AOAC OMA# 2011.14 (Final Action Review)-OMB

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

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 interferences.

B. Apparatus

( 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) since 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.