Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:7:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 7 (pt 1/2)
Character Range: 783768–787068

7                   Metals

7.1              Aqua regia digestible metals

    7.1.1         Scope and application
Method AS 4479.2-1997 may be used to obtain extracts from soils for the analysis of most metals and metalloids. Extracts obtained here are not suitable for speciation studies, and analysis of the extracts does not necessarily result in total or bioavailable heavy metal levels in a soil.

Metals extractable by this digestion include metallic components adsorbed on soil particles, complexed by and adsorbed on organic matter, and soluble metal salts. Complete decomposition of the soil is not possible using aqua regia; therefore metals bound within part or most of the silicate matrix may not be fully recovered by this method.

Samples extracted by this method can be analysed for metals by a suitable spectrophotometric method, while accounting for likely interferences, for example, chlorides.

US EPA SW-846 Method 3050B, SW-846 Method 3051A (microwave-assisted digestion) or Method 200.2 may be used as alternatives to this method.

    7.1.2         Principle
Boiling aqua regia (3:1 hydrochloric/nitric acid) is used to extract metals from soil. This concentrated acid mixture can extract inorganic metals as well as those bound in organic or sulfide forms.

7.2              Acid digestible metals in sediments, sludges and soils

    7.2.1         Scope and application
This method (US EPA SW-846, Method 3050B) may be used to prepare extracts from sediments, sludges and soils for the analysis of metals by various common spectrophotometric techniques.

It can be used to determine the following extracted metals:

FAAS/ICP-AES  GFAAS/ICP-MS

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

FAAS    =  Flame atomic absorption spectroscopy
GFAAS   =  Graphite furnace atomic absorption spectroscopy
ICPAES   =  Inductively coupled plasma atomic emission spectroscopy
ICPMS   =  Inductively coupled plasma mass spectrometry

    7.2.2         Principle
Two separate digestion procedures, whose extracts are not interchangeable for each other's determinations, are provided for determination of the above elements.

7.2.2.1         For FAAS and ICPAES
The field-moist or dry sample is digested at 95°C in nitric acid and hydrogen peroxide until the volume is reduced, or heated for two hours. Hydrochloric acid is then added and the mixture digested further at heat.
For improved solubility and recovery of antimony, barium, lead and silver, an optional nitric acid/hydrochloric acid digestion step may be used when necessary.

7.2.2.2         For GFAAS and ICPMS
The field-moist or dry sample is digested at 95°C in nitric acid and hydrogen peroxide until the 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