Environmental Industry and Regulated Testing

A common technique for the sampling of Volatile Organic Compounds (VOCs) is purge and trap concentration. During purge and trap concentration, the sample to be extracted is either placed in an airtight vial with no headspace or introduced into an airtight chamber and mixed with water. An inert gas such as helium or nitrogen is bubbled through the water; this is known as purging or sparging.

The volatile compounds move into the headspace above the water and are drawn along a pressure gradient onto an adsorbent trap. Next, the trap is heated and the sample compounds are introduced to the GC column via a second heated transfer line, which is in line with the split inlet system on the GC or GC/MS. Purge and Trap in conjunction with a GC is well suited for volatile organic compounds (VOCs) and BTEX compounds (aromatic compounds associated with petroleum) in environmental samples and can also be used to sample volatile aromatic analytes in food and flavor samples.

The United States Environmental Protection Agency (USEPA) has promulgated a number of methods for the determination of VOCs. VOCs can be found in air, water and soil. The USEPA determinative methods include USEPA Methods 8260, 624, 8021 and 524 while the purge and trap preparative methods are USEPA Methods 5030 and 5035.

USEPA Method 5030 describes the purge and trap sampling of water and water miscible samples while Method 5035 describes the sampling of high concentration soil and waste sample extracts. Both of these sampling techniques can be done by the Evolution Purge and Trap concentrator and are outlined as proper sample preparation techniques for Method 8260D which involves employing a GC/MS for the VOC determinative technique. Other determinative methods that utilize the Evolution purge and trap are Method 8015 for the determination of gasoline compounds using GC/FID and Method 8021 which examines gasoline fractions by GC/PID. In order to determine VOCs in drinking water, the USEPA promulgated Method 524.

Application Types

Drinking Water - Purge and Trap EPA 524

Method 524.2 encompasses 84 volatile organic compounds (VOCs) including trihalomethanes which are common byproducts of disinfection. Sample size can be as high as 25mL to as low as 5mL as long as the analytical system can reach the required detection limits. Samples need to be purged at 40mL/min with Helium for 11 minutes and desorbed for about 4 minutes. Since USEPA Method 524.2 is a prescriptive method, these purge and trap parameters may not be altered. There are some who experience excess moisture due to the longer desorb time in this method. Moisture can negatively affect resulting chromatography. If your compliance officer is mandating a 4 minute desorb, ask about EST’s patented Desorb Flow Control (DFC) available on the Evolution 2.

Over the years, there have been many improvements to purge and trap and Gas Chromatography/Mass Spectrometry (GC/MS) systems. They have better sensitivity and are much more efficient in analyte separation and analysis. For this reason, USEPA Method 524.2 was updated with USEPA Method 524.3 and 523.4 with the Method 523.4 allowing for laboratories to use Nitrogen as a purge gas. There are several updates to the drinking water method and right now laboratories can choose which method that they would like to use.

Whitepapers

The United States Environmental Protection Agency (USEPA) created Method 524.2 for the examination of purgeable organic compounds in surface, ground and drinking water. There are a wide range of compounds listed in the method including four trihalomethanes which form when water is chlorinated. This application will examine USEPA Method 524.2 employing the new Evolution 2 purge and trap concentrator.

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In June 2009, the United States Environmental Protection Agency (USEPA) promulgated a new drinking water method, 524.3. Due to advances in analytical instrumentation, Method 524.3 allows laboratories to modify purge and trap and GCMS conditions. Currently the USEPA is investigating the option of using Nitrogen as the purge gas in a new drinking water method, 524.4.

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During volatile analysis, samples are purged with an inert gas in order for the Volatile Organic Compounds (VOCs) to be swept out of the sample matrix and onto an analytical trap. For years, the established purge flow rate and time has been 40ml/min for 11 minutes. USEPA Method 524.3 changed this. This new method allows for different purge flows and times and outlines recommended and allowable ranges. This application will examine how different purge flows and times affect compound performance for Method 524.3.

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Desorb flow control was developed in order to help manage the moisture associated with the four minute desorb time required for USEPA method 524.2. An added benefit to this process is the reduction in helium consumption when using this technique. This application will explain the patented process of Desorb Flow Control (DFC) (United States Patent Office numbers: 8062905, 7951609, 7803635) for helium conservation and moisture control.

