Optimizing the Analysis of Volatile Organic Compounds - Restek

72 pages
0 downs
8 views

Extension: PDF

Please download to get full document.

View again

of 72
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Share
Description
1 Optimizing the Analysis of Volatile Organic Compounds Technical Guide Inside: EPA Method Definitions State GRO Methods Contract Laboratory Program (CLP) The Love…
Transcript
1 Optimizing the Analysis of Volatile Organic Compounds Technical Guide Inside: EPA Method Definitions State GRO Methods Contract Laboratory Program (CLP) The Love Canal Scandal Purge and Trap Theory Sequences and Flow Paths of the Purge and Trap Unit Purge and Trap Components Adsorbent Materials and Traps Troubleshooting Common Problems Associated with Purge and Trap Units GC System Configurations Detection Systems GC/MS Operation Applications www.restek.com 2 www.restek.com Introduction Optimizing the Analysis of Volatile Organic Compounds One of our standing goals is to provide you with practical technical information to help you obtain reliable data from your chromatographic and peripheral systems. This guide presents information on the common US Environmental Protection Agency (EPA) gas chromatogra- phy (GC) methods and procedures used to analyze volatile organic compounds (VOCs). It is a compilation of information based on our experience and that of experts in this field. Much of this guide is dedicated to discussing purge and trap techniques, and showing applications using a variety of configurations and conditions. We would like to thank the following people for their technical contributions to this guide: Jessie Crocket Butler, Applications Chemist Thermo Finnigan, GC & GC/MS Division 2215 Grand Avenue Pkwy Austin, Texas 78728 Laura Chambers, Applications Chemist OI Corporation 151 Graham Road College Station, Texas 77845 Jeff Grindstaff, GC/MS Manager Columbia Analytical 1317 South 13th Avenue Kelso, Washington 98626 Alan Hilling, Lab Supervisor Pace Analytical Services Inc. 9800 Kincey Avenue, Suite 100 Huntersville, North Carolina 28078 Darrell Robbins, GC/MS Volatiles Chemist Severn Trent Laboratories 55 South Park Drive Colchester, Vermont 05446 Glynda Smith, Applications Chemist Tekmar-Dohrmann 4736 Socialville-Foster Road Mason, Ohio 45040 Alex Tam, GC/MS Volatiles Chemist Severn Trent Laboratories 1220 Quarry Lane Pleasanton, California 94566 We hope you enjoy reading this guide and find it useful in your work. If you have any ques- tions, or have input for future editions, please don’t hesitate to contact Restek Corporation - we’ll be happy to hear from you. Christopher English Environmental Innovations Specialist Table of Contents EPA Method Definitions . . . . . . . . . . . . . . . . . . . . .3 Drinking Water Methods (500 Series) . . . . . . . . .3 Wastewater Methods (600 Series) . . . . . . . . . . . .3 Hazardous Waste Methods (8000 Series) . . . . . . .4 State GRO Methods . . . . . . . . . . . . . . . . . . . . . . . .4 Contract Laboratory Program (CLP) . . . . . . . . . . . .5 The Love Canal Scandal . . . . . . . . . . . . . . . . . . . .6 Purge and Trap Theory . . . . . . . . . . . . . . . . . . . . .7 Concentration of Volatile Organics . . . . . . . . . . .7 Sequences and Flow Paths of the Purge and Trap Unit . . . . . . . . . . . . . . . . . . . . .8 Purge and Trap Components . . . . . . . . . . . . . . . . .9 Purge Vessel . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Adsorbent Materials and Traps . . . . . . . . . . . . . . .10 Adsorbent Materials . . . . . . . . . . . . . . . . . . . . .11 Choosing the Right Trap for Your Analysis . . . . .12 Moisture Control Systems- Water and Methanol Management . . . . . . . . . . .13 Transfer Line . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Troubleshooting Common Problems Associated with Purge and Trap Units . . . . . . . . .15 GC System Configurations . . . . . . . . . . . . . . . . . .18 Wide-bore Systems (0.45mm ID and 0.53mm ID columns) . . . . . . . .18 Narrow-bore Systems (0.18mm ID - 0.32mm ID columns) . . . . . . . . . .21 Capillary Column Phases . . . . . . . . . . . . . . . . .21 Metal Columns . . . . . . . . . . . . . . . . . . . . . . . . .22 Detection Systems . . . . . . . . . . . . . . . . . . . . . . . .23 Column Configurations . . . . . . . . . . . . . . . . . . .23 Detector Configurations . . . . . . . . . . . . . . . . . .23 PID Operation . . . . . . . . . . . . . . . . . . . . . . . . . .24 FID Operation . . . . . . . . . . . . . . . . . . . . . . . . . .25 ELCD Operation . . . . . . . . . . . . . . . . . . . . . . . .26 GC/MS Operation . . . . . . . . . . . . . . . . . . . . . . . .30 Applications Using GC Detection Systems . . . . . .37 Applications Using GC/MS Detection Systems . . .50 Tables of Retention Times . . . . . . . . . . . . . . . . . .56 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60 Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 Product Index . . . . . . . . . . . . . . . . . . . . . . . . . .61 3 www.restek.com EPA Method Definitions