Metal Speciation

ALS - Columbia's metal speciation services include: mercury speciation, arsenic speciation, selenium speciation, chromium speciation and speciation for other low-level trace metals. The analysis of these metals can provide valuable information on toxicity, such as how it may be transferred into living organisms, along with transportation considerations, bioavailability, risk assessment and remedial investigations.

Metal speciation is the determination of the form(s) of an element in a sample. This might be limited to speciating by valence of an inorganic form (e.g. hexavalent chromium vs. trivalent chromium vs. total chromium), or it might include speciating by valence and/or combined form(s) (e.g. elemental mercury vs. mercuric ion vs. methyl mercuric ion).

Metal Speciation Capabilities

• Trace-metals speciation - The various procedures commonly include mercury speciation, arsenic speciation, chromium speciation, and/or tin speciation. Other applications are evaluated on a case to case basis.
• Ultra-low level quantification - Aqueous measurements are in pg/L (ppq) to ng/L (ppt) range, solid phase measurements in the pg/g (ppt) and ng/g (ppb) range. Ultra-clean sampling and analysis protocols are consistent EPA Method 1699M.
• Analysis of difficult matrices - Preparation of  hydrocarbons, coal, polymers, biota, and other complex matrices are given special consideration relative to complete dissolution and/or digestion, as well as preserving the metal species during the preparation process.  
• Analytical methods development - Several procedures have been developed or refined by CAS staff. Evaluation and development of procedures to meet the requirements of specific applications is available.

Types of Metal Speciation

• Chemical Speciation
  • Molecular (combined) forms (CH₃Hg⁺¹, Bu₃Sn⁺¹, etc.)
  • Oxidation State (valence) species [As(lll), As(V), etc.]
  • Ionic-ligand Complexes [HgCl⁺¹, HgCl₂⁰, HgCl₃^-1, etc.
• Physical Speciation
  • Gaseous species [Hg⁰, (CH₃)₂Hg, AsH₃, etc.]
  • Dissolved species [Hg⁺², HgCl⁺¹, HgCl₂, etc.]

Instruments & Technology in use:

• HG-GC-AAS (Hydride Generation - Gas Chromatography - Atomic Absorption Spectrometry)
• CVAFS (Cold Vapor Atomic Fluorescence Spectrophotometry)
• IC-ICP/MS (Ion Chromatography - Inductively Coupled Plasma - Mass Spectrometry)
• Chemical Separation/ICP/MS (Various chemistries to produce a solution suitable for Inductively Coupled Plasma - Mass Spectrometry)
• Chemical Separation/GFAAS (Various chemistries to produce a solution suitable for Graphite Furnace Atomic Absorption Spectroscopy)
• Chemical Separation/ICP-OES (Various chemistries to produce a solution suitable for Inductively Coupled Plasma – Optical Emission Spectroscopy)
• Chemical Separation/GC/AFS (Derivatization followed by Gas Chromatography separation and subsequent detection via Atomic Fluorescence Spectroscopy)

Related links:

Metals testing for RoHS/WEEE compliance

Mercury testing

Methylmercury testing

Metals testing articles