Ask the Expert Question:
How do you overcome the redox interferences of 7196A/3060A?
Expert Response:
When using Methods 3060A/7196A it is common to also test for several other general chemistry parameters that relate to the reduction / oxidation conditions present in site soil samples. These auxiliary results are then used to help interpret the Cr(VI) results. Including client specified matrix spike samples is also an excellent way to assess matrix interferences.
In reducing soil conditions Cr(VI) is converted to Cr(III). This is a common remediation process. However, in some instances the reducing agent is not evenly distributed and unreacted pockets of Cr(VI) remain. When the sample is brought to the lab and run through the 3060A alkaline leaching process, both the reducing agent and the Cr(VI) are solubilized and complete the reaction. It makes it look as if there was no Cr(VI) in the sample, even though there really was. Matrix spike recoveries usually alert the data user when this situation has occurred. Using the method of standard additions (MSA) with Methods 3060A/7196A to calculate the Cr(VI) concentration can compensate for moderate reduction/oxidation interferences. Both the auxiliary general chemistry tests and MSA options are available at TestAmerica.
Colorimetric interferences are also possible in 7196A. When these occur, the ion chromatographic Method 7199 is the best and most cost effective way to minimize these interferences. This is about 2-4X more expensive than method 7196A. Method 7199 doesn’t resolve the reduction / oxidation interferences described above.
Method 6800 is capable of resolving most reduction / oxidation interferences as well as the colorimetric interferences that Method 7196A experiences. Method 6800 testing is about 10X more expensive than Method 7199. It is usually quoted by project.
View Dr. Mark Bruce's expert profile
Monday, March 21, 2011
Tuesday, March 15, 2011
Benefits and Alternatives of the Various Methods for Metals Speciation for Chromium in Soils
Ask the Expert Question:Can you summarize the benefits and alternatives of the various methods for metals speciation for chromium in soils?
Expert Repsonse:
Method 3060A is the primary sample preparation method used to extract the hexavalent chromium (Cr(VI)) from a soil matrix. This sample preparation method must then be followed with an analysis method to determine the Cr(VI) concentration. There are three analytical technique options.
The most common is colorimetry as described in Method 7196A. This test is widely available and low cost. It can suffer from color based and reduction / oxidation chemistry (redox) matrix interferences.
Ion chromatography with colorimetric detection is used in Method 7199. Method 7199 is available from many labs, though it is less common than 7196A and is a bit more expensive. This method resists the color based interferences, but is still affected by the redox chemistry of the soil matrix.
The most sophisticated technique uses ion chromatography coupled with ICP/MS detection and uses isotopically labeled chromium species. This is described in Method 6800. There are only a few labs in the United States with this capability, TestAmerica being one of them. It is much more expensive than either 7196A or 7199. This method compensates for both color based and redox interferences in most samples.
All of the Cr(VI) analysis options are available from TestAmerica. For additional information on these methods, please submit at question at this link: http://www.testamericainc.com/contactus/contactform.aspx.
View Dr. Mark Bruce's expert profile
Expert Repsonse:
Method 3060A is the primary sample preparation method used to extract the hexavalent chromium (Cr(VI)) from a soil matrix. This sample preparation method must then be followed with an analysis method to determine the Cr(VI) concentration. There are three analytical technique options.
The most common is colorimetry as described in Method 7196A. This test is widely available and low cost. It can suffer from color based and reduction / oxidation chemistry (redox) matrix interferences.
Ion chromatography with colorimetric detection is used in Method 7199. Method 7199 is available from many labs, though it is less common than 7196A and is a bit more expensive. This method resists the color based interferences, but is still affected by the redox chemistry of the soil matrix.
The most sophisticated technique uses ion chromatography coupled with ICP/MS detection and uses isotopically labeled chromium species. This is described in Method 6800. There are only a few labs in the United States with this capability, TestAmerica being one of them. It is much more expensive than either 7196A or 7199. This method compensates for both color based and redox interferences in most samples.
All of the Cr(VI) analysis options are available from TestAmerica. For additional information on these methods, please submit at question at this link: http://www.testamericainc.com/contactus/contactform.aspx.
View Dr. Mark Bruce's expert profile
Monday, March 7, 2011
Ask the Expert Webinar Series launched!
The first webinar is March 24th and will feature Dr. Mark Bruce, Technical Director at the TestAmerica North Canton Laboratory, presenting on Incremental Sampling Methodologies (ISM). Future webinar topics will include endocrine disruptors, chemical issues related to natural gas fracking, and speciated metals, among others.
“TestAmerica has a long tradition of being the technical leaders within the environmental laboratory industry. We are very excited to expand our Ask the Experts program by sharing their expertise with the environmental community. The webinar series will mark a new chapter for TestAmerica as the LEADER in Environmental Testing,” added Rachel Brydon Jannetta, President and CEO.
Go to TestAmerica’s website to learn more about the upcoming webinars and register.
