods with regard to their application under federally enforceable regulations and (2) the validation information available on the method and the Agency’s corresponding confidence in application of the method for its intended use.
Category A: Methods proposed or Promulgated in the FR
These methods are used for compliance purposes under 40CFR 60, 61, and 63 by industrial sources. These methods are being reviewed to meet EPA’s new format as recommended by the Environmrntal Monitoring Management Council (EMMC).
Category B: Source Category Approved Alternative Methods
These methods are approved alternatives to the test methods outlined in 40 CFR 60, 61, and 63. They have been used by sources for determining compliance. The Administrator has issued an official EPA letter stating the validity of the methodology as an alternative to the FRMs
Category C: Conditional Methods
These methods have been evaluated by the Agency and may be applicable to one or more source categories. EPA has reviewed the method QA/QC, applicability to a source category, field and laboratory validation studies etc.
This method may be used by State and local programs in conjunction with Federally enforceable programs (e.g., SIP, Acid Rain, Title V Permits etc.). The source must get approval as alternative before using to meet Federal requirements.
Category D: Preliminary Methods
The performance of these methods is not as well defined as those in the conditional category. May be used in limited application as “gap filling” methods.
Category E: “Idea Box”
Methods concepts to promote information exchange.
Within each category, EPA provides examples of test methods for specific analytes. For more information dealing with the application of source methods to specific analytes, contact Mr. Tom Logan, US Environmental Protection Agency, MD-19, Research Triangle Park, North Carolina, 27711, 919541-2580.
For other applications of SW-846 methods in quantifying your target compounds, please contact Ms. Robin Segall, U.S. Environmental Protection Agency, MD-19, Research Triangle Park, North Carolina, 27711, 919-541-0893.