1、Designation: D7203 11Standard Practice forScreening Trichloroethylene (TCE)-Contaminated MediaUsing a Heated Diode Sensor1This standard is issued under the fixed designation D7203; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes procedures for screening mediaknown to contain the halogenated volatile organic comp
3、ound(HVOC), trichloroethylene (TCE). Procedure A is to be usedfor screening soil known to contain TCE and Procedure B is tobe used for screening water known to contain TCE.1.1.1 Both Procedures A and B involve measuring the TCEconcentration in the headspace above a sample using a heateddiode sensor
4、device. From this measurement, an estimatedconcentration of TCE in the sample can be determined. AnyTCE remaining in the sample is not measured. Any otherHVOC present in the sample will be reported as TCE.1.2 Procedure A can also be used for screening the head-space above a soil suspected of contain
5、ing HVOC contamina-tion to indicate the presence or absence of HVOC contamina-tion in the soil. Procedure B can also be used for screening theheadspace above a water suspected of containing HVOCcontamination to indicate the presence or absence of HVOCcontamination in the water. For both procedures,
6、any HVOCcontamination remaining in the soil or water is not detected bythis practice.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3.1 ExceptionCertain inch-pound units are provided forinformation only.1.4 This standard
7、does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-tion of regulatory limitations prior to use.NOTE 1The diode sensor is heated to
8、 temperatures ranging betweenapproximately 600 and 1000 C (see 6.1.5) and as a result could be asource of ignition.2. Referenced Documents2.1 ASTM Standards:2D4547 Guide for Sampling Waste and Soils for VolatileOrganic CompoundsD5681 Terminology for Waste and Waste Management3. Terminology3.1 Defini
9、tionsFor definitions of terms used in thisscreening practice, refer to Terminology D5681.4. Summary of Practice4.1 Procedure ATo estimate the concentration of TCE ina soil known to contain TCE contamination, a sample of thesoil is added to a glass jar having an open-top cap with aPTFE-bonded silicon
10、e septum. At the time of screening, thetemperature of the soil in the jar should be approximately 50 to120 F (10 to 49 C). The soil in the jar is shaken and allowedto settle for 10 min, so the TCE can partition into the headspaceabove the soil. After 10 min, the TCE concentration in theheadspace is
11、measured using a heated diode sensor device,which gives a numerical voltage reading. The voltage readingfrom the device is converted to a mg/m3value of TCE in theheadspace in the container. Using this value, an estimatedconcentration of TCE in the soil in mg/Kg can be calculated.Any TCE remaining in
12、 the soil sample is not measured by thispractice. Any other HVOC present in the soil will be reportedas TCE.4.1.1 To use Procedure A to screen a soil suspected ofcontaining HVOC contamination, a sample of the soil is addedto a glass jar having an open-top cap with a PTFE-bondedsilicone septum. At th
13、e time of screening, the temperature ofthe soil in the jar should be approximately 50 to 120 F (10 to49 C). The soil in the jar is shaken and allowed to settle for 10min, so the HVOC can partition into the headspace above thesoil. After 10 min, the heated diode sensor device is used toscreen the hea
14、dspace in the container. The numerical voltage1This practice is under the jurisdiction of ASTM Committee D34 on WasteManagement and is the direct responsibility of Subcommittee D34.01.05 onScreening Methods.Current edition approved July 1, 2011. Published August 2011. Originallyapproved in 2005. Las
15、t previous edition approved in 2006 as D7203-06e1. DOI:10.1520/D7203-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe AS
16、TM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.reading from the device indicates the presence or absence ofHVOC contamination in the soil. Any HVOC contaminationremaining in the soil is not detected by this procedure.4.2
17、Procedure BTo estimate the concentration of TCE inwater known to contain TCE contamination, a sample of thewater is added to a glass jar having an open-top cap with aPTFE-bonded silicone septum. At the time of screening, thetemperature of the water in the jar should be approximately 50to 120 F (10 t
18、o 49 C). The water in the jar is shaken, allowedto settle for 1 min, shaken again, and allowed to settle for 1min, so the TCE can partition into the headspace above thewater. After the sample is allowed to settle for the second time,the TCE concentration in the headspace is measured using aheated di
