Human urine certified reference material for arsenic speciation

Background: Chemical speciation analysis is essential for the biological mo nitoring of inorganic arsenic exposure using urine as indicator medium. The re is increasing demand for a certified reference material (CRM) of urine m atrix for arsenic speciation. Methods: Urine (10 L) was collected from non-occupationally exposed Japanes e males. We prepared 954 bottles of urine, each containing similar to 10 mt , after filtering and blending the urine stock. The urine in each bottle wa s freeze-dried. Between-bottle homogeneity was confirmed by measuring the c oncentrations of selected minor and trace elements in the material and subs equent statistical analysis. Certification was based on a collaborative ana lysis involving 15 laboratories. Results: Certified values were determined for arsenobetaine (0.069 +/- 0.01 2 mg As/L), dimethylarsinic acid (0.036 +/- 0.009 mg Asn), and total arseni c (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 c ollaborating laboratories. Reference values are given for copper (0.010 mg/ L) and lead (0.0011 mg/L), based on definitive analysis at the National Ins titute for Environmental Studies (NIES). Conclusions: The present CRM, NIES CRM No. 18 Human Urine, is the first hum an urine CRM for arsenic speciation and will be of value for analytical qua lity assurance of the biological monitoring of arsenic exposure. (C) 2000 A merican Association for Clinical Chemistry.