AOAC Final Action Methods in 2019

to a final weight of 5.0 g into a suitable plastic container. Mix well prior to weighing into the 55 mL MarsExpress vessel. ( b ) A reagent blank, a reagent blank + IS, and working standards must be included for each analysis and treated the same as samples through the analysis. Add 50 μL of each working solution to separate 50 mL Digitubes. The final nominal concentrations for these after they have gone through the sample preparation (diluted 1000X) are listed in the Standard Solutions Preparation section to be used for construction of the calibration curve. ( c ) Add 50 μL intermediate mixed IS solution to each sample, IWS, and reagent blank + IS. ( d ) Add 5 mL MS grade water and 2.5 mL of 70% (w/w) nitric acid with a bottle top dispenser. Cap tightly or utilize a capping station. Mix the sample by either vortexing or inverting. ( e ) Insert vessels into their appropriate sleeves and into the turntable. Microwave samples according to the following conditions: Power 1000 W; ramp to temperature 10 min; hold time 40 min; temperature 120°C. ( f ) Allow vessels to complete the cooling process in the microwave before removing caps to prevent loss of sample through pressure release. ( g ) Quantitatively transfer contents of the vessels into 50 mL Digitubes with MS grade water and dilute to a volume of 25 mL with MS grade water. ( h ) Filter samples through a 0.45 μm PTFE syringe filter into a microcentrifuge tube. Standards do not need to be filtered through the syringe filter. ( i ) If dilutions are required, dilute samples to appropriate concentrations using the reagent blank + IS utilizingmicrocentrifuge tubes to do the dilutions. ( j ) Aliquot 0.5 mL extract into a silanized injection vial, along with 0.5 mL acetonitrile. Cap and then mix well by shaking or

vortexing the vials. Prepared sample extracts in injection vials are stable for 24 h while stored 2–8°C and protected from light. ( d )  Instrument parameters .— See Tables 2015.10B and 2015.10C . F. Calculations Integrate the peak areas of the analytes and IS in both the sample and standard injections. Peak areas of reference standard analyte quantitation ions are divided by the corresponding IS peak areas to obtain relative analyte responses (normalized to IS). Relative responses of each analyte in the calibration standards are plotted on the y -axis against their corresponding concentrations on the x -axis to generate calibration curves with linear fit and 1/x2 weighting for all compounds. Analyte concentrations in the sample extracts are derived from the calibration curves and their concentrations in the samples are determined using the following equation: ( C × V × D ) / ( W × 1000) = mg/kg where C = analyte concentration in sample (ng/mL); V = final volume (mL); D = dilution (mL/mL); W = sample weight (g); and DOI: 10.5740/jaoacint.15-0144 (First Action) AOAC SMPR 2012.010 J. AOAC Int. 96 , 488(2013) DOI: 10.5740/jaoac.int.SMPR2012.010 AOAC SMPR 2012.013 J. AOAC Int. 96 , 492(2013) DOI: 10.5740/jaoac.int.SMPR2012.013 Posted: February 19, 2016 (First Action), August 2019 (Final Action) 1000 = conversion from ng/g into mg/kg. References: J. AOAC Int . 99 , 204(2016)

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