19、ode sensor device, which gives a numerical voltagereading. The voltage reading from the device is converted to amg/m3value of TCE in the headspace in the container. Usingthis value, an estimated concentration of TCE in the water inmg/L can be calculated. Any TCE remaining in the watersample is not m
20、easured by this procedure. Any other HVOCpresent in the water will be reported as TCE.4.2.1 To use Procedure B to screen water suspected ofcontaining HVOC contamination, a sample of the water isadded to a glass jar having an open-top cap with a PTFE-bonded silicone septum. At the time of screening,
21、the tempera-ture of the water in the jar should be approximately 50 to 120F (10 to 49 C). The water in the jar is shaken, allowed tosettle for 1 min, shaken again, and allowed to settle for 1 min,so the TCE can partition into the headspace above the water.After the sample is allowed to settle for th
22、e second time, theheated diode sensor device is used to screen the headspace inthe container. The numerical voltage reading from the deviceindicates the presence or absence of HVOC contamination inthe water. Any HVOC contamination remaining in the water isnot detected by this procedure.5. Significan
23、ce and Use5.1 The heated diode sensor device used in this practice isselective for HVOCs. Other electronegative compounds, suchas alcohols, ketones, nitrates, and sulfides, may cause a positiveinterference with the performance of the heated diode sensor todetect HVOCs, but to do so, they must be pre
24、sent at muchhigher concentrations than the HVOCs.NOTE 2For volatile organic compound (VOC) screening purposes, aflame ionization detector (FID) selectively responds to flammable VOCs;a photoionization detector (PID) selectively responds to VOCs having adouble bond; and a heated diode sensor selectiv
25、ely responds to haloge-nated VOCs.5.2 This practice can be used for screening media known tocontain TCE to estimate the concentration of TCE in the media.Procedure A is to be used for screening soil known to containTCE and Procedure B is to be used for screening water knownto contain TCE. Both Proce
26、dures A and B involve measuringthe TCE concentration in the headspace above a sample. Fromthis measurement, an estimated concentration of TCE in thesample can be determined. Any TCE remaining in the sampleis not measured by this practice. Any other HVOC present inthe sample will be reported as TCE.5
27、.3 This practice can also be used for screening the head-space above a soil or water suspected of containing HVOCcontamination to indicate the presence or absence of HVOCcontamination in the soil (Procedure A) or water (ProcedureB). Any HVOC contamination remaining in the sample is notdetected by th
28、is practice.5.4 Detection LimitThe detection limit of the heateddiode sensor for TCE is 0.1 mg/m3in air, based on asignal-to-noise ratio of 2. For a 25-g TCE-contaminated soilsample in a 250-mL container, the detection limit of ProcedureA for TCE is 0.001 mg/Kg, assuming complete partitioning ofTCE
29、into the headspace. For a 25-g TCE-contaminated watersample in a 250-mL container, the detection limit of ProcedureB for TCE is 0.001 mg/L, assuming complete partitioning ofTCE into the headspace.5.5 This practice can be used to screen moist soil samplesand water samples. Water vapor does not interf
30、ere with theperformance of the heated diode sensor.5.6 Hydrocarbon fuels, including fuels containing aromaticcompounds, such as gasoline, are not detected by the practice.6. Apparatus6.1 Procedure A and B:6.1.1 Glass Jars, 250-mL (8-oz), approximately 14 cm (512in.) tall, with open-top caps having P
31、TFE-bonded siliconesepta.6.1.2 Scale, capable of weighing to 0.1 g.6.1.3 Thermometer, with temperature given in divisions of0.1 C6.1.4 Barometer, such that pressure in atmospheres can bedetermined to 0.001 atm.6.1.5 Heated Diode Sensor Device, a device having a diodesensor that is heated between tem
32、peratures ranging fromapproximately 600 to 1000 C generating an alkali metal vaporstream that selectively reacts with halogens present in HVOCmolecules, creating ionized product species that cause a currentto flow between a cathode and an anode. The numerical outputfrom the sensor in volts is propor
33、tional to a microamp currentfrom the diode and ranges from 0.001 to 20 V with a resolutionof 0.001 V. The HVOC molecules in the headspace above thesample are drawn through a probe to the heated diode sensor bya pump in the device. The heated diode sensor device shouldhave a needle attached to the pr
34、obe of the device so the septumin the cap of the sample jar can be pierced and the needle canbe inserted into the headspace above the sample. This needlemust be designed to allow make-up air to enter the sample jarfrom the top so that back pressure will not build up within thejar. Back pressure in t