Many EPA methods have been developed for the analysis of VOCs. Virtually all VOC meth- ods employ purge and trap techniques to concentrate the volatiles from the sample matrix. The type of sample matrix being analyzed determines which method is used. We will discuss drinking water methods (500 series), wastewater methods (600 series), hazardous waste methods (8000 series), and Contract Laboratory Program (CLP) methods. In addition, we will discuss state gasoline range organic (GRO) methods. Drinking Water Methods (500 Series) Proposed in 1973 by the EPA and passed by Congress a year later, the Safe Drinking Water Act (SDWA) establishes national standards for drinking water from surface and ground water sources. These methods regulate the analysis of trace-level organic pollutants in drinking water. Enforcement of the SDWA provides that states shall have the primary authority, while the EPA will oversee activities pertaining to the public water supply system. These methods have evolved over the years, which has resulted in a growing list of compounds of interest in the subsequent revisions. Method 502.2: This capillary column GC method is used to monitor 60 regulated volatile contaminants in drinking water. It employs a purge and trap concentrator, combined with a photoionization detector (PID) and an electrolytic conductivity detector (ELCD) in series. The PID detects aromatic and double-bond compounds, and the ELCD detects halogenated compounds. Method 504: This capillary column GC method is used to monitor ethylene dibromide (EDB) and dibromochloropropane (DBCP) in drinking water. It employs microextraction, using hexane, and analysis using an electron capture detector (ECD). Method 524.2: This capillary column GC/mass spectroscopy (GC/MS) method is used to monitor the same 60 drinking water contaminants listed in Method 502.2. It also employs purge and trap concentration, but uses the MS to determine both aromatic and halogenated compounds. Method 524.2, Revision IV: This capillary column GC/MS method is used to monitor the 60 compounds listed in Methods 524.2 and 502.2, plus 24 additional compounds. As of Fall 2001, revisions were proposed to replace hydrochloric acid sample preservation with sodium thiosulfate. These revisions, however, were not promulgated at the time of this printing. Wastewater Methods (600 Series) In 1977, President Carter signed the Clean Water Act (CWA) allowing the EPA to study and, if necessary, regulate 65 priority wastewater pollutants. A cooperative effort between envi- ronmental laboratories and the EPA resulted in the final version of what are now known as the 600 series methods. These methods regulate the analysis of organic pollutants in industri- al and municipal wastewater discharges. They were written for packed GC columns, but most environmental laboratories now use capillary column technology. Method 601: This GC method was developed to monitor 29 halogenated volatile pollutants in wastewater. It employs purge and trap concentration combined with an ELCD. Method 602: This GC method was developed to monitor seven aromatic volatile pollutants in wastewater. It employs purge and trap concentration combined with a PID. Many labora- tories combine Methods 601 and 602 by using a PID and an ELCD connected in series. Method 624: This GC/MS method uses purge and trap concentration to monitor 35 halo- genated and aromatic volatile pollutants in wastewater. Method 1624: This isotope dilution GC/MS method uses purge and trap concentration to monitor 58 volatile pollutants in wastewater. Stable, isotopically labeled analogs of the target compounds are added to correct for analyte recoveries that might vary due to matrix interfer- ence in the analyzed samples. 44 Hazardous Waste Methods (8000 Series) The Resource Conservation and Recovery Act (RCRA) of 1976 was enforced shortly after front-page headlines revealed the presence of serious hazardous waste sites like Love Canal, NY and Times Beach, MO. The analytical methods for determining hazardous waste, known as the 8000 series methods, fall under US EPA SW-846. These methods were designed for monitoring organic pollutants in waste samples prior to disposal at hazardous waste facilities. They also can be used for monitoring groundwater at these facilities. Method 8010B: This packed column GC method is used to monitor 50 halogenated volatile pollutants in hazardous waste samples. It employs purge and trap concentration and an ELCD. Method 8011: This capillary column GC method is used to monitor 1,2-dibromoethane (EDB) and 1,2-dibromo-3-chloropropane (DBCP) in hazardous waste samples. It employs microextraction, using hexane, and analysis using an ECD. Method 8015A: This packed column GC method is used to monitor non-halogenated volatile pollutants in hazardous waste samples. It employs purge and trap concentration and an FID. Total petroleum hydrocarbon analysis, commonly refered to as 8015-TPH, also falls under this method. Method 8015-TPH uses an FID to match a known pattern of gasoline