AOAC Final Action Methods in 2017

where x = analyte concentration (ng/g); y = analyte-to-ISTD intensity ratio, which is the measured count of each analyte’s standard solution data point in the calibration curve divided by the counts of the ISTD at the same level; similarly, blank = analyte- to-ISTD intensity ratio, which is the measured count of the blank standard solution data point in the calibration curve divided by the counts of the ISTD at the same level as the blank standard solution; a = slope of the calibration curve (mL/ng); and DF = dilution factor, or the volume of the sample solution (mL) divided by sample weight (g). References: J. AOAC Int . 98 , 1711(2015) DOI: 10.5740/jaoacint.15-142 (First Action) J. AOAC Int . 101 , 536(2018) DOI: 10.5740/jaoacint.17-0318 (Final Action) AOAC SMPR 2014.004 J. AOAC Int . 98 , 1042(2015) DOI: 10.5740/jaoac.int.SMPR2014.004 Posted: February 19, 2016 (First Action); February 2018 (Final Action); April 2018; 2019 (Codex adoption) For Final Action status (2017), the First Action method (2015) was revised to add references to the dairy products in the title, scope, and other sections. Additional minor edits were made to clarify that sample duplication is not required and to reference the MLT published in J. AOAC Int. Importantly, Table 2015.06A was added to summarize and clarify the recommended analytical range of the method, which is derived from data presented in Thompson, J., & Pacquette, L. (2017) J. AOAC Int. 100 , 522–531 (DOI: 10.5740/jaoacint.16-0325). Although the PLOQ of the ICP- MS does not meet SPIFAN SMPR for Cu, Mn, and Fe, note that the LOQ (about 10 times lower) does meet all SMPR and Codex criteria.

= + a blank Y x Note that, the sample blank is identical to the Cal Blk in this method and is essentially zero because high-purity reagents are used. The analyte concentration in the sample is calculated: = − × x y blank a DF Table 2015.06D. Typical ICP-MS parameters for Agilent 7700x RF power, W a 1600 RF matching, V b 1.8 Sampling depth, mm 9 Extract 1 lens, V 0 Carrier gas, L/min 0.9 Make-up gas, L/min 0.2 Nebulizer (glass concentric) MicroMist Spray chamber temp., °C 2 Interface cones Ni He cell gas flow rate, mL/min 4.5 H 2 cell gas flow rate, mL/min 4.2 Nebulizer pump rate, rps 0.1 (0.5 mL/min) Peristaltic pump tubing White/white, 1.02 mm id Drain tubing Blue/yellow, 1.52 mm id a  The isotopes used for analysis are 23 Na, 24 Mg, 31 P, 39 K, 44 Ca, 52 Cr, 55 Mn, 56 Fe, 63 Cu, 66 Zn, 78 Se, and 95 Mo, with 72 Ge and 130 Te as internal standards. b  RF = Radiofrequency.

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