AOAC Final Action Methods in 2018

microwave systems. Never remove hot vessels from microwave; wait until they are near room temperature. Keep microwave door closed while vessels are hot. The door is the primary safety device if a vessel vents. See Tables 2011.14A – I for results of the interlaboratory study supporting acceptance of the method. [ Note : Results shown in Tables 2011.14A – I are slightly different from those shown in J. AOAC Int . 92 , 1484(2009) due to classical statistics applied instead of robust statistics applied in the tables included in J. AOAC Int . 95 , 177(2012).] See Table 2011.14J for results of the interlaboratory study by element for AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) fortified products and SPIFAN placebos compared to AOAC Standard Method Performance Requirement (SMPR ® ) 2014.004. A. Principle Test portion is heated at 200°C either with nitric acid in a closed- vessel microwave digestion system (MDC) or with a combination of hydrogen peroxide, nitric acid, and hydrochloric acid in an open- vessel microwave digestion system (MDO). Digested test solution or an appropriate dilution is presented to the inductively coupled plasma-atomic emission spectrometry (ICP-AES) instrument. The instrument is calibrated with acid(s) matched standard calibration solutions. An ionization buffer (cesium) and internal standard(s) (chromium, indium, strontium, and yttrium) are used with or without appropriate in-line addition to minimize easily ionizable element (EIE) effects and to correct for physical and chemical ( Note : ICP-AES equipment must be used by qualified laboratory personnel who are familiar with the operation and maintenance of analytical systems and must follow manufacturer’s directions for safety risk, safety environment, and use of instruments.) ( a )  Microwave . ____ Commercial MDC or MDO designed for laboratory use at 200 ± 20°C, up to 600 psi, with operator selectable output of 0–1800 W microwave power, controlled temperature and pressure ramping capability, and equipped with appropriate vessels with a capacity of minimum 50 mL (e.g., 75 mL). It is recommended that vessel design be selected that will withstand the maximum possible pressure (600 psi) because organic residues of rich-fat or rich-carbohydrate samples, if not given sufficient time to predigest, will generate significant pressure during digestion. ( b )  MDC vessels or MDO flasks or tubes . ( c )  Analytical balance .—Capable of weighing ±0.1 mg. ( d )  Volumetric flasks .—Class A, glass, assorted sizes. ( e )  Volumetric pipets .—Class A, glass, assorted sizes. ( f )  Micropipets .—Adjustable, 0.100–1.000 mL and 1–5 mL with disposable plastic tips. ( g )  Dispenser .—Capable of dispensing 1–10 mL. ( h )  High-density polyethylene bottles .—For storing standard and sample solutions. ( i )  Water baths .—Capable of maintaining 20 ± 2°C and 40 ± 2°C. ( j )  Grinding device . ( k )  ICP-AES spectrometer .—Instrument with axial, radial, or dual view grating configurations and autosampler, capable of determining multiple wavelengths for each element of interest with the required sensitivity. A 3-channel peristaltic pump with interferences. B. Apparatus

AOAC Official Method 2011.14 Minerals and Trace Elements in Milk and Milk Products, Infant Formula,

and Adult Nutritionals Microwave Digestion and Inductively Coupled Plasma-Atomic Emission Spectrometry First Action 2011 Final Action 2013 (Fortified Food Products) Revised First Action 2017 Final Action 2018 (Infant Formula and Adult Nutritionals) [Applicable to determination of calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P), sodium (Na), and zinc (Zn) in chocolate milk powder, dietetic milk powder 2, infant cereal, peanut butter, wheat gluten, milk, dried milk, butter, cheese, whey, dried whey, infant formula, and adult nutritionals.] Upper limits (mg/kg) for chocolate milk powder, dietetic milk powder 2, infant cereal, peanut butter, and wheat gluten: Ca (24000); Cu (210); Fe (850); K (32000); Mg (7500); Mn (20); Na (16000); P (16000); Zn (320). Limits of quantitation (LOQs; determined as 10*s r of the mean of 10 measurements of the low standard solution, Std1, mg/kg) for chocolate milk powder, dietetic milk powder 2, infant cereal, peanut butter, and wheat gluten: Ca (150); Cu (2); Fe (10); K (200); Mg (50); Mn (0.05); Na (100); P (100); Zn (5). Upper limits (mg/100 g) for ( 1 ) milk and ready-to-feed (RTF) liquids as-is using a typical sample size of 4 g per final analytical solution volume of 25 mL and ( 2 ) reconstituted milk powder, infant formula powders, and adult nutritional powders (25 g into 200 g water), using a typical sample size of mass of the reconstituted slurry per final analytical solution volume of 25 mL: Ca (1280); Cu (1.2); Fe (20); K (2000); Mg (110); Mn (1.0); Na (850); P (800); Zn (18). LOQs (determined as the mean of blanks + 10*s r ; mg/100 g) for ( 1 ) milk and RTF liquids as-is using a typical sample size of 4 g per final analytical solution volume of 25 mL and ( 2 ) reconstituted milk powder, infant formula powders, and adult nutritional powders (25 g into 200 g water), using a typical sample size of mass of the reconstituted slurry per final analytical solution volume of 25 mL: Ca (0.1); Cu (0.003); Fe (0.05); K (1.5); Mg (0.02); Mn (0.001); Na (0.1); P (0.01); Zn (0.003). Limits for nonreconstituted dairy ingredients (butter, cheese, whey powders, whey protein concentrates) shall be adjusted proportionally upward from these values based upon the sample size used for the ingredient. For example, if 0.6 g cheese is digested, the limits will be 4 g/0.6 g = 6.7-fold higher. Caution : Before using chemicals, refer to the supplier guide for chemical safety and/or other adequate manuals or safety data sheets approved by local authorities. Use fume hood and wear full personal laboratory protective clothing, gloves, and appropriate eye protection (safety glasses) when using glassware and preparing standards or test portions with acid solutions. Application of microwave digestion systems involves hot pressurized acid solutions and concentrated acids. Use fume hood and wear full personal laboratory protective clothing, gloves and appropriate eye protection (safety glasses) when using glassware and preparing standards or samples with acid solutions. Follow manufacturer’s directions for safety risk and safety environment of

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