Monday, February 28, 2011
Sulfur in Oil Concentration
Ask the Expert Question:
We have had a need to analyze diesel fuel samples for sulfur and heat content analysis utilizing SW-846 Method 5050 and 9056 as the analytical procedure used to determine sulfate percent. Some of the samples may be analyzed for air permit compliance. The permits require us to have the sulfur content analyzed by ASTM D4294 or equivalent method.
I have read through the documentation on ASTM D4294, SW-846 Method 5050, and SW-846 Method 9056. It appears to me that the methods get to the same end point - sulfur content. However, I would like a second opinion from one of your content experts that confirms what I have concluded.
Experts Response:
The ASTM D4294 (energy dispersive X ray fluorescence technique) is widely used for measurement of sulfur in oils.
The EPA Methods 5050 and 9056 (determination of sulfate ion concentration) is a complete oxidation using a bomb calorimeter followed by analysis of the resulting sulfate. This technique is used for sulfur in oil and waste products and has been used for decades. This is a highly reliable method for determination of sulfur in oils.
Both techniques should give similar results.
View Dr. Charlie Carter's Experts profile
We have had a need to analyze diesel fuel samples for sulfur and heat content analysis utilizing SW-846 Method 5050 and 9056 as the analytical procedure used to determine sulfate percent. Some of the samples may be analyzed for air permit compliance. The permits require us to have the sulfur content analyzed by ASTM D4294 or equivalent method.
I have read through the documentation on ASTM D4294, SW-846 Method 5050, and SW-846 Method 9056. It appears to me that the methods get to the same end point - sulfur content. However, I would like a second opinion from one of your content experts that confirms what I have concluded.
Experts Response:
The ASTM D4294 (energy dispersive X ray fluorescence technique) is widely used for measurement of sulfur in oils.
The EPA Methods 5050 and 9056 (determination of sulfate ion concentration) is a complete oxidation using a bomb calorimeter followed by analysis of the resulting sulfate. This technique is used for sulfur in oil and waste products and has been used for decades. This is a highly reliable method for determination of sulfur in oils.
Both techniques should give similar results.
View Dr. Charlie Carter's Experts profile
Monday, February 21, 2011
Source Types for Benzene Concentration Without Similar Elevated TEX Concentrations
Ask the Expert Question:
At a remediation site we are working on, there is a monitoring well that had soil samples taken during the drilling process and analyzed for BTEX. All concentrations were below 1 part per million. However, the groundwater analysis is presenting an extremely elevated level of benzene with comparable levels of the TEX components. Other wells in the area are either non-detect or have low concentrations for benzene. The data has been verified and is accurate.
We do not understand the elevated Benzene constituent. What type of source would yield such a high Benzene concentration without similar elevated TEX concentrations?
Experts Response:
When benzene is present in environmental samples it is typically an indication of contamination by gasoline or some type of hydrocarbon based fuel. In those cases, however, other aromatics such as toluene, ethyl benzene, and xylenes are present along with numerous alkanes and alkenes. In this sample, the volatiles analysis did not indicate the presence of the other gasoline constituents that we would normally expect.
Benzene was used in various commercial products up until the late 1970’s. These included Liquid Wrench, model cement, paint strippers, rubber cements, and degreasers. It was available commercially in hardware stores for various applications, much like mineral spirits and turpentine are today. Given the presence of benzene in this sample and the absence of other gasoline related constituents, it seems likely that the contamination resulted from a relatively pure source of benzene used for one of these applications.
View Dr. Charlie Carter's Experts profile
At a remediation site we are working on, there is a monitoring well that had soil samples taken during the drilling process and analyzed for BTEX. All concentrations were below 1 part per million. However, the groundwater analysis is presenting an extremely elevated level of benzene with comparable levels of the TEX components. Other wells in the area are either non-detect or have low concentrations for benzene. The data has been verified and is accurate.
We do not understand the elevated Benzene constituent. What type of source would yield such a high Benzene concentration without similar elevated TEX concentrations?
Experts Response:
When benzene is present in environmental samples it is typically an indication of contamination by gasoline or some type of hydrocarbon based fuel. In those cases, however, other aromatics such as toluene, ethyl benzene, and xylenes are present along with numerous alkanes and alkenes. In this sample, the volatiles analysis did not indicate the presence of the other gasoline constituents that we would normally expect.
Benzene was used in various commercial products up until the late 1970’s. These included Liquid Wrench, model cement, paint strippers, rubber cements, and degreasers. It was available commercially in hardware stores for various applications, much like mineral spirits and turpentine are today. Given the presence of benzene in this sample and the absence of other gasoline related constituents, it seems likely that the contamination resulted from a relatively pure source of benzene used for one of these applications.
View Dr. Charlie Carter's Experts profile
Monday, February 14, 2011
Volatile versus a Semi-Volatile Compounds
Ask the Expert Question:
What makes a compound a volatile versus a semi-volatile?
