Lab Science News

The recent explosion of a drilling rig 50 miles off the Louisiana coast and the subsequent massive oil leak is expected to have substantial effects on the environment. At the current rate, the spill is expected to surpass the 11 million gallons spilled in the Exxon Valdez disaster. Various investigations, monitoring activities, damage assessments, and other related studies will be occurring for many years as a result of this event. From an analytical chemistry standpoint, several relatively specialized procedures will be required to assure that contaminants detected originated from this spill. In addition, a certain amount of standardization between all laboratories performing testing will be necessary to assure comparable data.

The key procedures that will be used for much of the testing are briefly described in the following:

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1,4-Dioxane (dioxane) is a chemical of concern for its potential health effects as a carcinogen and irritant. It is commonly found in personal care products such as detergents, shampoos, body lotions, and cosmetics, and is widely used as an industrial solvent and stabilizer in manufacturing processes (e.g., electronics, metal finishing, fabric cleaning, pharmaceuticals, herbicides, pesticides, antifreeze, paper, etc.). Currently, there are no established limits on the amount of dioxane in personal care products nor is it specifically regulated in manufacturing wastewater streams that may impact the surrounding environment. Manufacturers of personal care products should conduct laboratory analysis to determine the levels of dioxane in their products, and manufacturers using dioxane in their processes should analyze their waste streams for possible dioxane content.

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Naphthalene is a contaminant of concern at former Manufactured Gas Plant (MGP) and other property redevelopment sites across the country. A major component of coal tar waste and a possible human carcinogen (EPA Group C), naphthalene is a chemical that may adversely affect human health at remediation sites. Due to its boiling point and vapor pressure, naphthalene can exhibit both volatile and semi-volatile characteristics; therefore the question can arise as to how to properly measure naphthalene in ambient air.

Two commonly applied methods of measuring vapor phase naphthalene include EPA Method TO-15, which utilizes whole air sampling in passivated stainless steel canisters; and EPA Method TO-13A, which utilizes high volume sorbent based sampling with polyurethane foam/XAD resin cartridges. Analytical differences between these two methods will be discussed, keeping reference to naphthalene’s unique chemical & physical properties.

This case study will present weekly data spanning a twelve month period (December 2006 – December 2007) from co-located EPA Method TO-15 and TO-13A ambient air samples at the perimeter of two MGP cleanup remediation sites. Distinct trends are noted and discussed in this paper when comparing the concentration results from the two methods.

Read the complete naphthalene air sampling case study… (Acrobat PDF)

Chlorine has been used to disinfect water for almost a century due to its ability to kill bacteria and viruses in water. The use of chlorine as a disinfectant has been an effective contribution to public health eliminating plagues such as cholera and typhoid, and reducing the incidence of intestinal illness and other health problems caused by waterborne pathogens such as cryptosporidium. The benefits of disinfection, however, do not come without an effect.

Depending on the disinfection procedure used (chlorination, chloramines, bromine, ozone etc.) and the chemical composition of the water prior to disinfection, many different organic chemical disinfection byproducts can form in drinking water. Trihalomethanes (THMs) are a byproduct of chlorine disinfection and to a lesser degree, disinfection using chloroamines. The THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) are formed when free chlorine combines with organic matter, like decaying vegetation commonly found in lakes and reservoirs. Total Trihalomethanes (TTHM) are regulated by the EPA at a maximum allowable annual average of 80 parts per billion. Some of the THMs are very volatile and will vaporize into air easily, so they may be inhaled while showering, however, the EPA has determined that this exposure is minimal compared to that from consumption. The Levels of THMs formed can vary widely on a number of factors including temperature, amount of chlorine used, season, and amount of plant material in the water, among others.

Some drinking water systems use chloroamines as a residual disinfection agent in place of chlorine. Chloroamine is not as reactive as chlorine and less THMs are formed. However, there are also drawbacks to chloroamine use. Chloroamine may cause nitrification and corrosion and may also increase exposure to other disinfection byproducts, such as N-nitrosodimethylamine (NDMA).

