In the NHANES studies seven arsenic species are measured in urine, which is considered the best proxy for recent (one- to two-day) arsenic exposure. Arsenic in drinking water, which is limited to 0.01 mg/L by the Environmental Protection Agency (EPA), is in the most toxic inorganic forms of arsenite (AsIII) and arsenate (AsV). Food intake is the greatest source of dietary exposure (about 25 to 50 µg per day); however arsenic in foods such as fish and shellfish is typically in organic forms such as arsenobetaine (AB), arsenocholine (AC), and arsenosugars that are essentially nontoxic. In addition to the species associated with dietary exposure (AsIII, AsV, AB, and AC), the seven arsenic species measured in NHANES also include the metabolites of inorganic arsenic: monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and trimethylarsine oxide (TMAO).
With certified values for all seven species at key levels, SRM 2669 is the first reference material to contain primary arsenic species of dietary exposure and their metabolites in one material, which makes it most suited as a quality assurance material for arsenic exposure measurements. The reference material is the first to contain As(III) and As(V) species, the most toxic and most important for assessment of arsenic poisoning yet most difficult to stabilize. Because the matrix of the reference material is natural rather than processed (e.g., freeze dried), the product is better suited for the intended purpose of validating the accuracy of methods for urine analysis.
Additional Technical Details:
NIST and CDC staff jointly produced SRM 2669 at the CDC facility in Atlanta, GA. To ensure the stability of the SRM, candidate urine materials were sparged with nitrogen for removal of oxygen. Next, the SRM vials were filled under nitrogen in glove boxes. The SRM was packaged in sealed, gas-impermeable Mylar bags that contain an oxygen absorber. The finished products were stored in –80 ºC freezers.
Because primary references are not available for all of these analytes, we developed our calibration standards from commercially available arsenic compounds by subtracting impurity species (measured by liquid chromatography inductively coupled plasma, LC-ICPMS) from total arsenic (measured by instrumental neutron activation analysis, INAA). SRM 2669 was certified using data provided by NIST, CDC (Atlanta), and Rutgers University.
Start Date:June 1, 2006
End Date:June, 2008
Lead Organizational Unit:mml
Centers for Disease Control and Prevention (CDC)
Therese A. Butler
Related Programs and Projects:
Measurements and Standards for Contaminants in Biological (Human) Materials