AOAC OMA# 2011.14 (Final Action Review)-OMB

2011.14 (Oct. 2018) – MTE-03 Final Action Review FOR ERP USE ONLY DO NOT DISTRIBUTE

autosampler tubes. Dilute to volume with H 2 O and mix. [ Note : Final dilutions in volumetric flasks (e.g. 50 mL) or autosampler tubes (e.g. 25 mL) require the addition of appropriate amounts of combined acids for MDO to maintain the proportion of 15%, v/v, combined acids and hydrogen peroxide in the final solution to be analyzed.] ( Note : A digestion is judged complete when a clear to yellow analytical solution is produced.) ( 3 ) Filter the digested solution using an ashless filter paper for turbid samples containing fat. Discard the first 20 mL filtrate and collect the remaining filtrate for analysis. [ Note : Membrane disc filters (0.45 µm) are not recommended as they are generally not metal-free.] ( 4 ) Transfer to polyethylene containers within 2 h. ( 5 ) If samples are found to be above the standard curve range or have a total content of minerals higher than 1000 mg/L, dilute with H 2 O. [ Note : Final dilutions require the addition of appropriate amounts of HNO 3 for MDC digests (or appropriate amounts of combined acids for MDO) to maintain the proportion of 10% (v/v) HNO 3 (15%, v/v, combined acids and hydrogen peroxide) in the final solution to be analyzed.] ( f ) Digestion vessel decontamination .—Decontaminate used MDC vessels with 5 mL HNO 3 according to a program close to that in e ( 1 ). Dry MDC vessels at 60°C in drying oven for 1 h. Wash the MDO glass volumetric flasks or tubes in a laboratory washing machine or soak overnight in a water bath with HNO 3 (30%, v/v). Rinse with H 2 O to avoid or to minimize risk of iron contamination.

E. Determination

( a ) ICP-AES setup.– Ionization buffer (cesium chloride) is combined with the internal