CHAPTER XVI 



STABLE ISOTOPES AS TRACERS 



Fred M. TJber, Iowa State College 



A . Fundamental Basis of Stable Isotope Methods 562 



1 . Principles and Underlying Assumptions 562 



2 . Theory of Measurement 563 



3. When Should Stable Instead of Radioactive Isotopes be 



Used? 564 



B . Potential Research Applications 566 



1 . Diffusion and Transport Studies 566 



2 . Mechanisms of Biochemical Reactions 567 



3 . Rates of Biological Processes 568 



4 . Quantitative Analysis 568 



5 . Gas Analysis 570 



C . Demands on Equipment and Technical Skill 571 



1 . Availability of Concentrated Isotopes 571 



2 . Synthesis of Isotopic Compounds 572 



3. Apparatus for Detecting Stable Isotopes 574 



4. Preparation of Samples for Analysis 578 



5. Measurements and Maintenance 581 



6. Calculation of Results 583 



D . Limitations and Sources of Error 586 



1 . Absolute Accuracy of Isotope Concentrations 586 



2. Relative Accuracy 587 



3. Natural Variations in Isotope Concentrations 589 



4 . Minimum Size of Test Samples 590 



5. Limiting Dilution Factors 590 



6 . Exchange Reactions 591 



7 . Interfering Particles 592 



8 . Standard Samples for Comparison 593 



9 . Over- All Accuracy 594 



E. Accomplishments with Individual Elements 594 



1 . Deuterium and Heavy Water 594 



2. Carbon 595 



3. Nitrogen 595 



4 . Oxygen 595 



5. Sulfur 596 



References 596 



561 



