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.
Drinking Water 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.
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.
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.
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.
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.
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.
Algal contamination in drinking water is becoming a common problem. The primary compounds that result from this contamination are 2-Methylisoborneol (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.
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.
The primary sources of the foul odor found in drinking water are the compounds 2-Methylisoborneol (2-MIB) and Geosmin. The compounds are formed from algal contamination. The low odor threshold of Geosmin and 2-MIB is so slight that even the faintest amount can produce an unpleasant aroma in drinking water. Standard Method 6040D describes a procedure for the detection of 2-MIB and Geosmin using Solid Phase Micro Extraction coupled with a Gas Chromatograph and Mass Spectrometer.
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.
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.
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.
USEPA Method 8260 is a procedure used to determine Volatile Organic Compounds (VOCs) in a variety of matrices. The VOCs are sampled and introduced to a Gas Chromatograph (GC) via purge and trap, direct injection or distillation with purge and trap being the most commonly used technique for VOC preparation. In July of 2018, the USEPA released Method 8260D, this new method incorporated several changes including new BFB tune criteria, analyte additions, and blank requirements.
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.
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.
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.
This application will scrutinize Purge and Trap sampling coupled with Gas Chromatography and Mass Spectrometry (GC/MS) for the analysis of volatile organic compounds (VOCs) in industrial discharges and other environmental samples. With the number of organic pollutants in use increasing, the potential for continued contamination of water resources still exists. This leads to the need for updated laboratory sampling and analysis instrumentation; environmental methods must meet certain criterion to account for these changes.
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 (1,2,3-TCP). 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.
1,4-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.
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.
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.
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. This application will investigate automated sampling of methanol soil extractions.
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 and onto an analytical trap. Purge flows and times are recommended by the United States Environmental Protection Agency (USEPA). For years the USEPA recommended purge flow and time was 40ml/min for 11 minutes, however in USEPA Method 524.3 and 4 there is approval to vary purge flows and times.
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 method also 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.
EST Analytical has developed a syringe feature for the CENTURION Autosampler that can dilute samples up to 400 times the original concentration. This feature is fully programmable and the sample vial does not have to be compromised in order to dilute the sample because the dilution process is automated. The sealed vial can be placed in the sample tray while the CENTURION does all of the work.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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. 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.
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.
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.
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.