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The compounds 2-Methylisoborneol (2-MIB) and Geosmin are the primary source of the foul odor found in drinking water. Algal contamination is the principal cause of the formation of these compounds. Geosmin and 2-MIB have such a low odor threshold that even the slightest amount can produce an unpleasant odor and taste in drinking water. Thus, developing a reliable sampling and analysis platform for very low level detection is important. Standard Method 6040D describes a procedure for the detection of 2-MIB and Geosmin using Solid Phase Micro Extraction (SPME) coupled with a Gas Chromatograph (GC) and Mass Spectrometer (MS). Selective Ion Monitoring (SIM) is used for compound detection down to part per trillion (ppt) levels. This examination will optimize the sampling and detection of 2-MIB and Geosmin.

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Algal contamination in drinking water is becoming a common problem. The primary compounds that result from this contamination are 2-Methylisobomeol (2-MIB) and Geosmin. These compounds cause a musty odor in water and since the odor of these compounds have a very low threshold for detection, small amounts of contamination can cause drinking water to taste and smell unpleasant. This application note will investigate the detection of 2-MIB and Geosmin down to a 1ppt level.

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Geosmin and 2-Methylisoborneol have an unpleasant odor and a very low odor threshold. The aroma of these compounds can be detected by smell at levels below ten parts per trillion. Thus, developing a reliable sampling and analysis platform for low-level detection is important. The use of Solid Phase Micro Extraction for the sampling of Geosmin and 2-Methylisoborneol is described in Standard Method 6040D. This application will examine the difference between two SPME sampling devices for the extraction of these compounds.

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The United States Environmental Protection Agency released Method 524.3 with some changes that incorporated some of the advances in purge and trap technology. One of those modifications allowed for the purge flow and time to be revised in order to make the purge and trap cycle times shorter and allow laboratories to be able to test more samples. This application will examine two different purge flows and times and compare the corresponding results.

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Purge and Trap EPA 8260 and EPA 624

Method 8260 incorporates several preparative techniques including purge and trap (USEPA Method 5030 and 5035) and headspace sampling (USEPA Method 5021). For wastewater compliance monitoring the USEPA promulgated Method 624. This method is used for the determination of VOCs in municipal and industrial waste water using purge and trap sampling. Since Method 8260 and 624 both involve water matrices, many laboratories run an extended compound list in order to accept both types of water samples.

USEPA Method 8260 encompasses over 100 compounds, many of which can be determined using a purge and trap preparative technique. Method 5030 describes the purge and trap procedure for the determination of VOCs in water or water miscible samples. While Method 5035 applies to solid, oil, sludge or tar… matrices. Both methods involve purge and trap sampling in conjunction with Gas Chromatography/Mass Spectrometry (GC/MS) for the determination of the VOCs.

Whitepapers

USEPA Method 8260D is a procedure that uses Gas Chromatography and Mass Spectrometry in order to determine Volatile Organic Compounds (VOCs). There are several preparative methods used in conjunction with this practice. USEPA Method 5030, for waters, and Method 5035, for soils and waste, are the purge and trap preparative methods for volatile organic analysis. This application will examine purge and trap sampling of VOCs in water and soil matrices.

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USEPA Method 8260D employs purge and trap preparative techniques for the examination of volatile compounds. Historically, labs use helium gas to purge the volatile compounds out of the matrix. However, in recent years, Helium has become more difficult to find, so labs have been forced to find an alternative to Helium. Nitrogen gas provides an excellent substitute for Helium. This application will examine the determination of volatile organic compounds using Nitrogen as the purge gas.

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Over the past decade, the need for environmental laboratories using purge and trap systems to report at or below the Method Detection Limit (MDL) has created many new challenges. As a result of the required lower detection levels, water management, analyte migration and carryover reduction have become a critical concern to meet linear calibration criteria. This paper will present the optimum purge and trap system parameters used to generate USEPA Method 8260B data. The conditions utilized will provide the necessary sensitivity, linearity and accuracy compliant to the method. In particular, the revolutionary advancements used to virtually eliminate carryover and manage the moisture will be highlighted. Analytical results including calibrations factors, method detection limits and reproducibility data will be presented.

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The United State Environmental Protection Agency (USEPA) Method 8260 recommends an eleven-minute purge time at 40ml/min purge flow. Due to this restriction, environmental analysts need to investigate other means to decrease cycle times without sacrificing analytical results. This application note will examine decreasing cycle times within the USEPA Method requirements.

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Helium is the second most abundant element in the universe but makes up only 0.0005% of the earth’s atmosphere. Helium has many uses including cooling superconducting magnets for Nuclear Magnetic Resonance (NMR) or Magnetic Resonance Imaging (MRI), and since it is inert, it can also be used as a carrier gas for Gas Chromatography/Mass Spectrometry (GC/MS). During purge and trap concentration, Helium is used to purge volatile analytes out of the sample matrix in order to concentrate them onto an analytical trap. Due to the Helium shortage, it has become necessary to find another means of purging analytes out of the sample. This application will examine using Nitrogen as the purge gas for purge and trap sampling.