35、he jar will change the air flow rate of thedevice and in turn affect the voltage reading.6.1.6 Tedlar Bags, 1 Lin volume and having a stainless steelvalve with a nipple fitting that can be opened and closed.6.1.7 Gas Regulators, for use with the TCE standard gascylinders (see 7.1). Each regulator sh
36、ould have a short length,about 114 in., of14-in. inner diameter fluoroelastomer tubingattached to the nipple fitting.6.2 Procedure A:6.2.1 Metal or Rigid Plastic Coring Tools, designed forcollecting and transferring a 25-g soil VOC sample (see GuideD4547 and 8.1.1).D7203 1127. Reagents and Materials
37、7.1 TCE Standard Gas CylindersThese are transportablecylinders containing certified concentrations of TCE in airpressurized to about 320 psi. If the practice is being used toscreen a TCE-contaminated media to estimate the concentra-tion of TCE in the media, two concentrations of TCE arerequired. One
38、 concentration is 220 6 10 vapor part per million(ppmv) TCE in air. This is the high concentration TCE standardgas. The other concentration is 22 6 1 ppmv TCE in air, whichis the mid concentration TCE standard gas. These concentra-tions correlate with the upper and mid range of sensor responsefor th
39、e device. A 220 ppmv TCE standard gas at 25 Ccorresponds to about 890 mg/m3TCE in air at 0.75 atm ofpressure and to about 1200 mg/m3TCE in air at 1 atm ofpressure. A 22 ppmv TCE standard gas at 25 C corresponds toabout 90 mg/m3TCE in air at 0.75 atm of pressure and to about120 mg/m3TCE in air at 1 a
40、tm of pressure. See Note 3 andNote 4. If the practice is being used to screen a mediasuspected of containing HVOC contamination to indicate thepresence or absence of HVOC contamination, only the highconcentration TCE standard gas, 220 6 10 ppmv TCE in air, isrequired.NOTE 3For HVOC concentrations in
41、 air that are greater than 10mg/m3, the current that is generated by the reaction between the halogenand the alkali metal vapor when the sensor is exposed to the HVOC is afunction of the log of the concentration of the halogen in air. The log of890 is 2.9, and the log of 1200 is 3.1, showing that th
42、e log values of theseconcentrations vary only slightly. Similarly, the log of 90 is 1.9, and thelog of 120 is 2.1. These values show that the log of the TCE concentrationin air varies only slightly at different elevations (atmosphere of pressure).NOTE 4The mg/m3concentrations of the TCE in the stand
43、ard gascylinders can be calculated using the ppmv concentrations of TCE in thecylinders, the atmospheric pressure, the temperature, and Eq 5 and Eq 6,which are given in 13.6 or Eq 20 and Eq 21, which are given in 18.6.7.1.1 Transportation of the TCE gas cylinders must complywith current Department o
44、f Transportation (DOT) regulations.8. Sample Collection and Preparation8.1 Procedure A:8.1.1 Collect a soil sample of approximately 25 g using ametal or rigid plastic coring tool. See Guide D4547 forrecommended devices. If the sample will be stored in thecoring tool prior to screening, it should be
45、collected using acoring tool designed for sample storage as described in GuideD4547 and should be stored as specified in Guide D4547.8.1.2 Preweigh a 250-mL glass jar with an open-top caphaving a PTFE-bonded silicone septum. Record the mass of thejar with the cap to 60.1 g.8.1.3 Extrude the soil sam
46、ple from the coring tool into thepre-weighed 250-mL glass jar and immediately seal the jarmaking sure that there are no soil particles on the sealingsurfaces.8.1.4 Weigh the jar-plus-soil sample and record the mass ofthe jar-plus-soil sample to 60.1 g.8.1.5 Determine the mass of soil added to the ja
47、r, and recordthe mass of the soil sample to 60.1 g.8.1.6 The temperature of the soil in the sample jar should beapproximately 50 to 120 F (10 to 49 C) prior to screening thesample using the heated diode sensor, so that HVOC partition-ing into the headspace above the sample will occur (see Note5). Th
48、e sample jar should not be opened to determine the soiltemperature. The ambient temperature where the screening isto be performed should be in the range of 50 to 120 F (10 to49 C) (see Note 6), and the soil sample should be allowed tocome to approximately that temperature prior to screening(Section
49、12).NOTE 5The temperature at which the screening is performed mayaffect the HVOC concentration in the headspace. For example, the vaporpressure of TCE at 120 F (49 C) is about seven times greater than thevapor pressure of TCE at 50 F (10 C). Therefore, more TCE would beexpected in the headspace at higher temperatures.NOTE 6The ambient temperature where the screening is to beperformed will be recorded as specified in 11.38.2 Procedure B:8.2.1 Mark a 250-mL glass jar having an open-top capcontaining a PTFE-bonded silicone septum to show the fillingle
