Lab Science News - Science, chemistry and environmental news from laboratory experts

Archive for February, 2005

Hexavalent Chromium in Aqueous Samples Containing Color and Chemical Interferences

Friday, February 4th, 2005

Hexavalent-Chromium-in-Aqueous-Samples-Containing-Color-and-Chemical-InterferencesBackground
Today there are two common colorimetric techniques using a Diphenylcarbazide (DPC) solution for determining Hexavalent Chromium (Cr+6) in RCRA site water samples. EPA Method 7196, a colormetric method, analyzes the untreated or filtered sample as is. EPA Method 7199, an ion chromatographic method, separates the Cr+6 ion from interferences and is then followed by post column reaction with DPC. Therefore, colored matrices or matrices containing chemical interferences may be better analyzed by ion chromatography as shown in the following example.

(more…)

Odor Scan Evaluation of a Composting Facility

Friday, February 4th, 2005

Odor Scan Evaluation of a Composting FacilityColumbia 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 profile 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.

(more…)

Highly Anticipated Perchlorate Report Released

Friday, February 4th, 2005

Highly Anticipated Perchlorate Report ReleasedOn Tuesday, January 11, 2005 the Committee to Access the Health Implications of Perchlorate Ingestion, convened by the National Research Council at the request of the EPA, DOD, NASA, and the DOE, released their report on the adverse health effects of perchlorate ingestion from clinical, toxicological and public health perspectives. The report also evaluated relevant scientific literature and key findings of the EPA’s 2002 draft risk assessment document on perchlorate. The full report can be found online here.

The committee noted that a no observed-effect level (NOEL) or lowest observed-adverse-effect level (LOAEL) identified from a critical study, is used as the basis for establishing a reference dose for daily oral exposures. The committee decided to use a NOEL rather than a LOAEL as the basis for perchlorate risk assessment. They based their reference daily dose on the identified critical study done by Greer, et al (2002)1 in which healthy men and women were given doses of perchlorate of 0.007 to 0.5 mg/Kg body weight per day for 14 days. In this study, the NOEL was found to be 0.007 mg/Kg/day. Using this amount and applying an uncertainty factor of 10 to protect the most sensitive population (identifi ed as pregnant women who may have hypothyroidism or iodide deficiency), the committee recommended a reference daily dose of perchlorate of 0.0007 mg/Kg of body weight per day from all sources. The EPA’s draft reference daily dose from the 2002 risk assessment was 0.00003 mg/Kg per day. The committee also noted that additional studies are needed, especially long-term, chronic exposure as well as clinical, mechanistic and epidemiological studies.

(more…)