Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:7:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 7 (pt 2/2)
Character Range: 786776–789648

volume is reduced, or heated for two hours.

7.3              Metals by microwave assisted acid digestion of sediments, sludges, soils and oils

    7.3.1         Scope and application
This method (US EPA SW-846, Method 3051A) describes a rapid acid-assisted microwave procedure for digesting sediments, sludges, soils and oils for the analysis of most metals, some metalloids and some non-metals, including (but not limited to):

Aluminium   Cadmium    Iron        Molybdenum   Sodium
Antimony    Calcium    Lead        Nickel       Strontium
Arsenic     Chromium   Magnesium   Potassium    Thallium
Barium      Cobalt     Manganese   Selenium     Vanadium
Boron       Copper     Mercury     Silver       Zinc
Beryllium

    7.3.2         Principle
The sample is digested in concentrated nitric acid, or a mixture of nitric and hydrochloric acids, using microwave heating in a sealed Teflon™ vessel at elevated temperature and pressure. The final digest can be analysed for the element by various common spectrophotometric methods, as described in US EPA Method 3051A.

7.4              Mercury

    7.4.1         Scope and application
This method (US EPA SW-846, Method 7471B) may be used as an alternative to methods described in this Schedule for mercury. It uses strong acid digestion (aqua regia) to determine total mercury (inorganic and organic) in soils, sediments, bottom deposits and sludge-type materials.

    7.4.2         Principle
Mercury is digested with aqua regia (1:3 nitric acid/hydrochloric acid) at 95°C in the presence of a strong oxidant (potassium permanganate). The digest is then analysed by cold-vapour atomic absorption spectrometry.

CAUTION: Mercury vapour is highly toxic. Use appropriate safety precautions ensuring the mercury vapour is vented into an appropriate exhaust hood or, preferably, trapped in an absorbing medium (e.g. potassium permanganate/sulfuric acid solution).

Note: US EPA Method 1630 may be used for methyl mercury.

7.5              Hexavalent Chromium

    7.5.1         Scope and application
This method (US EPA SW-846, Method 3060A) is an alkaline digestion procedure for extracting hexavalent chromium [Cr (VI)] from soluble, adsorbed and precipitated forms of chromium compounds in soils, sludges, sediments and similar waste materials.

    7.5.2         Principle
The method uses an alkaline digestion to solubilise both water-soluble and water-insoluble Cr(VI) compounds. The pH should be carefully monitored during digestion to prevent reduction of Cr(VI) or oxidation of native Cr(III).

Cr(VI) in the digest can then be determined colourimetrically by UV visible spectrophotometry (US EPA SW-846, Method 7196), ion chromatography (US EPA SW-846, Method 7199) or other suitable validated methods.

CAUTION: Cr(VI) is highly toxic. Use appropriate safety precautions when handling and disposing of waste.