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This document is republished with the permission of Gossman Consulting Inc.

GLOSSARY OF TECHNICAL TERMS


2,3,7,8-tetrachlorodibenzo-p-dioxin  This compound is considered the most toxic of the chemical family of dioxins and furans.  It is assigned the toxicity equivalent factor (TEF) of "1", and all other dioxins and furans are assigned a TEF value less than "1".

Adsorb  To collect (a gas, etc.) in condensed form on a surface.

Aliquot  An analytical chemistry term referring to a measured portion taken from a solution.   When an aliquot of a sample solution is analyzed, the concentration of the targeted compound in the original solution can be calculated from those analysis results.

Analyte  The targeted compound or element for which an analysis is being executed.

Background noise  Electrical or chemical interferences with the signal coming from the detector of an analytical instrument.  The analyte must create a signal in the detector which sufficiently overcomes these interferences in order to be detected.  In the case of dioxin/furan analysis, the signal to noise ratio must be greater than 2.5 for all monitored analyte signals.

Blank  A quality assurance sample which is analyzed to ensure that any contamination is known and can be accounted for.  Contamination may occur before, during or after the sampling or analysis testing procedures.  The primary contamination of concern is the analyte or analytes that are being tested for.  In dioxin/furan testing, the method calls for a field blank because of the several different solutions and pieces of equipment used in the testing.  As an example, a basic set of blanks normally analyzed in dioxin testing is the method blank, field blank and trip blank.

Calibration  Procedures that are prescribed by the dioxin/furan test methods to check the performance of the analytical instrumentation.  The procedures involve the running of standards at different concentrations and ensuring that the results are consistent with the predicted concentration value.

CFR  Code of Federal Regulations.

Congener  A generic name for one particular compound of the same chemical family; e.g. 2,3,7,8, tetrachlorodibenzo-p-dioxin is one congener of the 75 chlorinated dibenzo-p-dioxin congeners.

 
Daily performance checks  A routine testing of the electronic lab equipment to confirm that the machines are properly calibrated and accurate.  These are performed at routine times each day and are recorded as part of the Quality Assurance/Quality Control (QA/QC) data for that equipment.

Detection limit  A calculated value, the level at which a particular piece of analytical instrument can detect the presence of a specific compound above the background noise of the instrument detector.  For dioxin/furan analysis, this value is determined by the signal to noise ratio which must be a minimum of 2.5.
 
Dry standard cubic feet (dscf)  See dry standard cubic meters.  The only difference between the two terms is the use of English units of measure rather than metric.

Dry standard cubic meters (dscm)  Concentration of contaminants in gases emitted from sources (such as cement kilns) are generally expressed as a weight of that material per a volume of gas.  Emissions from sources often contain water vapor from evaporation of water in the processed material or as water from combustion of hydrocarbons.  This amount varies from source to source and at variable temperatures from source to source.  To make an emission rate meaningful for comparison to another source or to a permit limit, the emission rate must be stated as a weight per (dry) gas at standard conditions.  The specific standard conditions are set by the applicable authority, often a national laboratory group.

Duplicate analyses  The sample is split and then each split is subjected to analysis.

Filter support  A housing that holds the flimsy glass fiber filter in place in the sampling train.

Fractionated  The second main step in the analysis of a dioxin/furan field sample.  After the field sample has gone through extraction procedures, the dioxin/furans, if there are any, are put into a solution.   The solution must be cleaned up and fractionated.  This step is a series of procedures where the solution is passed through different columns of packed chemical material to purify the solution prior to injecting it into the analytical instrument.

Gas chromatograph/mass spectrometer (GC/MS)  A gas chromatograph is an instrument where the sample gas passes through a carefully heated coiled metal, glass or silica tubing packed with a specially prepared media, or a glass or silica coil of a very precise bore measurement with an internal coating which causes the different compounds in the gas to separate based on their transport properties.  Each compound exits the coil in a known sequence and at a predictable time.  This permits identification of the compounds in the sample through the use of some type of detector at the exit of the coil.  The mass spectrometer is the detector that measures each of these compounds as they leave the coil.  This is the most accurate device for identifying and determining the concentration of different organic compounds.

Glass fiber filter  A special type of filter used in the Method 23 stack sampling train.  It will not react to chlorinated hydrocarbons as some other mineral fiber or paper filter may.

