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1720

Thompson et al.:

J

ournal of

AOAC I

nternational

V

ol.

98, N

o.

6, 2015

7500cx from the SLV, a few Agilent 7700x, a PerkinElmer

ELAN DRC-e, and a Thermo X Series 2. On the other hand, it

is of interest to note the excellent RSDs for Mn and Cu across

these laboratories—likely due to the excellent sensitivity of

the ICP/MS for these elements and the effectiveness of the

CRCs in removing background interferences at somewhat

higher mass.

The accuracy of the present method can be further attested

to by comparison to an independent method, the commonly

used ICP-AES, also with microwave digestion. A full SLV was

performed on the SPIFAN matrix set in the authors’ laboratory

using the same microwave oven (CEM MARS 5 with

MARSXpress™ vessels) and two PerkinElmer Optima ICP

instruments. The mean 6-day ICP-AES results were compared

to the mean values from the ICP/MS MLT (similar to those

means in Table 4). The results are shown in Table 8. Again,

we must disregard the numbers for the Adult RTFs because the

ICP-AES data were acquired several months ahead of the MLT

study, and these products had probably physically deteriorated.

The remaining powder products show remarkable agreement

between the two spectroscopies. In general, MS data are higher

than those produced by emission, but seldom is there more

than 6% difference.

Conclusions

The method, as is, meets all SMPRs except for the LOQ of

Fe, Mn, and Cu. There was also substantial evidence presented

to support the accuracy and reproducibility of this method

through comparison to an independent method and through

analyses completed at independent laboratories with different

models of ICP/MS instruments. The data from the SLV and

MLT studies were consistent with each other. Additional

linearity work, spiking at low-levels, increasing sample size,

and/or additional low level standards would be needed to

prove accuracy at the lowest levels for Fe, Cu, and Mn.

Acknowledgments

We thank Andre Szabo for participating as the second

analyst in this SLV. Also, we thank the participants of the

OMA

2011.19

collaborative study that contributed nine-

element data for this report: Fan Xiang, Sudhakar Yadlapalli,

Isabelle Malaviole, Ashutosh Mittal, Michael Gray, Diana

Mould, and Michael Farrow.

References

(1)

Official Methods of Analysis

(2011) AOAC INTERNATIONAL,

Rockville, MD, SMPR 2011.009.

www.eoma.aoac.org

(2)

Official Methods of Analysis

(2014) AOAC INTERNATIONAL,

Rockville, MD, SMPR 2014.004

. www.eoma.aoac.org

(3)

Official Methods of Analysis

(2011) AOAC INTERNATIONAL,

Rockville, MD, Official Method

2011.19

.

www.eoma.aoac.org

(4) Pacquette, L., Szabo, A., & Thompson, J

. (2011) J. AOAC Int . 94 , 1240–1252

(5)

Official Methods of Analysis

(2012) AOAC INTERNATIONAL,

Rockville, MD, Appendix L.

www.eoma.aoac.org

(6) Thompson, J., Pacquette, L., & Brunelle, S. (2015)

J. AOAC Int.

98

, in press

79