High-Accuracy Determination of Potassium and Selenium in Human Serum by Two-Step Isotope Dilution ICPMS

Table 3

Analysis of standard reference material by two-way ID-ICPMS.

	K (mg kg^−1)				Se (μg kg^−1)
	NIST956D			GBW09152	NIST909C	GBW09152
	Level 1	Level 2	Level 3
Test 1	218.43	140.78	62.52	166.7	116.3	76.3
Test 2	219.66	141.21	62.39	168.0	115.9	76.5
Test 3	219.74	141.69	61.04	167.6	115.8	75.2
Avg	219.28	141.23	61.98	167.43	116.00	76.00
Certified values	219.87 ± 1.86	142.47 ± 1.37	61.50 ± 0.53	168.3 ± 3.4	115.9 ± 3.2	75.7 ± 1.6
Bias (%)	0.3%	0.9%	−0.8%	0.5%	−0.1%	−0.4%