EPA Method 524.2 is used to analyze samples for TTHMs. This method involves concentrating the THMs from a water sample using a technique known as purge and trap. This technique isolates the volatile organic compounds (VOCs) from the water. The VOCs are then desorbed into a gas chromatograph/mass spectrometer (GC/MS) where they are separated, their identity is confirmed, and their concentrations are determined. Standard reporting limits for individual TTH with this method are 0.5 µ/L

The term “vapor intrusion” refers to the migration of volatile chemicals from subsurface contaminated sources into overlying residential or commercial structures. “Historically, it was thought that vapor intrusion was only an issue where the source of the contaminants was very shallow and the magnitude of the contamination was very great. It is now known that the previous assumptions about the mechanisms that could lead to exposure to vapor intrusion were not complete (NYS DEC DER Vapor Intrusion Guidance).” For a growing number of federal, state and local agencies, as well as environmental consultants and laboratories, vapor intrusion could emerge as the next major environmental challenge.

Vapor intrusion is not a new phenomenon— for some environmental experts, it has been recognized as a potential pathway of contamination for almost 20 years. In the late 1980s, the first vapor intrusion studies were carried out to evaluate potential health effects from chronic exposure to volatile organic compounds. Presently, vapor intrusion is of growing concern to the environmental community due to a number of factors, such as increased recognition of it as a potential pathway for exposure and the risks associated with that exposure, as well as the location and the number of potential sites for investigation and remediation. With this increased focus comes ongoing debate regarding the mechanism of the exposure pathway, compliance concentrations of contaminants, identification of sites, sampling approaches, analytical methodology, use and validity of current models, screening approaches, and risk assessment, among other topics.

What this has meant for many laboratories specializing in air analyses is an upward trend in the number of ambient air, indoor air, soil gas and sub-slab samples submitted each year for volatile organic compound (VOC) analyses. The primary compounds of concern are often chlorinated VOCs. Trichloroethene (TCE) and tetrachloroethene (PCE), in particular, are common targets of the investigations due to the health risks associated with these compounds and their breakdown products.

In instances where the project specific objectives of the vapor intrusion investigation call for sampling, several kinds of air samples can be collected: soil vapor, ambient (outdoor) air, indoor air and sub-slab vapor. The timing of the collection, as well as the number, placement and combination of samples will all vary depending on the client-defined sampling protocol, which ultimately relies on local, state or federal requirements.

So, keeping in mind the client’s project-specific objectives and the underlying regulatory requirements, here are some of the factors to be taken into consideration for the analytical portion of a vapor intrusion investigation:

Analytical Method

EPA Method TO-15 is the most frequently requested method for the analysis of VOCs for the range of air samples associated with vapor intrusion investigations. The method uses gas chromatography (GC) to achieve sample separation and a mass spectrometer (MS) for identification and quantitation.

TO-15 was a new method added to the Second Edition of the Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air in January 1999. Although very similar to EPA Method TO-14A, EPA Method TO-15 is larger in scope and better defined for the analysis of VOCs in air and other gaseous matrices than TO-14A (which is a revised and updated version of the former Method TO-14).

Compound List

A wide range of compounds may be analyzed by EPA TO-15 including alkanes, alkenes, aromatics, halogenated VOCs, ketones, esters and some alcohols. Some aldehydes and sulfides may also be evaluated using this method.

EPA TO-15 does not specify a target compound list in the method. As a result, there is some variation among commercial environmental laboratories in the compound lists that are available for VOCs. Target compound lists may include anywhere from 40 to 60 compounds or more, and may provide results in μg/m3, ppbV, or both.

Compound lists can usually be tailored to meet project-specific objectives. This is true especially in the case of indoor air, which typically involves a subset of the laboratory’s standard target compound list.

Method Reporting Limits

Target method reporting limits (MRLs) will vary depending on the data quality objectives of the investigation, which should take into account any state or federal regulatory documents or guidances that may apply.

For soil gas or sub-slab samples, it is usually sufficient to analyze the samples in the normal operating mode of the GC/MS (SCAN), which yields MRLs from sub-parts per billion up to parts per million levels.

For indoor or ambient air analyses, investigators are often considering the potential risk to human health, so they are typically interested in lower MRLs, down to the single digit part per trillion levels. Indoor air and ambient air analyses are frequently performed by GC/MS in Selective Ion Monitoring (SIM) mode to achieve these ultra-low level MRLs.

The risk-based levels for the contaminants of concern are, in many cases, less than the typical or observed background levels in the indoor or outdoor environment, creating a challenge for many vapor intrusion investigations. The best approach for assessing and dealing with this issue continues to be discussed and debated by experts in the field.

Sampling Media

For soil gas determinations, samples may be collected using either passivated stainless steel canisters (such as Summa canisters) or Tedlar bags. Each sampling medium has its advantages and disadvantages, as summarized in the table below.

