The Importance of Isotopes

This week we celebrate Frederick Soddy, an English pioneer in nuclear chemistry and atomic science, who was born September 2, 1877.  Working with Ernest Rutherford, he studied radioactive decay and coined the term “half-life.”

Soddy also theorized in 1912 that some elements could be chemically identical but have different atomic structures.  He called this concept an “isotope” (after isos topos, Greek for “same place”).  His theory remained controversial until it was confirmed by the discovery of the neutron in 1932.

(Uranium is an example.  U-235 and U-238 both contain 92 protons, but U-238 has three extra neutrons and is more stable.  Nuclear power reactors work by “enriching” or increasing the percentage of U-235, which is more easily fissioned or split.)

After receiving the 1921 Nobel Prize in Chemistry, Soddy grew frustrated with science and became a social advocate.  He criticized scientists for ignoring the moral and ethical consequences of their work, including his own work on radioactivity.   He argued that science could produce enough food and health care for the entire world, but that economic systems promoted inequality.  He saw the tragic consequences of the first atomic bombs in World War II.  Sadly, Soddy and his wife were never able to have children; his work with radioactivity had rendered him sterile.

Today, isotopes are a fundamental part of science.  Isotopes are used in carbon-14 dating, a method for calculating geological age.

Isotopes can determine the quality of Traditional Chinese Medicine.  A TCM’s effectiveness is highly dependent on the source of origin of its herbal components.  Scientists have used an Agilent ICP-MS to measure lead (Pb) isotope ratios in Dan-shen, an herb used in TCM.  By comparing this data to water and soil samples, they can distinguish Dan-shen samples originating from different geographical areas.

Isotopes can even indicate the amount of milk an infant consumes while breastfeeding, which is important to health professionals in third-world countries.  Nonradioactive deuterium oxide (2H2O) can be passed from mother to child through breast milk.  An Agilent FTIR can measure the amount of 2H2O in the infant’s saliva, providing a portable and low-cost method to determine the amount of milk she has consumed.

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