Attached Proton Test (APT)

Introduction:

The APT (Attached Proton Test) experiment is a modification of the SEFT experiment, in that it differentiates between C, CH, CH2, and CH3 groups. After the transformation, the CH and CH3 carbons will have the opposite phase from the quaternary and CH2 carbons.  Alternate methods in determining the multiplicity of the carbon center are INEPT, DEPT, PENDANT, and the old off-resonance 1H decoupling technique experiments.  Unlike these experiments, the APT method yields only NOE enhancements and also gleans information about quaternary carbon atoms.
 
References:
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  • J.C. Madsen, H. Bildsoe, H. Jakobsen, O.W. Sorensen, J. Mag. Res. 1986, 67, 243-57.
  • A.M. Torres, T.T. Nakashima, R.E.D. McClung, J. Mag, Res. Ser. A 1993, 101, 285-94.