High resolution gas chromatography (HRGC)  A gas chromatograph especially configured to detect very low concentrations of hydrocarbon.  The HRGC must be equipped with temperature programming, a high resolution capillary column for the separation, as well as other required accessories such as syringes, high purity gases and a data system to control operations, collect and process data.  For dioxin/furan analysis of samples.

High resolution mass spectrometry (HRMS)  A mass spectrometer  which can identify a hydrocarbon by its very specific ion mass.  The unit must be able to resolve each ion mass peak from another with a minimum of 10% difference between each mass peak.  It also must have a data system to control and monitor the multiple ion monitoring process.  The data system must also be able to acquire data at a minimum of ten ions in a single scan and be able to provide other details of the mass spectra for each hydrocarbon.  For dioxin/furan analysis, the HRMS must be closely coupled with a HRGC to separate the individual hydrocarbons (dioxin or furan) before they enter the HRMS.

Homologous group  All of the dioxins (or furans) of the same base grouping designated by the number of chlorine molecules in the compound.  For example, all tetrachlorodibenzo-p-dioxins (TCDD) have four chlorine molecules and are a homologous group.  2,3,7,8-TCDD has four chlorine molecules, one each at the 2, 3, 7 and 8 positions, and is thus one member of the tetra group.

Impingers  A glass tube containing a fluid that is part of a sample train.  Gas from the source is passed through a dip leg (bend in the tubing) and then bubbles up through this fluid.  The fluid may be water or a chemical that reacts with some constituent in the gas.  The gas analytes of interest then remain in the fluid for subsequent analysis.

Initial instrument calibration  The first calibration of an instrument, usually intended to achieve a gross, or rough, calibration that will be subsequently refined for accuracy.

Interferences  Any substance or mechanism that compromises the accuracy of an analysis of another substance.  Sample preparations and analyses must often be performed in certain steps to remove substances that would reduce the accuracy in determining the concentration of another substance.

Internal standards  These are standards which are added to the sample to be analyzed prior to it being analyzed.  For dioxin/furan analysis, they may be the same compounds as the analytes of interest, very similar or radioactively labeled.  They are added to the sample in a quantitatively known manner.  They are then analyzed for, just as are the analytes of interest.  Results allow the analyst to be more precise in determining the concentration of the unknown analytes.  Also, the results can indicate whether any portion of the sample was lost during the many steps of the analysis, therefore effecting the accuracy of the results.

Isokinetically  A term which pertains to the sampling of stack gas.  It means taking the sample under specific and relatively constant physical conditions such as gas flow rates, velocity, pressures, etc.  The sampling of a stack requires several hours, movement of the sampling train between sample points on the stack and obtaining the required amount of gas sample.  In order to extract a truly representative sample from a stack the sample must be withdrawn within 10% of isokinetic conditions.  The sample probe nozzle is a key in achieving these monitored conditions.  It should be selected and pre-tested to ensure its ability to maintain the isokinetic conditions while sampling gases moving through the stack.

Isomer  In this case, one specific arrangement of chlorine molecules in a homologous group, e.g. 2,3,7,8-TCDD is one isomer of the TCDD group.  2,4,7,8-TCDD would be another isomer of the same group.

Kg  Kilogram, or  1000 grams.

Matrix spikes  A quality control sample prepared and run during the analysis of the sample.  It is prepared using the same media and chemical the field sample was taken in.  It is split into two samples and spiked with internal standards.  The two samples are then analyzed through the same steps as the field sample.  The results are compared and for dioxin/furan testing should agree within 20% of each other.

mg  Milligrams, or 0.001 grams.

ng  Nanogram,  or 0.000000001 grams.

ng/dscm   Nanograms per dry standard cubic meter.  See dry standard cubic meter.

Nozzle  The tip of the sample probe inserted into the stack to sample the stack gas.  These nozzles come in a number of opening sizes corresponding to the flow rate needed for the sampling period.

Packed column  The metal or glass coil that has the precisely ground specially prepared media in it that the gas chromatograph carrier gas flows through.  The sample when injected into the carrier gas, flows through the media which separates compounds in the sample.  See also gas chromatograph/mass spectrometer (GC/MS). 

