Because elemental and molecular mass spectrometry typically use different ionization methods, 

they usually need to be done on separate instruments. R. Kenneth Marcus of Clemson 

University, David W. Koppenaal of the Environmental Molecular Sciences Laboratory and the 

Pacific Northwest National Laboratory, and their coworkers now report that they can perform 

mass spectrometry of elemental and organometallic species with resolving power in excess of 1 

million using a combined atomic and molecular ionization source coupled to an Orbitrap mass 

analyzer.The combined device, called the liquid sampling–atmospheric pressure glow discharge 

source, uses a microplasma for ionization. Using the system, the researchers were able to 

resolve important inorganic compounds that have been difficult to study. For the first time, the 

researchers isotopically resolved a bimetallic amino acid complex, Hg:Se-cysteine, that is 

believed to be involved in mercury detoxification. The researchers also used the system to 

resolve 87Rb and 87Sr, whose mass difference reflects the β decay of radioactive 87Rb to the 

stable isotope 87Sr. Their ratio is used in geological dating. “Ionization sources like this will allow 

inorganic mass spectrometry to benefit from the high resolving power that molecular mass 

spectrometry has been enjoying for many years,” says Steven Ray, an atomic mass 

spectrometrist at the University at Buffalo.