Expert Response:
There is no hard and fast rule to determine what is called a volatile compound and what is called semi-volatile. There are a variety of chemical characteristics that influence volatility, but for the most part the definitions that are used in environmental analysis are operational definitions.
The operational definition is whether a compound will purge from aqueous solution in a purge and trap device. If a compound will do so at a high enough rate to be detected and quantified, then it is considered to be volatile. If an analyte is only found in a semi-volatile analysis and is not present in the volatiles analysis, then almost by definition it is not volatile.
There are also, however, some physical chemical characteristics of volatile compounds. The key characteristics are (1) vapor pressure or boiling point, and (2) aqueous solubility. As the vapor pressure increases, a compound’s volatility increases. As its aqueous solubility decreases, it also becomes more volatile from an aqueous solution.
For example, 1,2,4-trichlorobenzene is about the highest boiling compound routinely included in a volatiles analysis. Its boiling point is listed as 214.4 degrees Celsius, and it is quite water insoluble. Nitrobenzene’s boiling point is 210.9 degrees Celsius, but it is more soluble in water due to the polar nature of the nitro group. It does not purge with sufficient efficiency, so it is not considered a volatile.
View Dr. Charlie Carter Experts profile
What makes a compound a volatile versus a semi-volatile?
Expert Response:
There is no hard and fast rule to determine what is called a volatile compound and what is called semi-volatile. There are a variety of chemical characteristics that influence volatility, but for the most part the definitions that are used in environmental analysis are operational definitions.
The operational definition is whether a compound will purge from aqueous solution in a purge and trap device. If a compound will do so at a high enough rate to be detected and quantified, then it is considered to be volatile. If an analyte is only found in a semi-volatile analysis and is not present in the volatiles analysis, then almost by definition it is not volatile.
There are also, however, some physical chemical characteristics of volatile compounds. The key characteristics are (1) vapor pressure or boiling point, and (2) aqueous solubility. As the vapor pressure increases, a compound’s volatility increases. As its aqueous solubility decreases, it also becomes more volatile from an aqueous solution.
For example, 1,2,4-trichlorobenzene is about the highest boiling compound routinely included in a volatiles analysis. Its boiling point is listed as 214.4 degrees Celsius, and it is quite water insoluble. Nitrobenzene’s boiling point is 210.9 degrees Celsius, but it is more soluble in water due to the polar nature of the nitro group. It does not purge with sufficient efficiency, so it is not considered a volatile.
View Dr. Charlie Carter Experts profile
Wednesday, February 9, 2011
Dust Sampling Methods and Equipment
Ask the Expert Question:
There are abandoned mine land sites in our area that are often used for recreational activities. These activities generate a great deal of dust. The sediments and mine wastes in these areas are potentially contaminated with heavy metals and could put people using these public areas at risk. Can you provide any information on methods to sample the dust? Also, where can I obtain the equipment to do the sampling?
Experts Response:
There are several considerations for deciding upon how to approach monitoring the dust.
The first consideration is: what will you compare your data to with regard to health standards or risk criteria? The answer will help to define how you will collect the samples. For example, it may make sense to compare your results to the National Air Quality Standard for the particular heavy metals contamination present, and/or the PM10 standard for Total Particulate. Some counties in the US even have their own ambient air quality criteria.
Your choice of criteria will dictate how the samples should be collected; the detection levels required and for what time period the samples must be collected. As an example, the National Air Quality Standard for Lead requires that a sample be collected for a 24 hour period.
A second consideration is: do you have a source of electrical power, or will it be necessary to use sampling equipment that is battery powered? Battery powered equipment may pose a problem if your sampling period must cover 24 hours.
TestAmerica does have air sampling pumps available for clients depending upon your sampling criteria. Click here to contact our expert, Mike McGee to inquire about the equipment and methods available.
View Mike McGee's Experts profile
There are abandoned mine land sites in our area that are often used for recreational activities. These activities generate a great deal of dust. The sediments and mine wastes in these areas are potentially contaminated with heavy metals and could put people using these public areas at risk. Can you provide any information on methods to sample the dust? Also, where can I obtain the equipment to do the sampling?
Experts Response:
There are several considerations for deciding upon how to approach monitoring the dust.
The first consideration is: what will you compare your data to with regard to health standards or risk criteria? The answer will help to define how you will collect the samples. For example, it may make sense to compare your results to the National Air Quality Standard for the particular heavy metals contamination present, and/or the PM10 standard for Total Particulate. Some counties in the US even have their own ambient air quality criteria.
Your choice of criteria will dictate how the samples should be collected; the detection levels required and for what time period the samples must be collected. As an example, the National Air Quality Standard for Lead requires that a sample be collected for a 24 hour period.
A second consideration is: do you have a source of electrical power, or will it be necessary to use sampling equipment that is battery powered? Battery powered equipment may pose a problem if your sampling period must cover 24 hours.
TestAmerica does have air sampling pumps available for clients depending upon your sampling criteria. Click here to contact our expert, Mike McGee to inquire about the equipment and methods available.
View Mike McGee's Experts profile
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