Optimizing MC-ICP-MS with SEM protocols for determination of U and Th isotope ratios and 230Th ages in carbonates

Publication type

Journal Article

Research Area


Research Team

Isotope Geochemistry


We have optimized techniques to measure uranium and thorium isotopic compositions using secondary electron multiplier (SEM) and peak-jumping protocols on a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS, Thermo Scientific Neptune Plus). This instrument is equipped with an advanced interface pump, X- skimmer cone, Jet sample cone, and desolvating nebulizer system (CETAC Aridus II) that enables overall ioni- zation and transmission efficiency up to 3% for both U and Th. Approximately 50 fg 234U or 230Th can routinely yield a precision of 1–2‰ (2σ) for abundance and isotopic measurements. Non-linear behavior was not observed in the MasCom SEM with a retarding potential quadrupole in our MC-ICP-MS system when the beam intensity was limited to < ∼1="" ×="" 106="" cps.="" we="" performed="" a="" series="" of="" tests="" to="" examine="" the="" influence="" of="" tuning="" parameters,="" peak="" shift,="" and="" operating="" voltage="" of="" the="" sem="" on="" isotopic="" measurements.="" results="" for="" u/th="" standards="" are="" consistent="" with="" published="" values="" and="" demonstrate="" the="" reliability="" of="" our="" protocols.="" lastly,="" the="" precision="" and="" accuracy="" of="" 230th="" ages="" based="" on="" u="" and="" th="" isotope="" ratios="" is="" presented="" for="" a="" variety="" of="" carbonates,="" including="" both="" modern="" and="" secular-equilibrium="" samples.="" for="" corals="" as="" young="" as="" ∼10-yr="" old,="" we="" have="" significantly="" reduced="" the="" procedural="" chemistry="" blanks="" so="" that="" only="" 40="" mg="" is="" required="" to="" yield="" an="" analytical="" precision="" of="" ±="" 1.4="" yr="" (2σ).="" all="" 230th="" ages="" from="" modern="" and="" fossil="" corals="" and="" speleothems="" are="" in="" agreement="" with="" band="" counting="">

Publication Details


Quaternary Geochronology





Date Published


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