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Carryover is a common problem resulting in sample reruns and reduced productivity in environmental labs. Many advances over the years have been developed to tackle this issue. These innovations vary from increasing bake times and bake flows to changing the flow path tubing to more inert materials. This application will evaluate a patented innovation for cleaning the sparge vessel during an analytical sequence.

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The United States Environmental Protection Agency (USEPA) Method 624 is employed to determine purgeable industrial pollutants in environmental samples. The latest revision is based on the previous method. However, due to the many updates to sampling and analysis instrumentation, many of the method requirements can be more stringent than is required in the method.

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1,2,3-Trichloropropane (1,2,3-TCP) is usually found at industrial waste sites. It can be used as a solvent or as a degreasing agent and is also a chemical intermediate when synthesizing other compounds. 1,2,3-TCP does not typically leach into soil, thus it is commonly found in ground water. Since it is a highly carcinogenic chemical and has been found to be a common contaminant in ground water, California has established 1,2,3-TCP as a hazardous compound with a notification level of 0.005-micrograms per liter (μg/L) in drinking water. While in Europe, 1,2,3- TCP is listed as a substance of very high concern that may cause cancer and is toxic for reproduction. This application will examine purge and trap sampling in conjunction with Gas Chromatography/Mass Spectrometry (GC/MS) for the determination of low levels of 1,2,3-Trichloropropane.

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1,4-Dioxane is commonly used as a cleansing agent during the manufacture of pharmaceuticals. It is also employed as a stabilizer for chlorinated solvents, so it is commonly found at industrial sites contaminated with these solvents. The Environmental Protection Agency (EPA) has classified 1,4-dioxane as a likely carcinogen and thus it is essential to be able to detect 1,4-dioxane at low concentration levels.

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The United States Environmental Protection Agency (USEPA) Method 8260 has an extensive list of analytes that can be analyzed by purge and trap sampling. Two of the more troublesome compounds on this list are Ethanol and 1, 4-Dioxane. Both of these compounds are water miscible and Selective Ion Monitoring (SIM) is required in order to detect these compounds at lower levels. This application will compare linearity, method detection limits, precision and accuracy and carryover of several purge and trap sampling parameters.

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The efficiency of a Gas Chromatograph depends significantly on the type of column that is installed in it. In order to properly separate every compound in a mixture from each other, the optimum column must be used. In this study we will be using Method 8260D of the United States Environmental Protection Agency (USEPA) in order to compare two 624 phase columns with dimensions 30m x 0.25mm x 1.4μm and 20m x 0.18mm x 1.0μm.

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The United States Environmental Protection Agency (USEPA) Method 8260 is used in order to ascertain volatile organic compounds in waters, soils and solid waste samples. Often times, soil and solid waste samples are so highly contaminated the sample needs to be dispersed in methanol. Sample collection for contaminated soils can be obtained in two ways. One, dispersing a bulk soil sample into a 40ml vial and adding methanol in the lab or two, sending pre-weighed vials with a septum sealed cap that already contains the pre-requisite methanol out in the field for soil sampling. No matter how the soil sample is dispersed in methanol, an aliquot of the methanol extract needs to be added to water and purged using USEPA Method 5030. This application will investigate automated sampling of methanol soil extractions.

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Environmental laboratories are always searching for techniques to increase productivity. However, environmental methods demand a large amount of background information in order to ensure sampling and analysis is compliant. The determination of Volatile Organic Compounds (VOCs) in the United States Environmental Protection Agency (USEPA) Method 8260 encompasses many different matrices and in doing so has numerous sampling, quality control, and calibration requirements. The matrices of Method 8260 samples can also vary from air to sludge and from clean to extremely contaminated. Furthermore, the method has an extensive calibration range. All of these factors play into the complexity of sampling and analysis thus, creating ways to streamline sampling while still maintaining sample integrity and method compliance is always of interest to environmental laboratories.

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Volatile contaminants in drinking, ground and wastewaters are an ongoing environmental concern throughout the world. Testing for these contaminants is generally done using a Gas Chromatograph (GC) coupled to a Mass Spectrometer. However, sampling for these compounds is dependent on the environmental regulations of the country in which you are testing. The USEPA methods for extracting VOCs from environmental samples require purge and trap sampling. On the other hand, in Europe and Canada, it is common to use static headspace sampling for the measurement of VOCs.

