Determination of perchlorate in infant formula by isotope dilution ion chromatography/tandem mass spectrometry

Figures & data

Table 1. Comparison of differences in extraction efficiency between solution A and B.

		Perchlorate peak area
Extraction solution	Isotope	Blank spike^a	Formula pre-extraction spike^a	Formula post-extraction spike^a	Matrix effect recovery (%)^b	Absolute recovery (%)^c
4:1 Acetonitrile + 1% acetic acid (solution A)	Cl^16O4	2213	1166	2083	94.1	55.9
	Cl^18O4	12529	6419	11756	93.8	54.5
4:1 Methanol + 1% acetic acid (solution B)	Cl^16O4	2472	1823	2281	92.3	79.9
	Cl^18O4	13742	9473	12592	91.6	75.2
Notes: ^aSpike 1.0 µg l^−1 native + 6.0 µg l^−1 InStd.
^bMatrix effect recovery = peak areapost-extraction spike/peak areablank spike.
^cAbsolute recovery = peak areapre-extraction spike/peak areapost-extraction spike.

Figure 1. Typical MRM mass chromatograms of perchlorate analysis by ID IC-MS/MS.

Table 2. Accuracy and precision of the method.

			Measured concentration (µg l^−1)
Sample type	Spike level	Spiked concentration (µg l^−1)	1	2	3	4	Average	Accuracy (recovery, %)	Precision (coefficient of variation, %)
Liquid formula	1	0.40	0.36	0.46	0.44	0.34	0.40	100	15
	2	10.0	9.95	9.89	9.68	10.1	9.92	99	2.0
	3	50.0	49.7	48.9	50.2	50.8	49.9	100	1.7
Powdered formula	1	2.00	1.99	1.81	1.94	1.81	1.88	94	4.9
	2	10.0	9.37	10.4	9.93	9.47	9.78	98	4.7
	3	50.0	49.8	48.6	49.0	49.9	49.3	99	1.3

Table 3. Summary of perchlorate concentrations in 39 infant formula samples.

Sample ID	Perchlorate in sample as sold (ng g^−1)	Perchlorate in serving solution (µg l^−1)	Type	Base
1	3.10	0.47	Powder	Soy
2	<LOQ	<LOQ	Powder	Milk
3	8.58	1.20	Powder	Milk
4	1.68	0.25	Powder	Soy
5	12.0	1.68	Powder	Milk
6	6.80	1.02	Powder	Soy
7	8.76	1.23	Powder	Milk
8	8.47	1.27	Powder	Soy
9	10.2	1.63	Powder	Milk
10	64.5	13.5	Powder	Milk
11	38.9	8.17	Powder	Milk
12	26.4	3.96	Powder	Milk
13	13.1	1.96	Powder	Milk
14	6.04	0.91	Powder	Milk
15	<LOQ	<LOQ	Powder	Milk
16	1.38	0.21	Powder	Soy
17	5.83	0.88	Powder	Milk
18	1.37	0.21	Powder	Soy
19	54.7	11.5	Powder	Milk
20	0.81	0.81	Liquid^a	Milk
21	4.17	2.09	Liquid^b	Milk
22	1.05	0.52	Liquid^b	Milk
23	1.50	0.75	Liquid^b	Milk
24	0.82	0.41	Liquid^b	Soy
25	3.16	1.58	Liquid^b	Milk
26	0.74	0.37	Liquid^b	Soy
27	7.17	3.56	Liquid^b	Milk
28	2.30	1.15	Liquid^b	Milk
29	4.23	2.12	Liquid^b	Milk
30	0.85	0.42	Liquid^b	Milk
31	0.99	0.49	Liquid^b	Soy
32	3.36	1.68	Liquid^b	Milk
33	1.54	1.54	Liquid	Milk
34	5.97	2.98	Liquid^b	Milk
35	1.39	1.39	Liquid^a	Milk
36	1.46	1.46	Liquid^a	Milk
37	5.50	2.75	Liquid^b	Milk
38	4.15	2.08	Liquid^b	Milk
39	3.56	3.56	Liquid^a	Milk
Notes: ^aReady to use.
^bConcentrated.

Table 4. Percentile distribution of perchlorate concentrations (µg l⁻¹) in the 39 infant formula samples.

20th	30th	40th	50th	60th	70th	80th	90th	95th	Maximum
0.44	0.77	1.05	1.27	1.57	1.85	2.37	3.64	8.50	13.5

Table 5. Comparison in quantifications of perchlorate between the standard addition (SA) and isotope dilution methods.

	Perchlorate concentration (µg l^−1)
Sample	SA	ID	Deviation (%)
10	16.6	13.5	18.6
11	9.74	9.72	0.20
19	13.7	11.5	16.1
7	1.32	1.23	7.57
27	3.62	3.56	1.76