For soil gas sampling, 1L Summa canisters can offer certain benefits over the larger 6L canisters. They fill faster, reducing time in the field for the investigators. They are smaller and lighter, so they are easier to transport, handle and ship. The smaller volume reduces the likelihood of ambient air intrusion, especially when sampling more densely packed soils. The trade off is that a smaller sample portion can be withdrawn from the canister for the analysis, which results in higher MRLs than those achievable from samples collected in a larger canister, typically 3 to 5 times higher.

For indoor air or ambient air sampling, 6L Summa canisters are the recommended sampling medium. Canisters may be either batch certified clean or individually certified clean—the selection depends, again, on the data quality objectives of the project and on any regulatory specifications. In situations where it may be valuable to have documentation for every canister, (e.g. potential litigation, risk assessment), then individual certification can be requested. In either case, the canisters will be cleaned and certified below the target MRLs.

Columbia Analytical’s Air Quality Laboratory has extensive experience performing analyses of indoor and ambient air, as well as sub-slab and soil gas samples. Specializing in the analysis of volatile and semi-volatile organic compounds, sulfur compounds and other hazardous substances in a wide variety of air and vapor matrices since 1988, the lab has performed tens of thousands of analyses from its southern California location near Los Angeles, and it successfully serves clients in all 50 states and around the globe.

Columbia Analytical recently conducted a field evaluation of Odor Scan, a suite of methods that has been designed to address compounds that have very low odor thresholds and are irritating at low levels. The suite consists of sampling and analytical methods for carboxylic acids (volatile organic/fatty acids), amines, reduced sulfur compounds and odorous volatile organic compounds (VOCs) such as microbial volatile organic compounds (MVOCs), and high molecular weight aldehydes and alcohols. Two of these methods (ie. amines, carboxylic acids) were developed and validated by Columbia Analytical.

The study was conducted to evaluate the new methods under field conditions and to collect data to profi le the airborne contaminants and odors associated with a composting facility. Due to the wide range of compounds anticipated and the fact that some analyte overlap exists among the methods, this sampling event was also used to compare sampling and analytical methods and sampling media.

The facility composts a variety of materials including green waste, cow manure, construction materials (e.g., sheet rock), and chicken and fish waste. The compost was piled in seven uncovered windrows that were located outdoors on a concrete slab. At this facility, the composting process takes approximately six to seven weeks from the time the material is received until it is ready for screening. Heavy equipment called a SCAT is used to turn the material in the windrows, which helps aerate the product, an important component of the composting process. The final compost product generated is sold for landscaping.

Air samples were collected at the property’s fence line, on top of compost piles and on the SCAT used to turn the compost piles. Sampling media, fl ow rates and analytical methodologies utilized are summarized in Table 1. Calibrated personal sampling pumps were used to collect the solid sorbent samples. For some target compounds (e.g., VOCs, reduced sulfurs), collocated samples were collected using more than one media type.

The analysis of samples for tentatively identifi ed compounds (TICs) by EPA TO-15 and NIOSH 2549 was achieved by comparing the mass spectra of the selected peaks with those from the NIST library, which contains spectra from more than 120,000 compounds. The concentrations of TICs were estimated by comparing the peak area of the compound with that of the nearest internal standard. As the compounds present at the highest concentrations are often not the odorous ones, the analysis was not limited to the 15 largest peaks, as is often the case with these methods. Instead, for method validation purposes, all those peaks with suffi cient response to permit identifi cation of the mass spectra were selected. In some cases, it was not possible to locate the peaks buried in the complex matrix. For some compounds (e.g., carboxylic acids), it was diffi cult to accurately estimate peak area because of the wedge shape of the peaks produced using the EPA and NIOSH methods. The Columbia Analytical Carboxylic Acid method resolves this problem.

Approximately 350 different compounds were identifi ed during the study, including many of the reduced sulfur, carboxylic acid and amine compounds on the OdorScan target lists as well as a diverse mixture of VOCs. Trimethylamine was the predominant amine, while acetic, butyric, propionic and isovaleric acids were the principal carboxylic acids found in many of the samples. When the two VOC methods (NIOSH 2549, EPA TO-15) were compared, more substances were detected in the samples collected on thermal desorption tubes (265 compounds) than in Silco canisters (219 compounds). The types of VOCs identifi ed included higher molecular weight alcohols, aldehydes and ketones (e.g., 2-heptanol, decanal, 2-octanone), terpenes (α & β-pinene, d-limonene, carene), furans, phenols and cresols. Microbial volatile organic compounds were also detected in several of the samples.