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Polycyclic Aromatic Hydrocarbons (PAHs) are formed from incomplete burning of carbon containing fuel. There are thousands of PAH compounds in the environment, and of those; there are several that have been established to begin with of concern for the environment. Extraction of PAH compounds involves a large amount of sample and solvent, and because of this, there is a lot of solvent waste. The use of Large Volume Injection (LVI) in conjunction with a Programmable Temperature Vaporizer (PTV) aids in eliminating some of this solvent waste, and reduces labor and shipping costs due to the ability to extract smaller volumes of sample without sacrificing sensitivity. This analysis will compare PAH compound response of a standard injection versus a large volume injection.

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Due to current events, the importance of determining volatile petroleum hydrocarbons in both soils and waters has become an issue. The complexities of the matrices that these compounds are found in can also inhibit accurate detection. Analysis of volatile petroleum hydrocarbons by purge and trap concentration in conjunction with GC/MS will be presented in this poster.

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Environmental testing laboratories are always trying to find ways to increase sample throughput using purge and trap. One of the larger problems laboratories incur is highly contaminated, “hot”, samples. If a sample is hot, there is the possibility of contaminating the purge and trap concentrator. Cleaning up this contamination is as problematic as it is time consuming and therefore negatively impacts sample throughput. There are several ways to get around this challenge each with its own benefits and drawbacks. One potential solution is using Solid Phase Micro Extraction (SPME). This application will examine the efficacy of ASTM Method D-6889, “Fast Screening for Volatile Organic Compounds in Water Using Solid Phase Microextraction (SPME)”, for environmental sample screening.

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Method HJ639-2012 was implemented March 1st, 2013. The method recommends an analytical trap composed of 1/3 Tenax 1/3 silica gel 1/3 active carbon or a “C” trap. As the method requires a two minute desorb time, the silica gel in the C trap can be problematic. This application will compare the C trap with the Vocarb 3000 trap for their efficacy when following the HJ-639 method.

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The Environmental Protection Agency (EPA) has classified 1,4-Dioxane as a likely carcinogen that does not break down readily. Purge and trap concentration and liquid-liquid extraction are the most common techniques for the sampling of 1,4-Dioxane. Each of these techniques has its advantages and drawbacks. This application will explore Solid Phase Microextraction as a possible option for the sampling of 1,4-Dioxane.

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During volatile analysis, samples are purged with an inert gas in order for the Volatile Organic Compounds (VOCs) to be swept out of the sample matrix and onto an analytical trap. For years, the established and recommended purge flow rate and time has been 40ml/min for 11 minutes. However advances in instrumentation technology have led to the potential for greater efficiencies in conducting VOC analysis. This study reviews four sets of time and flow parameters and their respective outcomes.

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Dissolved Gasses RSK

In order to test for  dissolved gases associated with Hydraulic Fracturing, the RSK-175 standard operating procedure (SOP) was developed. This SOP involves some manual preparation of the water samples before the water can be analyzed. In 2017, the American Society for Testing and Materials (ASTM) published a standard for the determination of dissolved gases in water, D8028. ASTM method D8028 standardizes the sampling and analysis of dissolved gases and provides the opportunity to automate the sampling process.

The LGX50 was designed to automate ASTM Method 8028. The automation of this analysis (patent pending) involves using two sample trays, one tray to hold empty 40ml vials with a stir bar and one tray to hold the dissolved gas samples. The LGX50 evacuates the empty vial. Next, the sample is transferred from the full vial to the empty vial thus creating a headspace that retains the sample integrity by not exposing the sample or the sample pathway to the atmosphere. The system then heats and stirs the sample for a prescribed time. Finally, the sample is pressurized so as to fill a sample loop and transfer the sample to the GC/FID for analysis.

Whitepapers

The RSK-175 standard operating procedure was developed in order to determine the amount of dissolved gas in water. However, since the RSK-175 standard is a standard operating procedure and not a formal method, there have been many interpretations and modifications of RSK-175 in order to determine the amount of gas dissolved in the water. This paper will consider three different approaches for dissolved gas calibration and analysis and the respective pros and cons.

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In order to test for possible dissolved gas contamination, most laboratories refer to a standard operating procedure entitled “RSK-175”. This procedure calls for static headspace sampling of the water samples and calculating the amount of dissolved gas using Henry’s Constant. However, as RSK-175 is standard operating procedure and not a formal method, interpretations can vary. In order to address this issue, a formal method is currently being written by American Society for Testing and Materials (ASTM) Committee D-19. This application will test for dissolved gases using the procedures established in the ASTM method.