with an unknown sample containing peaks that fall within the gasoline pattern range. If a pattern falls within the gasoline window it may be reported as gasoline. Method 8020A: This packed column GC method is used to monitor ten aromatic volatile pollutants in hazardous waste samples. It employs purge and trap concentration and a PID. It is common for analysts to combine Methods 8010 and 8020, by using a PID and an ELCD in series. Method 8021A: This capillary column GC method is used to monitor 60 volatile contami- nants in hazardous waste samples. It employs purge and trap concentration, combined with a PID and an ELCD in series. The PID detects aromatic compounds and double-bond com- pounds, and the ELCD detects halogenated compounds. Method 8021B: Using the same analytical technique as Method 8021A, the compound list for Method 8021B includes ten additional compounds but does not require the analysis of several branched aromatics and halogenated compounds. Method 8240B: This packed column GC/MS method is used to monitor 79 volatile pollu- tants in hazardous waste samples. It employs purge and trap concentration for most ana- lytes, but direct injection can be used for some limited applications. Method 8260B: This capillary column GC/MS method is used to monitor 98 volatile pollu- tants in hazardous waste samples. It employs purge and trap concentration for most analytes, but direct injection can be used for some limited applications. State GRO Methods Leaking underground storage tanks (LUST) pose significant environmental risks throughout the country. States have the responsibility to develop LUST testing methods. State gasoline range organics (GRO) methods are based on EPA methods such as 602, 8020 and 8015. The most common EPA method used is 8015, which relies on baseline-integrating the total area of the gasoline fingerprint, using marker compounds such as hexane (C6) and dodecane (C12). The 8015-TPH Method analysis uses an FID and pattern recognition—the specific ratio of peaks that make up a particular fuel—to identify the type of fuel. If a pattern falls within the window markers it may be reported as gasoline, then quantified. Difficult matrices can result in misiden- tification or poor quantitation of the sample, and deterioration in the environment (weathering) further complicates the analysis. Therefore, many states have combined EPA methods, using a PID/FID in series (e.g., Methods 8020/8015-TPH). Specific aromatic compounds are analyzed using PID (Methods 602, 8020), which is connected to the FID (Method 8015-TPH). The com- mon target compounds are benzene, toluene, ethylbenzene, and m-, o-, and p-xylene (BTEX), however many states also have added other compounds to their methods (Table I). Drinking Water Disinfection Byproducts 1996 amendments to the SDWA require the EPA to review and revise existing National Primary Drinking Water Regulations (NPDWR) at least once every six years. Much of this renewed interest in changes to drink- ing water regulation standards stems from studies suggesting negative reproductive effects, such as spontaneous abortions, resulting from trihalomethanes (THMs) in water. Current studies using compliant levels of THMs in water have revealed adverse reproductive effects, therefore method detec- tion limits (MDLs) will continue to be lowered in methods that address THMs.1 1. S. Richardson, Anal. Chem. 73 (2001) 2719-2734. www.restek.com 55 www.restek.com Contract Laboratory Program (CLP) In 1980 the US Congress addressed the cleaning of the most contaminated abandoned and inactive dumpsites. This new legislation was known as the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) and the Superfund Amendments and Reauthorization Act (SARA). These acts required cleanup of the sites and the prosecution of those responsible for the contamination. The methods monitor volatile pollutants at Superfund sites. Method OLM04.1 (04.2): The US EPA has awarded contracts for organic low-medium (OLM) concentration samples within the Superfund program under the 04.2 revision Statement of Work (SOW). This is a capillary column GC/MS method used to monitor in hazardous waste 50 volatile pollutants that fall under CERCLA and SARA guidelines. While this method employs purge and trap concentration, direct injection can be used for higher concentration samples that require extraction with methanol. Method OLC03.2: This new EPA Statement of Work (SOW) describes analytical methods for aqueous low concentration organics. This capillary GC/MS method adds nine new volatile compounds to the OLC03.1 target compound list (TCL), for a total of 52 com- pounds. Deuterated Monitoring Compounds (DMC) are introduced as a sample-by-sample accuracy indicator. Where can EPA methods be obtained? Drinking Water Methods (500 Series) National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 703-487-4600 Wastewater Methods (600 Series) Environmental Monitoring and Support Laboratory U.S. EPA Cincinnati, OH 05268 513-569-7562 Hazardous Waste Methods (8000 Series) U.S. Government