As expected, the highest levels were observed in the samples collected near the source: at the top of the compost piles and during the turning of the compost. Samples collected from the newer piles tended to be more complex with respect to the VOCs and reduced sulfur compounds

detected. Based on comparisons with reported odor thresholds, butyric acid, valeric acid, isovaleric acid, acetic acid, propionoic acid, isobutyric acid, dimethyl disulfi de, acetaldehyde, decanal, nonanal, benzaldehyde and, p-cresol were likely contributors to the odor detected at the edge of the property. The preponderance of carboxylic acids present at levels above their odor thresholds was consistent with the sweaty/fecal/sour odor detected.

Although the NIOSH 2549 Method detected the greatest number of compounds, it did not appear to be an effective technique for identifying the presence of amines. The method also underestimated carboxylic acid levels. This study suggests that even a fairly comprehensive method, such as NIOSH 2549, does not effectively capture the full range of compounds that may be contributing to a complex contaminant matrix. The use of the four different methods that comprise OdorScan was a better choice for characterizing the airborne contaminants associated with this odorous source.

Read more about Odor Investigations…

Read more about Odor Compounds at a Compost Facility (PDF)…

Read more about Odor Testing…

The Department of Antiquities Conservation of the J. Paul Getty Museum recently requested assistance from CAS’ Simi Valley Air Quality Laboratory to sample and analyze the atmosphere surrounding a second century Egyptian mummy. About six years ago, the mummy was sealed in a case containing ambient air. The museum wished to determine the volatile and semivolatile organic compounds off-gassing from the mummy. One purpose of the study was to determine the impact of off-gassing on other artifacts that were to be displayed with it.

Compounds of interest included low molecular weight organic acids, volatile organic chemicals, and the semivolatile compound, guaiacol. Guaiacol is a component of cedar oil and one of the embalming fluids used by the Egyptians.The other chemicals were associated with previous restoration activities with the mummy.

In order to collect the samples, two holes were drilled in the case housing the mummy. Sampling ports consisting of Teflon tubing (1/4” OD) and a ferrule and female Swagelok fitting were installed in the holes. The ports were sealed off at the time of installation and only opened during sampling periods.

Two sampling and analytical methods were used to address the compounds of interest. Volatile organic compounds were sampled in evacuated passivated stainless steel canisters (SUMMA-like) and then analyzed for tentatively identified compounds (TICs) by gas chromatography/ mass spectrometry (GC/MS) following US EPA Method TO-15. This technique involves identifying the most predominant compounds by Jeanette Campbell - Simi Valley, CA in the sample by comparing their mass spectra with those from the NIST library, which contains mass spectra from more than 120,000 compounds. Heavier compounds were sampled on Tenax TA tubes and then thermally desorbed and analyzed by GC/MS following EPA Method TO-17. These samples were analyzed for guaiacol and other TICs, including acetic acid.

Compounds of both biogenic (e.g., isobutyric acid) and synthetic origin were identified in the samples (see Figure 1 on page 3). Acetaldehyde, 3-methylbutanal, pentanal, furfural and methyl methacrylate were present above their odor threshholds. Several of these compounds had an “odor character,” that might have contributed to the “characteristic mummy odor” described by one of Getty’s researchers.

An important outcome of this project was the side-by-side comparison of the efficacy of two sampling methodologies that are frequently used to evaluate organic compounds in indoor air investigations. Neither media type collected the full range of compounds of interest. Lighter compounds were only detected in the SUMMA-like canister sample. In contrast, heavier, higher boiling point compounds were only identified in the samples collected on the Tenax sorbent tube. Midrange compounds (e.g., boiling points of 70oC to 240oC) were detected using both sampling media and showed similar quantitative and qualitative results.

Although boiling point appeared to be the primary determinant of the compounds that were collected by the two types of media, other properties (vapor pressure, polarity, lability) may also have had an impact. For example, the labile compound, isobutyric acid, was only detected in the solid sorbent samples even though its boiling point (155o C) is in the more volatile range, which may be collected by SUMMA canisters.

The Mummy project presented the laboratory with a unique opportunity to evaluate an environment containing a wide range of compounds. The results of this project suggest that for indoor air investigations, the use of multiple sampling media may generate more meaningful data than reliance on a single type.

CAS would like to thank Cecily Grzywacz, Scientist in the Science Department of the Getty Conservation Institute and Marie Svoboda, Associate Conservator of Antiquities at the J. Paul Getty Museum for allowing us to present the results of their project.