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Tapping the natural gas reservoirs throughout the United States has long been a viable solution for energy independence; however until recently getting to these gas reservoirs was very difficult. Now, through the development of horizontal drilling in conjunction with hydraulic fracturing or “fracking”, these reservoirs have become much easier to tap for natural gas. However, there are some environmental concerns with the fracking process that have come to light as fracking has gained popularity. One major concern is the potential for natural gas to migrate into drinking water sources. In order to test for dissolved gases, the RSK-175 Standard Operating Procedure (SOP) was developed. Since RSK-175 is an SOP and not an EPA or ASTM method; laboratories have employed different approaches in order to calibrate for the dissolved gases. This study will evaluate a standard calibration using serial dilutions of saturated gas samples. The LGX50 autosampler will do the rest of the work by creating headspace in the sample vial while maintaining sample integrity and transferring the headspace to a GC/FID for analysis. This automation provides the capability to treat calibration samples in the same manner as field samples thus reporting field sample results requires no back calculation using the Henry’s Constant.

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Due to the expansion of natural gas drilling through horizontal fracturing, there has been increased interest in the RSK-175 Standard Operating Procedure (SOP) for the determination of dissolved gases in water. This paper will discuss calibration by using static headspace sampling of vials spiked with different volumes of mixed gases. Furthermore, the precision and accuracy of the calibration will be established by headspace screening of mixed gas standards and also by examining known concentrations of dissolved gases and back calculating experimental results using the Henry’s Constant and the saturated gas calculation.

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The American Society for Testing and Materials (ASTM) Method D8028 is a method to determine dissolved gases in water. The method describes calibration and sampling techniques. One of the recommendations is to ensure the sample is sealed in order to safeguard the integrity of the sample. This recommendation is taken from United States Environmental Protection Agency (USEPA) Method 5030C used for the sampling of volatile organic compounds in water. Many environmental labs currently open their dissolved gas samples in order to place them in a headspace vial for sampling and analysis. This application will compare the efficacy of ensuring the sample is sealed versus opening the sample and pouring it into the sample vial for analysis.

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Hydraulic fracturing or “fracking” has become a commonplace technique for the recovery of natural gas from deep beneath the earth’s surface. As a consequence, there has been a rise in the concern of gases escaping during the “fracking” process and contaminating nearby water sources. Testing for dissolved gases has, until recently, been done following the RSK-175 standard operating procedure. However, as RSK-175 is not an accredited method, different interpretations of the method have been employed. In order to address this issue, a formal method has been published by the American Society for Testing and Materials (ASTM) Committee D-19. This application will test for dissolved gases using a Certified Reference Material (CRM) for Methane, Ethane, Ethylene and Propane using the procedures outlined in the D-8028 ASTM method.

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Sample Preparation

Sample preparation is one of the most important steps in analytical chemistry. Preparation can vary from extractions to dilutions to standard preparation. Attention to detail and accuracy are essential. Automation can remove costly errors and improve precision and accuracy while protecting the analyst from repetitive motion injuries and toxic substances.

Quantitative analysis requires not only sample prep but also standard prep. When preparing a calibration curve, the analyst has to follow a recipe in order to ensure standard accuracy. Any error in the standard preparation and the calibration curve will need to be re-prepped and re-run. Thus, valuable time and resources are wasted.

The EST FLEX 2 Robotic Sampling Platform is capable of performing standard preparation and liquid/liquid extraction for small volumes. The FLEX 2 can be placed on your benchtop for sample prep or installed on top of a GC system for both sample prep and sample analysis automation.

Whitepapers

The preparation of Volatile Organic Standards (VOCs) for the United States Environmental Protection Agency (USEPA) Method 8260D is a tedious prospect. Since the analytes in Method 8260D are volatile, standard preparation can be challenging. This application will demonstrate the capability to automate standard preparation for volatile organic standards.

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Sample preparation is one of the most important steps in analytical chemistry. Attention to detail and accuracy are essential. For these reasons, many laboratories are interested in automating sample preparation procedures so as to limit the possibility of human error. This application will explore automated standard preparation of Poly Aromatic Hydrocarbon (PAH) compounds for USEPA Method 8270.

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Extraction of Poly Aromatic Hydrocarbon (PAH) compounds from water involves using a large volume of solvent. The advent of more sensitive Mass Spectrometers (MS) coupled with Large Volume Injection (LVI) onto the Gas Chromatograph (GC) has aided in better detection of PAH compounds. In consequence, micro-extraction of PAH compounds from water has become a viable solution for sample preparation. This application will investigate an automated liquid-liquid extraction technique for the preparation of PAH water samples.

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