Printing Office Washington, DC 20402 202-783-3238 Websites: U.S. EPA Homepage www.epa.gov Federal Register Link www.epa.gov/fedrgstr/ Ground Water/ Drinking Water (500 Series) www.epa.gov/safewater/ Wastewater Office (600 Series) www.epa.gov/OWM/ Solid and Hazardous Waste (8000 Series) www.epa.gov/epaoswer/osw/ Updated List of EPA Methods and Web Locations www.epa.gov/region01/oarm/testmeth.pdf Table I. State gasoline methods include specific compounds. State Method-Specific Compounds Alaska (AK101AA) BTEX, branched aromatics Arizona BTEX, C6-C32 California BTEX, MTBE California (WIP) Method 8020, MTBE Connecticut GRO Florida PVOC Georgia GRO Method 8015B Iowa (OA-1) GRO, BTEX, MTBE Louisiana GRO (C6-C12) Maryland GRO Method 8015B Massachusetts (VPH) BTEX, m-naphthalene, MTBE, etc. Michigan (GRO) BTEX, m-naphthalene, MTBE, etc. Mississippi GRO Missouri (OA-1) GRO, BTEX, MTBE Montana Method 8015 New York GRO Method 8015B North Carolina Massachusetts VPH Oklahoma GRO Oregon C5, C6, C8, C10, C12, BTEX, MTBE, etc. Pennsylvania (DEP) BTEX, MTBE, 1,2-dibromoethane, 1,2-dichloroethane South Carolina GRO Method 8015B Tennessee GRO Texas (TNRCC 1005) hexane, decane (locator mix) Utah BTEX, MTBE, naphthalene Virginia GRO Method 8015B Washington (VPH) C5, C6, C8, C10, C12, BTEX, MTBE, etc. West Virginia Method 8015B Wisconsin PVOC/GRO BTEX, MTBE, naphthalene, TMB, 1,3,5-TMB Acronyms: BTEX - benzene, toluene, ethylbenzene, xylenes MTBE - methyl-tert-butylether GRO - gasoline range organics PVOC - petroleum volatile organic compounds VPH - volatile petroleum hydrocarbons TMB - trimethylbenzene. 66 The Love Canal Scandal In the early 1900s William T. Love started work on his dream—to build a canal between the upper and lower Niagara Rivers to generate power for a planned model city. Before the canal was a mile long, the economy failed—and with it, Love's dream. Hooker Chemical purchased the land in 1920 and for the next three decades the City of Niagara, the US Army, and Hooker dumped waste into the canal. Eventually, the dump was filled and a clay cap was placed over the waste site. Soon after, the city persuaded Hooker to sell the property for $1 with the threat of the Constitution's imminent domain clause. Although Hooker added a lengthy disclaimer to the property deed detailing the toxic nature of the site, within two years sewer lines were dug into the clay cap that had sealed the waste from leaching to the surface. In the late 1950s, about 100 homes and a school were built near the 20,000 tons of waste (Figure 1). Heavy snow and rainfall in 1975 and 1976 caused high water levels, which exposed the 55-gallon drums (Figure 2). Niagara Gazette reporter Michael Brown broke the story, explaining that many residents were living on a toxic waste dump. From the time the families moved in during the ’50s they had noticed strange odors, and in the early ’70s a tar-like substance was reported in many basements. Analysis using the 8000 series methods, and later the 600 series and CLP methods, identified 248 chemicals, including 2,3,7,8-tetrachlorodibenzo-p-dioxin, which is believed to be the most toxic substance known to man. Many VOCs were discovered in the ground, water, and air—most notably benzene—a known carcinogen. There were no toxico- logical data available for 100 of the 248 compounds. On August 2, 1978 state health offi- cials ordered all pregnant women and children under the age of two to leave the area. A week later, with headlines across the country detailing the Love Canal disaster, President Carter approved the immediate evacuation of 221 families. That number would soar to near- ly 900 families by the time this tragedy completely unfolded. This was the first environmental disaster given daily front-line media coverage. It was a turning point for environmental awareness and ultimately helped to shape the environmental testing methods that are used today for the identification of VOCs in air, water, and soil. The combined efforts of environmental laboratories, engineering firms, and regulatory agencies have evolved since Love Canal to protect the public and ultimately save lives. Figure 2. Four decades after dumping, toxic waste drums like these were exposed at Love Canal, NY. Figure 1. www.restek.com Infrared aerial photo of Love Canal area (spring 1978) showing 99th Street elemen- tary school (center), two rings of homes bordering the landfill, and LaSalle Housing Development (upper right). White patchy areas are barren sections where vegetation will not grow, presumably due to leaching chemicals. Image courtesy of State University of New York at Buffalo University Archives. We thank Dan Di Landro, Visiting Assistant Librarian, for help with obtaining the photograph. 7 www.restek.com gas source 5 4 3 2 1 6 Figure 3. Volatile analyte in equilibrium between the gas and sample phases. Sample purging in progress in a Tekmar 3100 concentrator. G=gas phase (headspace) The gas phase, commonly referred to as the he
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks