Lab Science News

Columbia Analytical Services, Inc. has extensive experience testing for low levels of Polycyclic Aromatic Hydrocarbons (PAH) in shellfish. Sensitive and selective techniques were developed over ten years ago and have been refined and improved on a continuing basis. In addition to the analysis for the common parent compounds, levels of the associated alkylated homologs can also be determined.

This analysis is typically performed using Gas Chromatography/Mass Spectrometry (GC/MS) operated in the Selective Ion Monitoring (SIM) mode. Key to the analytical procedure is proper sample preparation, which begins with shucking, compositing (as appropriate to the project plan), and homogenization via mechanical mixing. The preliminary preparation must be performed under clean laboratory conditions to prevent common PAH contamination. Decontamination of sample preparation equipment is performed and monitored closely to assure clean conditions. The sample homogenate is a homogenous slurry when prepared correctly. The homogenization techniques performed by Columbia Analytical have been inspected and approved by various organizations (e.g. US EPA, other federal government and state regulatory agencies, private industries, consultants, etc.) The data results for these projects were subjected to thorough government, public and private scrutiny.

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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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Gas chromatography/mass spectrometry (GC/MS) is the method of choice for the identification of volatile organic compounds (VOCs) in vapor samples (e.g. EPA methods TO-14A and TO-15). As various state and federal agencies more frequently require facilities to address risk-based concentrations, such as the low level preliminary remediation goals (PRGs), they find that the standard method is not able to reach the ultra-low levels needed. To address these requirements, CAS’ Simi Valley, California lab has developed a method using selective ion monitoring (SIM) to measure the compounds. SIM is a sensitivity enhancement technique, where the mass spectrometer is programmed to scan for only those ions that are pertinent to the compounds of interest (2-3 mass ions scanned per compound) while ignoring non-essential ions. The mass spectrometer becomes a highly sensitive compound-specific detector.

The driving force for the lower limits has been health risk assessment activities in the indoor and ambient air arena. The exposure criteria for many compounds are being re-evaluated constantly. A recent symposium sponsored by the Groundwater Resources Association (GRA) on subsurface vapor intrusion to indoor air has recommended that the SIM analytical technique be used. For example, trichloroethene (TCE) will have a reporting limit of 1.0 mg/m3 (0.19 ppbv) using the standard full scan method. In contrast, the reporting limit of 0.05 mg/m3 (0.0093 ppbv) for TCE will be achieved with the SIM technique. This meets or exceeds most risk-based concentration criteria. Lower limits are occasionally requested and are reviewed on a case-by-case basis.

These applications typically require a 6-liter evacuated summa canister equipped with low volume flow controller to collect time-integrated VOC samples. To minimize contamination and ensure against false positive results, it is important that canisters and flow controllers be individually certified down to the reporting limits. For less demanding projects, where full scan reporting limits are adequate, batch certification (one per ten) of canisters is acceptable.

Using GC/MS in the SIM mode is a valuable tool for investigating situations where ultra-low level reporting limits are desired. Compound lists and reporting limits are constantly being reviewed and revised.

1,4-Dioxane has been used for many years as a stabilizing agent in the production of chlorinated solvents to prevent breakdown during manufacturing processes. It is also present in many household products like soaps, shampoos, baby lotion and cosmetics.

Over the past few years 1,4-Dioxane has garnered increased attention due to it’s presence in groundwater at several California locations and because there is little scientific data available on the longterm effects on human health. An additional concern is that traditional remediation technologies used for sites contaminated with chlorinated solvents are ineffective at removing 1,4-Dioxane.1

The traditional method for the analysis of 1,4-Dioxane is EPA method 8260. The high water solubility of 1,4- Dioxane causes poor purging efficiency, resulting in the relatively high reporting limits of 100 μg/L.While there is no current federal drinking water standard or maximum contaminant level, California EPA has led the nation in setting an advisory action level of 3.0 μg/L. Several different approaches have been used to achieve these lower reporting limits for 1,4-Dioxane including salting purge procedures, vacuum distillation, continuous liquid-liquid extraction, isotope dilution and selected ion monitoring.

Two of the primary problems affecting any method targeting 1,4- Dioxane are poor recovery due to high water solubility and volatility loss. Any purge and trap method is unaffected by volatility loss yet has significant problems with high water solubility. Conversely, extraction methods have problems with volatility loss due to the use of heat when continuous liquid-liquid extractors are used and again in the solvent reduction phase of the extraction.

CAS has incorporated a new method that is able to overcome both issues. The extraction procedure is based on EPA Method 3510. A 100 ml sample volume is used with the addition of 20 g NaCl. The sample is spiked with a surrogate standard, 1,4-Dioxane-d8, and extracted with methylene chloride. The extract is then dried and brought to a final volume of 5 ml. The extract is analyzed by GC/ MS running in the selected ion monitoring (SIM) mode with an ATAS Large Volume Injector (LVI). The LVI allows for a 20 μl injection.

Using the modified extraction procedure combined with large volume injection GC/MS SIM techniques, CAS reliably achieves an MRL of 0.1 μg/L. Using 1,4-Dioxane-d8 as a surrogate also ensures the performance of each analysis. For additional information on 1,4- Dioxane call Jeff Grindstaff or Lynda Huckestein at (360) 577-7222.

1.D. Grant Walson, Bruce Tunnicliffe, 1,4-Dioxane– A Little Known Compound, Environmental Science & Engineering, May ’02.