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Aromatic-hydrogen counting in tocopherol identification uses unoccupied ring positions to constrain the identity or composition of a tocopherol sample. In the tocol framework, positions 5, 7 and 8 can carry the additional methyl substituents. The familiar alpha-tocopherol, beta-tocopherol, gamma-tocopherol and delta-tocopherol substitution patterns leave respectively zero, one, one and two hydrogens at those positions.^[ref]

Let $k$ count those aromatic methyl substituents. The count $n_{\mathrm{arH}}=3-k$ concerns aromatic carbon-bound hydrogens. It excludes the hydroxyl hydrogen and hydrogens on the saturated ring and side chain. A missing aromatic hydrogen is not a missing hydrogen atom from the entire molecular formula: replacing ring H by $\mathrm{C}{\mathrm{H}}_3$ adds two hydrogens overall.

A proton nuclear magnetic resonance experiment can compare an integrated aromatic region with a calibrated amount standard. For a sufficiently resolved, quantitatively acquired signal, integrated response tracks the number of contributing protons; the count does not predict the number of separately resolved peaks. Chemical shifts, splitting, spectral overlap and acquisition conditions remain part of identification.

An original mixture example illustrates mixture ambiguity in aromatic-proton counts. Suppose the calibrated aromatic response corresponds to $r=1.30$ hydrogens per tocopherol molecule. If the sample contains only beta-tocopherol and delta-tocopherol, and $x$ is the mole fraction of delta-tocopherol, then $r=(1-x)+2x=1+x$, giving $x=0.30$. The same count occurs in a gamma-tocopherol/delta-tocopherol mixture. If the allowed components are instead alpha-tocopherol and delta-tocopherol, $r=2x$ gives $x=0.65$. Counting alone does not identify an unrestricted mixture.

In particular, beta-tocopherol and gamma-tocopherol are constitutional isomers with one remaining aromatic hydrogen each, at different ring positions. Their count agrees while their structural assignment differs. A useful experiment therefore combines the aromatic integral with resolved chemical shifts or other structural evidence and specifies which candidate components were allowed. These are predictions from the named structures, not measured spectra or universal instrumental settings.