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Method 18 Engineering

Measurement of Gaseous Organic Compound Emissions by Gas Chromatography


This method is designed to measure gaseous organics emitted from an industrial source.  Samples are collected using a Tedlar bag, adsorbent tube, or by a direct interface and analyzed by GC with an appropriate detector which is typically an FID (flame ionization detector).  The method should not be used for compounds that  (1) are polymeric (high molecular weight), (2) can polymerize before analysis, or (3) have very low vapor pressures at stack or instrument conditions. 

This method as written when used for compliance samples has very strict procedures concerning sample collection, analysis, and associated quality control requirements.  However, this method is very popular for use with purposes other than compliance testing.  Many of the requirements involving triplicate injections and spiked sample analyses will not be performed at the client's request to lessen the analytical costs when the data are for internal or engineering process purposes. As such, many of the stricter requirements will be discussed in greater detail in Method 18 Compliance.

Tedlar bag samples are collected using a lung system or vacuum box to draw a dry sample into the bag.  In this sampling technique, the sample gas never passes through the sampling pump used to draw the vacuum.  Moisture in the stack gas should be removed before the sample enters the bag.  Tedlar bags are appropriate for non-reactive compounds and compounds that will not adhere to the surface of the bag (not alcohols or amines).  Bags should never be filled more than 50% full if they will be transported to the laboratory for analysis via air courier to allow room for the contents of the bag to expand and not burst during transit. 

Adsorbent tubes are collected using a sampling train consisting of a probe, sampling pump and midget impinger located prior to the adsorbent tube to remove the moisture in the stack gas.  This midget impinger is not needed if the moisture levels are not expected to exceed 2-3%.  The adsorbent tube should be in a vertical position in the sampling train to prevent channeling.  The type of adsorbent tube used for sampling should be selected based upon its performance in collecting the analytes of interest.  There are numerous resources (NIOSH, OSHA, tube manufacturer's) to consult for tube selection.  The method requires a check for breakthrough, if thought to be a problem,  which means the front and back half portions of the adsorbent tube must be analyzed separately.  The breakthrough requirement is that an analyte should not be found on the back half at a level greater than 10% of the total on the tube.

The method does not specify any holding time from collection to analysis, however, it is recommended to analyze the samples as soon as possible especially if collection is in a Tedlar bag.

The compounds listed below comprise a list of analytes that can be determined following the collection and analysis procedures noted in this method.  There are a vast number of compounds that can be determined using this method.  If you are interested in a particular analyte and do not see it listed below, please inquire as to the applicability of determining that analyte using this method.


(EPA 40CFR Part 60 Appendix A)

Method Data
Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   None specified in method, however, it is recommended to analyzed samples as soon as possible after collection.
Preservatives:   None specified in method, however, it is recommended to keep adsorbent tubes at 4C.
Required Preps:   Tedlar bag, adsorption tubes
Collection Method:   Sampling train for bags, adsorbent tubes or direct injection following Method 18 procedures.
Analytical Methodology:   GC/FID or other suitable detector
Documentation:   18 Engineering


Products You Might Need
SKU Item Price
M18 EPA Method 18 Bag Sampler $ Call for Price
TB Sampling Bags: Air Sampling Bags $ Call for Price


Analyte List*
Analyte
Formula
CAS Number
Detection Limit
Ethylbenzene
C8H10
100-41-4
1
 ppm
Styrene
C8H8
100-42-5
1
 ppm
cis-1,3-Dichloropropene
C3H4Cl2
10061-01-5
1
 ppm
trans-1,3-Dichloropropene
C3H4Cl2
10061-02-6
1
 ppm
p-Xylene
C8H10
106-42-3
1
 ppm
1,2-Dichloroethane
C2H4Cl2
107-06-2
1
 ppm
Vinyl Acetate
C4H6O2
108-05-4
1
 ppm
Methyl isobutyl ketone (MIBK)
C6H12O
108-10-1
1
 ppm
m-Xylene
C8H10
108-38-3
1
 ppm
Toluene
C7H8
108-88-3
1
 ppm
Chlorobenzene
C6H5Cl
108-90-7
1
 ppm
Chlorodibromomethane
CHBr2Cl
124-48-1
1
 ppm
Tetrachloroethene
C2Cl4
127-18-4
1
 ppm
cis-1,2-Dichloroethene
C2H2Cl2
156-59-2
1
 ppm
trans-1,2-Dichloroethene
C2H2Cl2
156-60-5
1
 ppm
Carbon tetrachloride
CCl4
56-23-5
1
 ppm
Methyl butyl ketone (2-Hexanone)
C6H12O
591-78-6
1
 ppm
Acetone
C3H6O
67-64-1
1
 ppm
Chloroform
CHCl3
67-66-3
1
 ppm
Benzene
C6H6
71-43-2
1
 ppm
1,1,1-Trichloroethane
C2H3Cl3
71-55-6
1
 ppm
Bromomethane
CH3Br
74-83-9
1
 ppm
Chloromethane (Methyl chloride)
CH3Cl
74-87-3
1
 ppm
Chloroethane
C2H5Cl
75-00-3
1
 ppm
Vinyl chloride
C2H3Cl
75-01-4
1
 ppm
Methylene chloride
CH2Cl2
75-09-2
1
 ppm
Carbon disulfide
CS2
75-15-0
1
 ppm
Bromoform
CHBr3
75-25-2
1
 ppm
Bromodichloromethane
CHBrCl2
75-27-4
1
 ppm
1,1-Dichloroethane
C2H4Cl2
75-34-3
1
 ppm
1,1-Dichloroethene
C2H2Cl2
75-35-4
1
 ppm
Trichlorofluoromethane
CCl3F
75-69-4
1
 ppm
1,2-Dichloropropane
C3H6Cl2
78-87-5
1
 ppm
Methyl ethyl ketone (2-Butanone)
C4H8O
78-93-3
1
 ppm
1,1,2-Trichloroethane
C2H3Cl3
79-00-5
1
 ppm
Trichloroethene
C2HCl3
79-01-6
1
 ppm
1,1,2,2-Tetrachloroethane
C2H2Cl4
79-34-5
1
 ppm
o-Xylene
C8H10
95-47-6
1
 ppm

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.