title: Measurement of labile Cu in soil using stable isotope dilution and isotope ratio analysis by ICP-MS.
abstract: Isotope dilution is a useful technique to measure the labile metal pool, which is the amount of metal in soil in rapid equilibrium (<7 days) with the soil solution. This is normally performed by equilibrating soil with a metal isotope, and sampling the labile metal pool by using an extraction (E value), or by growing plants (L value). For Cu, this procedure is problematic for E values, and impossible for L values, due to the short half-life of the 64Cu radioisotope (12.4 h), which makes access and handling very difficult. We therefore developed a technique using enriched 65Cu stable isotope and measurement of 63Cu/65Cu ratios by quadrupole inductively coupled plasma mass spectrometry (ICP-MS) to measure labile pools of Cu in soils using E value techniques. Mass spectral interferences in detection of 63Cu/65Cu ratios in soil extracts were found to be minimal. Isotope ratios determined by quadrupole ICP-MS compared well to those determined by high-resolution (magnetic sector) ICP-MS. E values determined using the stable isotope technique compared well to those determined using the radioisotope for both uncontaminated and Cu-contaminated soils.
authors.affiliation: Centre for Environmental Contaminants Research, CSIRO Land and Water, PMB 2, Glen Osmond, SA 5064, Australia. annette.nolan@measurement.gov.au
authors.forename: Annette L
authors.initials: AL
authors.lastname: Nolan
authors.forename: Yibing
authors.initials: Y
authors.lastname: Ma
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
authors.forename: Mike J
authors.initials: MJ
authors.lastname: McLaughlin
mesh_terms: D003300:Copper / Q000032:analysis*; D007201:Indicator Dilution Techniques; D007554:Isotopes / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis; D013997:Time Factors; D014873:Water Pollutants / Q000032:analysis
chemical_list: D007554:Isotopes; D012987:Soil; D012989:Soil Pollutants; D014873:Water Pollutants; D003300:Copper