Human urine certified reference material for arsenic speciation.

BACKGROUND Chemical speciation analysis is essential for the biological monitoring of inorganic arsenic exposure using urine as indicator medium. There is increasing demand for a certified reference material (CRM) of urine matrix for arsenic speciation. METHODS Urine (10 L) was collected from non-occupationally exposed Japanese males. We prepared 954 bottles of urine, each containing approximately 10 mL, after filtering and blending the urine stock. The urine in each bottle was freeze-dried. Between-bottle homogeneity was confirmed by measuring the concentrations of selected minor and trace elements in the material and subsequent statistical analysis. Certification was based on a collaborative analysis involving 15 laboratories. RESULTS Certified values were determined for arsenobetaine (0.069+/-0.012 mg As/L), dimethylarsinic acid (0.036+/-0.009 mg As/L), and total arsenic (0.134+/-0.011 mg/L) as well as for total selenium (0.059+/-0.005 mg/L) and zinc (0.62+/-0.05 mg/L), based on the analytical values from the collaborating laboratories. Reference values are given for copper (0.010 mg/L) and lead (0.0011 mg/L), based on definitive analysis at the National Institute for Environmental Studies (NIES). CONCLUSIONS The present CRM, NIES CRM No. 18 Human Urine, is the first human urine CRM for arsenic speciation and will be of value for analytical quality assurance of the biological monitoring of arsenic exposure.