Products of Incomplete Combustion (PICs)  Hazardous organic compound emissions which, in theory, result in complete combustion of fuels or other materials.  Burning hydrocarbons breaks them down from more complex into more simple compounds.  Burning that is not hot enough or long enough will result in some intermediately complex hydrocarbons.  These intermediately complex hydrocarbons also routinely occur in nature for a wide variety of reasons.  The EPA assumes that hydrocarbons volatized out of the raw feed in a cement kiln (or lime kiln, or aggregate kiln) comes only from incomplete combustion.

Quality Assurance/Quality Control (QA/QC)  A set of procedures to ensure that analyses have been performed accurately.  Some of these procedures precede the analysis and some follow the analysis.

Quantitation Limit  A limit above the detection limit which, through calculation, meets certain statistical confidence criteria as defined by the test method, e.g. the confidence level for dioxin/furan analysis is 99%.  The lowest possible level is also called the minimum quantitation limit (MQL).

Relative response factor  This is a value calculated for each analyte of interest from calibration response factor data.  These values are then used to determine the concentration of those analytes in the analysis of the test sample.  This determination is made by comparing the responses of the known analytes to the responses of the unknown analytes.

Resin absorbent sampling cartridge  This is a glass vial with a specially prepared resin that adsorbs organics out of the sample gas.

Response factor data  This data is obtained during analytical instrument calibration procedures.  In dioxin/furan testing, the data comes from analyzing a series of standards with the GC/MS and recording the detector response to the known concentration of the individual analytes in each standard.  Calculations are then made using the detector response data and the known concentration of each analyte in the standard to determine the relative response factor.

Rinsate  A solution used to wash across the inner surface of sampling equipment to ensure that all of the sample being analyzed will have all of the analyte.

Sample catch  The actual amount of sample that the sampling equipment contains at the end of the sampling period.

Sample matrix  The type of media (broadly; solid, liquid, or gas) that the analytes are found in, sampled in, or extracted to.  For example, a stack gas may be sampled in the gas phase by a bag or passed on to a sample train and captured in solid or liquid media.  Within each of the broad categories there can be many more types of media or matrix.  In dioxin/furan testing, quality control samples using the sample matrix must be tested to determine if they have an effect on the analysis results.

Sample probe  The tubing (generally glass) that is inserted into the gas stream to extract a sample of the stream.

Sample recovery operations  The activity to properly transfer the sample out of the sampling device into containers.  This includes measurement of the fluids, rinsing and measurement of the rinsate, the addition of preservatives or reactants, etc.

Sample train breakdown  The first steps in sample recovery.  It involves very careful disassembly, rinsing and collection of sampling apparatus components and materials.  For dioxin/furan testing, specific procedural steps are specified by the test method for all of these activities.

Sample transfer lines  The tubing connecting different filters, impingers, etc. in a sample train through which the sample gas flows.

Sealing greases  Greases used to create gas-tight connections between glass to glass connections or Teflon to glass connections.  The test method for dioxin/furan emissions requires that no greases be used to prevent contamination of the sample.

Spike  The addition of a compound of known composition and concentration to a material prior to analysis.

Standard  See internal standards.

Surrogate compounds  A substituted compound.  When a compound is very hazardous or difficult to work with, it may be desirable to use a less hazardous material which has similar properties.  A surrogate compound should be approved before it is used.  In dioxin/furan testing a group of surrogate compounds are used as a part of the internal standards.  The method specifies when and where these should be used.

Toluene QA rinse  A quality control sample collected when testing stack gases for dioxin/furan emissions using method 23.  After the stack sampling equipment has been cleaned and rinsed with acetone and methylene chloride as per the method, a final rinse is made with toluene.  This rinse may be kept separate from the other cleaning rinses.  If it is analyzed separately for dioxin/furan it can demonstrate that the prior cleaning and rinsing were effective in removing all the dioxin/furan from the sampling equipment.  This rinse may be added to the other rinses and become part of that analysis.

Toxic Equivalent Quantity (TEQ)  The quantity of each PCDD/PCDF emitted multiplied by its TEF.  In this manner, devices that emit different relative quantities of the different PCDD/PCDF compounds can be compared to  a standard limit.

Toxicity Equivalency Factor (TEF)  An assignment of relative toxicity with 2,3,7,8-TCDD being "1".

μg  Micrograms, or 0.000001 grams.