TABLE 2.

NIST SRMs for urine with values for iodine¹

		L1			L2
SRM	Description	Iodine, μg/L	Uncertainty,2 μg/L	Unit of issue	Iodine, μg/L	Uncertainty,2 μg/L	Unit of issue	Date of issue
2670a	Toxic elements in urine	88.23	1.1	2 bottles	88.23	1.1	2 bottles	August 2003
3668	Mercury, perchlorate, and iodide in frozen human urine	142.74	1.6	5 × 1.5 mL	279.04	3.9	5 × 1.5 mL	November 2011

¹L1, Level 1; L2, Level 2; NIST, National Institute of Standards and Technology; SRM, Standard Reference Material.

²Expanded uncertainty about the mean. Refer to SRM Certificate of Analysis for details.

³Iodine mass concentration after reconstitution with 20.00 mL water. The reference material consists of a blank matrix (Level 1) and a fortified matrix (Level 2). However, the fortified matrix does not contain added iodine and thus the iodine mass concentration is identical in Levels 1 and 2.

⁴Iodine mass concentration.